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Potential applications of human artificial skin and electronic skin (e-skin): A review

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Abstract

There is an ever-increasing need to develop artificial skin that can fully mimic the human skin that it replaces. Skin substitutes have been commercialized and are used in cosmetics and wound healing treatment, with mixed results obtained. Apart from artificial skin, electronic skin (e-skin) is also widely researched because it can be customized into wearable devices. E-skin is commonly characterized by its flexibility and ability to accommodate a wide range of sensors in ultrathin films. This paper reviews the current development and technology applied to artificial skin and e-skin. First, the basic layers of the normal human skin are introduced. Then, the current development of artificial skin in cosmetics and grafting applications are mentioned in one section. The latest technology in the fabrication of e-skin and some of its characteristics in different applications are also discussed. The ban on the use of animals for testing cosmetics and its positive effects on the development of alternatives to animal testing in experiments are also explained in this paper. Lastly, the current challenges in skin research and recommendations for future applications of artificial skin as well as e-skin are presented.

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... Human skin can sense a variety of external stimuli through tactile and contactless modes, and has the characteristics of flexibility, stretchability, a broad pressure sensing range (2 kPa -1 MPa), and a fast response time (15 ms) [1][2][3][4]. Electronic skin (e-skin) has important applications in robotics [1], prosthetics [1,2], medical monitoring [2], wearable equipment [4][5][6], etc [7][8][9]. Due to the trend of miniaturization and integration in smart flexible electronics, the demand for e-skin that can comprehensively mimic multiple functions and the sensing capabilities and characteristics of human skin has urgently arisen. ...
... Human skin can sense a variety of external stimuli through tactile and contactless modes, and has the characteristics of flexibility, stretchability, a broad pressure sensing range (2 kPa -1 MPa), and a fast response time (15 ms) [1][2][3][4]. Electronic skin (e-skin) has important applications in robotics [1], prosthetics [1,2], medical monitoring [2], wearable equipment [4][5][6], etc [7][8][9]. Due to the trend of miniaturization and integration in smart flexible electronics, the demand for e-skin that can comprehensively mimic multiple functions and the sensing capabilities and characteristics of human skin has urgently arisen. ...
... Human skin can sense a variety of external stimuli through tactile and contactless modes, and has the characteristics of flexibility, stretchability, a broad pressure sensing range (2 kPa -1 MPa), and a fast response time (15 ms) [1][2][3][4]. Electronic skin (e-skin) has important applications in robotics [1], prosthetics [1,2], medical monitoring [2], wearable equipment [4][5][6], etc [7][8][9]. Due to the trend of miniaturization and integration in smart flexible electronics, the demand for e-skin that can comprehensively mimic multiple functions and the sensing capabilities and characteristics of human skin has urgently arisen. ...
Article
Electronic skin (e-skin) has significant application prospects in soft robotics, prosthetics, medical monitoring, and wearable equipment. However, it remains a great challenge for e-skin to comprehensively mimic the multifunctional sensing capabilities and characteristics of human skin. Herein, vertical graphene arrays (VGA) were directly fabricated on the surface of a natural latex film using a facile method. The e-skin based on VGA combines the intrinsic properties of graphene and flexible substrates, as well as the morphological advantages of VGA, giving it multifunctional sensing capabilities similar to those of human skin. The e-skin not only exhibited multifunctional tactile perception of the pressure, airflow, and surface morphology of objects, but could also percept the difference in temperature between the detected object and the e-skin in a noncontact manner. Moreover, the sensing characteristics, including an ultrafast responsiveness (6.7 ms) and resilience (13.4 ms), a broad pressure sensing range (2.5 Pa∼1.1 MPa), a high sensitivity, and a robust cyclability, further demonstrate the similarity to that of human skin. The outstanding stretchability of the substrate endows the e-skin with an ultrabroad strain detection range (0.5%∼250%). Furthermore, the e-skin can still maintain the VGA structure, as well as the sensing capability under large tensile deformations. The facile preparation methods and excellent performance mean this e-skin is expected to be applied as a multifunctional integrated e-skin in smart flexible electronics.
... The primordial utility of these skin models has been grafting. There are commercial artificial skin substitutes [25] and autologous BASS manufactured under GMP conditions [4,7] to treat patients with burns. Furthermore, these BASS are also being used to analyze and take measurements of the physiological features of human skin [25]. ...
... There are commercial artificial skin substitutes [25] and autologous BASS manufactured under GMP conditions [4,7] to treat patients with burns. Furthermore, these BASS are also being used to analyze and take measurements of the physiological features of human skin [25]. Currently, there are also BASS designed to model skin diseases, which gives researchers and doctors access to closely analyze the disease at various levels. ...
Article
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This review aims to be an update of Bioengineered Artificial Skin Substitutes (BASS) applications. At the first moment, they were created as an attempt to replace native skin grafts transplantation. Nowadays, these in vitro models have been increasing and widening their application areas, becoming important tools for research. This study is focus on the ability to design in vitro BASS which have been demonstrated to be appropriate to develop new products in the cosmetic and pharmacology industry. Allowing to go deeper into the skin disease research, and to analyze the effects provoked by environmental stressful agents. The importance of BASS to replace animal experimentation is also highlighted. Furthermore, the BASS validation parameters approved by the OECD (Organisation for Economic Cooperation and Development) are also analyzed. This report presents an overview of the skin models applicable to skin research along with their design methods. Finally, the potential and limitations of the currently available BASS to supply the demands for disease modeling and pharmaceutical screening are discussed.
... E-skin serves as a crucial platform for realizing the tactile perception of artificial limbs [95], intelligent robots [96], and wearable HMI terminals [97]. Achieving conformality and ensuring optimal wearing comfort are critical considerations in the application of TCLE in e-skin. ...
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The growing demand from the extended reality and wearable electronics market has led to an increased focus on the development of flexible human-machine interfaces (HMI). These interfaces require efficient user input acquisition modules that can realize touch operation, handwriting input, and motion sensing functions. In this paper, we present a systematic review of triboelectric-based contact localization electronics (TCLE) which play a crucial role in enabling the lightweight and long-endurance designs of flexible HMI. We begin by summarizing the mainstream working principles utilized in the design of TCLE, highlighting their respective strengths and weaknesses. Additionally, we discuss the implementation methods of TCLE in realizing advanced functions such as sliding motion detection, handwriting trajectory detection, and artificial intelligence-based user recognition. Furthermore, we review recent works on the applications of TCLE in HMI devices, which provide valuable insights for guiding the design of application scene-specified TCLE devices. Overall, this review aims to contribute to the advancement and understanding of TCLE, facilitating the development of next-generation HMI for various applications.
... Electronic skin, also known as e-skin, is a broad term used to refer to artificial skin that emulates human skin, not only for covering and protective purposes, but also for providing haptic, thermal and humidity sensations [5,143,144]. It has a wide range of potential applications, namely robotics, prosthetics, virtual reality, human/machine interfacing, monitoring vital signs, detecting environmental pollutants, and human skin replacement [144,145]. ...
Article
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It has increasingly been recognized that electrical currents play a pivotal role in cell migration and tissue repair, in a process named “galvanotaxis”. In this review, we summarize the current evidence supporting the potential benefits of electric stimulation (ES) in the physiology of peripheral nerve repair (PNR). Moreover, we discuss the potential of piezoelectric materials in this context. The use of these materials has deserved great attention, as the movement of the body or of the external environment can be used to power internally the electrical properties of devices used for providing ES or acting as sensory receptors in artificial skin (e-skin). The fact that organic materials sustain spontaneous degradation inside the body means their piezoelectric effect is limited in duration. In the case of PNR, this is not necessarily problematic, as ES is only required during the regeneration period. Arguably, piezoelectric materials have the potential to revolutionize PNR with new biomedical devices that range from scaffolds and nerve-guiding conduits to sensory or efferent components of e-skin. However, much remains to be learned regarding piezoelectric materials, their use in manufacturing of biomedical devices, and their sterilization process, to fine-tune their safe, effective, and predictable in vivo application.
... It is the biggest organ in the human body. Artificial electronic skin offers a broad variety of potential applications, including prosthetic limbs, robotics, mobile phones and computers touch screens, car steering wheels, medicine, and so on (Ma et al., 2017;Dolbashid et al., 2018;Rahman et al., 2020). As shown in Figure 8A, Yu Rim Lee et al. developed a sensitive artificial electronic skin inspired by Merkel cells . ...
Article
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Triboelectric nanogenerators are widely used in a variety of applications including wearable electronics, self-driven sensors, electrochemistry, and other fields. A lot of work has been done by researchers to increase the performance of triboelectric nanogenerators. Changing device structure, physical surface engineering and chemical composition modification are common effective methods. Some recent studies have found that the polarization of ferroelectric materials can regulate the output of triboelectric nanogenerators. Compared with other materials, ferroelectric materials have the advantages of polarization characteristics and large dielectric constant, which can improve the output performance by regulating the electric potential on the surface of the material, and can also collect the pyroelectric -piezoelectric-triboelectric coupling energy. However, most ferroelectric materials are rigid and therefore difficult to apply to flexible wearable electronics. In this paper, we briefly describe the mechanism of ferroelectric polarization triboelectric output and the working mechanism of coupled generators, then introduce some flexible ferroelectric materials and finally introduce some of their recent applications.
... Skin is the largest organ that not only protects our bodies from the environment, but also as a system senses and converts external stimuli into physiological signals 1 . The concept of electronic skin (e-skin) that represents a device to mimic natural skin, is developing explosively 2−4 and in order to be user friendly, it aims to rebuild the skin's sensing response to the vital characteristic, e.g. ...
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There is growing recognition that the developments in piezoresistive devices from personal healthcare to artificial intelligence, will emerge as de novo translational success in electronic skin. Here, we review the updates with regard to piezoresistive sensors including basic fundamentals, design and fabrication, and device performance. We also discuss the prosperous advances in piezoresistive sensor application, which offer perspectives for future electronic skin.
... In recent years, wearable and skin-mountable devices have received great attention due to their significant role in the development of real-time health diagnostics, therapeutics, and monitoring systems [1]. Recent advancements in the fabrication of materials with tunable dimensions facilitate us to realize such unique ultrathin devices with excellent mechanical flexibility and stretchability that can be conformally integrated with human skin [2]. In this view, various devices, including optoelectronic, electronic, sensor, energy, and drug transport & delivery devices, have been developed in the form of wristbands, gloves, socks, and adhesive patches [3]. ...
Article
In recent years, the development of weightless, ultrathin, and non-toxic devices has received tremendous interest owing to their potential applications as building blocks for various flexible, wearable, and skin-mountable systems. In this view, we explored the exceptional performances of flexible energy harvesters and storage devices along with wearable optoelectronic devices by adopting high-quality graphene monolayers and a user-friendly transfer methodology. Flexible and transparent energy generators with an active layer (AL) thickness of ∼20 μm and storage devices (AL≤ 1 μm) were developed by sandwiching the piezoelectric and solid electrolyte materials between two graphene monolayers, respectively. Wearable photosensors, with an AL thickness of ∼30 μm, were designed by integrating an ultrathin zinc oxide layer with a graphene monolayer. Under nominal mechanical movements, typical graphene monolayers-based piezoelectric energy generators exhibited very stable peak voltage and current density of 5.5 V and 0.2 nA/cm², respectively. Whereas the skin-mountable micro-supercapacitor (mSC) showed slightly lower areal and volumetric capacitances (6.3 μF/cm² and 91 mF/cm³@100 mV/s scan rate) than that of the flexible mSCs. Interestingly, these mSC devices also showed significant mechanical flexibility, stability, and durability. Further, the as-fabricated photosensors exhibited a strong response to visible light with an On/Off current density ratio of 1.8 and excellent wearability. Based on these demonstrated outcomes, we emphasize that the devices fabricated on different substrates by using graphene single layers could be adopted for various wearable, biocompatible, and skin-mountable devices that are widely being used in various health monitoring systems.
... 1 Skin relies on internal mechanical receptors to sense the intensity and position of surface physical stimulation and upload the perceived information to the brain. 2 There are five types of tactile receptors in human skin with different structures and functions, among which the Meissner body sensor and the Pasini body sensor are wrapped in a liquid-or gel-filled capsule. These liquids or gels increase the sensitivity of the tactile receptors. ...
Article
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An electronic skin (ES) is developed by embedding a liquid-core poly(vinylidene fluoride) fiber into a silicone rubber. The experimental results show that the ES can detect the waveform, frequency, amplitude, and other parameters of the surface vibration pressure. The ES can sense the surface pressure amplitude over a range of 1.5–2.5 kPa and exhibits a sensitivity of 0.0472 fC/Pa when the pressure is less than 60 Pa. The resonant frequency of the ES is 0.4 Hz. The ES can also detect the elongation strain, and its sensitivity is 0.0058 fC/με. The ES has the characteristics of flexibility, high sensitivity, and a wide measuring range. Therefore, the ES can be used as a robot finger skin, which enables the robot to have touch perception capabilities.
... Natural and synthetic skin substitutes are providing temporary and permanent effects. Electronic skin substitutes are used for sensing applications [1]. Stem cell treatment is used for infection and burn injuries, but it does not have sensing and thermoregulation ability [2]. ...
Article
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Skin substitutes are a restorative material used to treat many skin injuries by replacing or masking the wound. It is also capable of producing an original skin type. In this study, gold nanoparticle–aided skin substitutes were prepared using biodegradable materials (chitosan, sodium alginate, and gelatin) under the magnetic stirring method. Gold ions were reduced using aqueous extract of Cyperus rotundus and Hemigraphis alternata. The formation of prepared gold nanoparticles was confirmed using spectroscopy techniques. The physical parameters of the skin substitutes were tested, and it was characterized using FTIR, DTG, laser profilometer, and FESEM analysis. HAaNP-aided skin substitutes have a bubble-like texture, and it facilitates higher water-absorbing ability. CRaNP aided skin substitutes reducing the hydrophilicity of the prepared skin substitutes. Antioxidant and antifungal skin substitute activities were carried out using DPPH radical scavenging activity and disk diffusion method, respectively. The antioxidant activity revealed the skin substitutes to possess significant free radical inhibition and as the number of gold nanoparticles increases, the activity also increases. The prepared samples show excellent activity against Aspergillus niger. The MTT assay reveals that the cancer cell (A-375) viability decreases by increasing skin substitutes’ concentration. The normal cells (HEK-293) were cultured in a medium containing skin substitutes, facilitating the growth of cells. The cell attachment was observed in prepared cell lines after 24-h treatment. The results of this study suggest the prepared Cyperus rotundus and Hemigraphis alternata embedded with gold nanoparticle–aided skin substitutes are a promising material for medical and cosmetic application.
... The first category includes mechanical parameters such as temperature, pressure, strain, and acceleration [39,40]. Mechanical parameters have been used in voice recognition [41,42], artificial tactile [43][44][45], and pulsation tattoo sensors [22] so far. The physical mechanisms of mechanical tattoo sensors have also been classified as piezoresistive, capacitive, ionotronics, and piezoelectricity subcategories [46]. ...
Article
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Previous research results should be compared and classified to offer satisfactory solutions to challenges facing the ideation and development of stretchable biosensors. At the same time, human body protein detection is of great importance because of being the most significant biomarker in patient health monitoring. Therefore, a literature review was conducted on flexible electronics to cover target biomarkers, measurement mechanism of affinity flexible biosensors, sensor fabrication materials, sensor fabrication procedures, and environmental effects on sensor performance. The challenges facing the development of wearable tattoo biosensors were also identified. According to the results, affinity flexible biosensors can perform wearable health monitoring of chronic patients in the near future; however, there is a wide research gap between affinity and stretchable biosensors.
... This mechanical mismatch results in discomfort to users as well as considerable noise signals during data collection. Recent advances in soft functional materials and assembly techniques have led to the development of mechanically stretchable and flexible biosensors that can be unobtrusively integrated into the human skin in a manner that complies with the natural motion of the wearer [2,3]. The thin and flexible nature of these biosensors allows their conformal, seamless contact to the skin while simultaneously providing (i) excellent breathability and deformability for user comfort and (ii) durability to allow repeated attachment and detachment to the skin without irritating the wearer and damaging the devices. ...
Chapter
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Recent technological advances of soft functional materials and their assembly into wearable (i.e., on-skin) biosensors lead to the development of ground-breaking biomedical applications ranging from wearable health monitoring to drug delivery and to human-robot interactions. These wearable biosensors are capable of unobtrusively interfacing with the human skin and enabling long-term reliable monitoring of clinically useful biosignals associated with health and other conditions affecting well-being. Scalable assembly of diverse wearable biosensors has been realized through the elaborate combination of intrinsically stretchable materials including organic polymers or/and low-dimensional inorganic nanomaterials. In this Chapter, we review various types of wearable biosensors within the context of human health monitoring with a focus of their constituent materials, mechanics designs, and large-scale assembly strategies. In addition, we discuss the current challenges and potential future research directions at the end of this chapter.
... Combined tactile feedback with a computer via a touch screen and its functionality for prosthetic hands have been demonstrated. Thereafter, numerous applications of tactile sensors and e-skins have been identified in robotics, artificial intelligence, prosthetics, health monitoring technologies and human-machine interfaces, making e-skin one of the trending research topics [6][7][8][9][10]. For example, e-skins can be used to provide action related information (e.g. ...
Article
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Electronic skin (e-skin) is an artificial skin that mimics the sensing capabilities of human skin, which brings many potential applications in robotics, artificial intelligence, prosthetics, and health monitoring technologies. Many attempts associated with various mechanisms/approaches and materials/structures have been developed to match the e-skins to the particular functions of specific applications. Along the time, high sensitivity, mechanical flexibility/stretchability, multifunction, and large area are common driving forces in the research area. New materials, with a variety of structures and unique properties, offer a plenty of freedoms in designing and fabricating e-skins. Significant progress has been made in recently years. This paper firstly reviews the most recent progress on nanomaterial- based e-skins according to four major sensing mechanisms, with an emphasis on the effects of various materials on the sensitivity and stretchability of e-skins. Then the paper updates the progress and effort with respect to multifunctional e-skins and organic-thin-film-transistor based large-area e-skins. Further development possibilities are also briefly discussed.
Chapter
Skin is a complex tissue with a diverse range of mechanical properties that play essential roles in protecting the body, regulating temperature, sensing touch, pressure, and supporting various biological functions.
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Chapter
The skin can self-renew, thanks to the presence of stem cells in the hypodermisHypodermis. However, when the skin is damaged in the deeper layers, as in second or third-degree burnsBurns, the normal wound healingWound healing responses are impeded, resulting in a chronic injury.
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A high performance electronic hair (EH) sensor with multi-responsibility is fabricated via fully mimicking the sensory structure and properties of human skin. The EH sensor is designed to consist of nylon fibers as hairs for mechanical signal amplification and polydimethylsiloxane (PDMS) resin as human skin for sensor encapsulation. Two carbonized papers are used as piezo-resistive mechanoreceptors (M1 and M2). The nylon fibers used have a diameter and Young’s modulus close to those of hairs and PDMS has a Young’s modulus close to that of human skin. The structure of human hairs is verified to be optimal for maximum sensing ability and the structure of EH sensor is then optimized in terms of the structure of human hairs. Unlike conventional single-mode EH sensors, the EH sensor by fully mimicking human skin is capable of detecting multiple signals of pressure, surface roughness and airflow rate, etc. just like human skin. Moreover, the EH sensor is also effective to identify airflow direction. Because of its simple structure, low cost, good flexibility and multi-functionality, the EH sensor is expected to find widespread application in e-skins, wearable devices, robotics, and human machine interfaces, etc.
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Skin protects the body from exogenous substances and functions as a barrier to fluid loss and trauma. The skin comprises of epidermal, dermal and hypodermal layers, which mainly contain keratinocytes, fibroblasts and adipocytes, respectively, typically embedded on extracellular matrix made up of glycosaminoglycans and fibrous proteins. When the integrity of skin is compromised due to injury as in burns the coverage of skin has to be restored to facilitate repair and regeneration. Skin substitutes are preferred for wound coverage when the loss of skin is extensive especially in the case of second or third degree burns. Different kinds of skin substitutes with different features are commercially available; they can be classified into acellular skin substitutes, those with cultured epidermal cells and no dermal components, those with only dermal components, and tissue engineered substitutes that contain both epidermal and dermal components. Typically, adult wounds heal by fibrosis. Most organs are affected by fibrosis, with chronic fibrotic diseases estimated to be a leading cause of morbidity and mortality. In the skin, fibroproliferative disorders such as hypertrophic scars and keloid formation cause cosmetic and functional problems. Dermal fibroblasts are understood to be heterogeneous; this may have implications on post-burn wound healing since studies have shown that superficial and deep dermal fibroblasts are anti-fibrotic and pro-fibrotic, respectively. Selective use of superficial dermal fibroblasts rather than the conventional heterogeneous dermal fibroblasts may prove beneficial for post-burn wound healing.
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The skin is the largest organ of the human body and can sense pressure, temperature, and other complex environmental stimuli or conditions. The mimicry of human skin's sensory ability via electronics is a topic of innovative research that could find broad applications in robotics, artificial intelligence, and human–machine interfaces, all of which promote the development of electronic skin (e-skin). To imitate tactile sensing via e-skins, flexible and stretchable pressure sensor arrays are constructed based on different transduction mechanisms and structural designs. These arrays can map pressure with high resolution and rapid response beyond that of human perception. Multi-modal force sensing, temperature, and humidity detection, as well as self-healing abilities are also exploited for multi-functional e-skins. Other recent progress in this field includes the integration with high-density flexible circuits for signal processing, the combination with wireless technology for convenient sensing and energy/data transfer, and the development of self-powered e-skins. Future opportunities lie in the fabrication of highly intelligent e-skins that can sense and respond to variations in the external environment. The rapidly increasing innovations in this area will be important to the scientific community and to the future of human life.
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35.2 million annual cases in the U.S. require clinical intervention for major skin loss. To meet this demand, the field of skin tissue engineering has grown rapidly over the past 40 years. Traditionally, skin tissue engineering relies on the "cell-scaffold-signal" approach, whereby isolated cells are formulated into a three-dimensional substrate matrix, or scaffold, and exposed to the proper molecular, physical, and/or electrical signals to encourage growth and differentiation. However, clinically available bioengineered skin equivalents (BSEs) suffer from a number of drawbacks, including time required to generate autologous BSEs, poor allogeneic BSE survival, and physical limitations such as mass transfer issues. Additionally, different types of skin wounds require different BSE designs. MicroRNA has recently emerged as a new and exciting field of RNA interference that can overcome the barriers of BSE design. MicroRNA can regulate cellular behavior, change the bioactive milieu of the skin, and be delivered to skin tissue in a number of ways. While it is still in its infancy, the use of microRNAs in skin tissue engineering offers the opportunity to both enhance and expand a field for which there is still a vast unmet clinical need. Here we give a review of skin tissue engineering, focusing on the important cellular processes, bioactive mediators, and scaffolds. We further discuss potential microRNA targets for each individual component, and we conclude with possible future applications. Copyright © 2015. Published by Elsevier B.V.
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The piezopotential-powered active matrix strain sensor array based on piezopotential-gated graphene transistor (GT) is demonstrated using a piezoelectric polymer. The strain sensor based on piezopotential-gated GT exhibits excellent performances including ultrahigh sensitivity (gauge factor = 389) and good durability (>3000 bending and releasing cycles) with a minimum detectable strain at 0.008%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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The extracellular matrix (ECM) is a complex and dynamic three-dimensional (3D) environment consisting largely of a variety of collagenous and non-collagenous fibres, non-fibrous proteins and proteoglycans. Other components often overlooked include various growth factors and other signalling molecules which can diffuse through and bind to various components. The fibrous components of the ECM have a nanoscale architecture to which cells embedded in the ECM, and other biomolecules can attach. Many strategies are being explored to create ECM mimics for tissue engineering applications and as 3D cell-culture environments. These range from fibrous scaffolds composed of synthetic polymers or biopolymers, to fibrous and non-fibrous hydrogel systems. This review will focus on the field of self-assembled nanofibrous hydrogels as ECM mimics and their application to cell and tissue engineering.
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Sensory receptors in human skin transmit a wealth of tactile and thermal signals from external environments to the brain. Despite advances in our understanding of mechano- and thermosensation, replication of these unique sensory characteristics in artificial skin and prosthetics remains challenging. Recent efforts to develop smart prosthetics, which exploit rigid and/or semi-flexible pressure, strain and temperature sensors, provide promising routes for sensor-laden bionic systems, but with limited stretchability, detection range and spatio-temporal resolution. Here we demonstrate smart prosthetic skin instrumented with ultrathin, single crystalline silicon nanoribbon strain, pressure and temperature sensor arrays as well as associated humidity sensors, electroresistive heaters and stretchable multi-electrode arrays for nerve stimulation. This collection of stretchable sensors and actuators facilitate highly localized mechanical and thermal skin-like perception in response to external stimuli, thus providing unique opportunities for emerging classes of prostheses and peripheral nervous system interface technologies.
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This review gives a brief description on the skin and its essential functions, damages or injury which are common to the skin and the role of skin substitute to replace the functions of the skin soon after an injury. Skin substitutes have crucial role in the management of deep dermal and full thickness wounds. At present, there is no skin substitute in the market that can replace all the func-tions of skin 'and the research is still continuing for a better alternative. This review is an attempt to recollect and report the past efforts including skin grafting and recent trends like use of bioengineered smart skin substitutes in wound care. Incorporation functional moieties like antimicrobials and wound healing agents are also described.
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Background For patients with full thickness skin defects, autologous Split-thickness skin grafts (STSG) are generally regarded as the mainstay of treatment. However, skin grafts have some limitations, including undesirable outcomes resulting from scars, poor elasticity, and limitations in joint movement due to contractures. In this study, we present outcomes of Matriderm grafts used for various skin tissue defects whether it improves on these drawbacks. Methods From January 2010 to March 2012, a retrospective review of patients who had undergone autologous STSG with Matriderm was performed. We assessed graft survival to evaluate the effectiveness of Matriderm. We also evaluated skin quality using a Cutometer, Corneometer, Tewameter, or Mexameter, approximately 12 months after surgery. Results A total of 31 patients underwent STSG with Matriderm during the study period. The success rate of skin grafting was 96.7%. The elasticity value of the portion on which Matriderm was applied was 0.765 (range, 0.635-0.800), the value of the trans-epidermal water loss (TEWL) was 10.0 (range, 8.15-11.00) g/hr/m2, and the humidification value was 24.0 (range, 15.5-30.0). The levels of erythema and melanin were 352.0 arbitrary unit (AU) (range, 299.25-402.75 AU) and 211.0 AU (range, 158.25-297.00 AU), respectively. When comparing the values of elasticity and TEWL of the skin treated with Matriderm to the values of the surrounding skin, there was no statistically significant difference between the groups. Conclusions The results of this study demonstrate that a dermal substitute (Matriderm) with STSG was adopted stably and with minimal complications. Furthermore, comparing Matriderm grafted skin to normal skin using Cutometer, Matriderm proved valuable in restoring skin elasticity and the skin barrier.
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The aim of the study was an objective in vivo assessment of skin properties after reconstruction with two artificial dermal substitutes, Integra® and Hyalomatrix®. Twenty-seven patients underwent reconstruction of 36 skin-loss sites with full-thickness skin graft, split-thickness skin graft, Hyalomatrix® bioengineered skin substitute and sequential split-thickness skin graft and Integra® bioengineered skin substitute and sequential split-thickness skin graft. Objective assessments were carried out using three instrumental devices: Multi Probe Adapter System MPA; 22 MHz ultrasound skin scan; and Primos Pico for a three-dimensional (3D) skin scan. The skin parameters under study in our sample were: corneometry, transepidermal water loss, elastometry, colorimetry, skin thickness and 3D skin surface pattern. A skin reconstruction with Hyalomatrix seemed to most closely approach the hydration, transepidermal water loss and skin surface 3D pattern of normal skin. A skin reconstruction with Integra seemed to demonstrate the best skin colour feature and elastic properties. Although no statistically significant differences were observed, the descriptive analysis of the outcomes might suggest a better cell regulation, regenerated extracellular matrix and neoangiogenesis with the use of Hyalomatrix, and the formation of a more elastic regenerated dermis, with overall better physical, mechanical and optical properties, with the use of Integra. © 2014 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons Ltd.
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Electronic devices that mimic the properties of skin have potential important applications in advanced robotics, prosthetics, and health monitoring technologies. Methods for measuring tactile and temperature signals have progressed rapidly due to innovations in materials and processing methods. Imparting skin-like stretchability to electronic devices can be accomplished by patterning traditional electronic materials or developing new materials that are intrinsically stretchable. The incorporation of sensing methods with transistors facilitates large-area sensor arrays. While sensor arrays have surpassed the properties of human skin in terms of sensitivity, time response, and device density, many opportunities remain for future development.
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Recent restrictions on the testing of cosmetic ingredients in animals have resulted in the need to test the genotoxic potential of chemicals exclusively in vitro prior to licensing. However, as current in vitro tests produce some misleading positive results, sole reliance on such tests could prevent some chemicals with safe or beneficial exposure levels from being marketed. The 3D human reconstructed skin micronucleus (RSMN) assay is a promising new in vitro approach designed to assess genotoxicity of dermally applied compounds. The assay utilises a highly differentiated in vitro model of the human epidermis. For the first time, we have applied automated micronucleus detection to this assay using MetaSystems Metafer Slide Scanning Platform (Metafer), demonstrating concordance with manual scoring. The RSMN assay’s fixation protocol was found to be compatible with the Metafer, providing a considerably shorter alternative to the recommended Metafer protocol. Lowest observed genotoxic effect levels (LOGELs) were observed for mitomycin-C at 4.8 µg/ml and methyl methanesulfonate (MMS) at 1750 µg/ml when applied topically to the skin surface. In-medium dosing with MMS produced a LOGEL of 20 µg/ml, which was very similar to the topical LOGEL when considering the total mass of MMS added. Comparisons between 3D medium and 2D LOGELs resulted in a 7-fold difference in total mass of MMS applied to each system, suggesting a protective function of the 3D microarchitecture. Interestingly, hydrogen peroxide (H2O2), a positive clastogen in 2D systems, tested negative in this assay. A non-genotoxic carcinogen, methyl carbamate, produced negative results, as expected. We also demonstrated expression of the DNA repair protein N-methylpurine-DNA glycosylase in EpiDerm™. Our preliminary validation here demonstrates that the RSMN assay may be a valuable follow-up to the current in vitro test battery, and together with its automation, could contribute to minimising unnecessary in vivo tests by reducing in vitro misleading positives.
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A wide variety of tactile (touch) sensors exist today for robotics and related applications. They make use of various transduction methods, smart materials and engineered structures, complex electronics, and sophisticated data processing. While highly useful in themselves, effective utilization of tactile sensors in robotics applications has been slow to come and largely remains elusive today. This paper surveys the state of the art and the research issues in this area, with the emphasis on effective utilization of tactile sensors in robotic systems. One specific with the use of tactile sensing in robotics is that the sensors have to be spread along the robot body, the way the human skin is-thus dictating varied 3-D spatio-temporal requirements, decentralized and distributed control, and handling of multiple simultaneous tactile contacts. Satisfying these requirements pose challenges to making tactile sensor modality a reality. Overcoming these challenges requires dealing with issues such as sensors placement, electronic/mechanical hardware, methods to access and acquire signals, automatic calibration techniques, and algorithms to process and interpret sensing data in real time. We survey this field from a system perspective, recognizing the fact that the system performance tends to depend on how its various components are put together. It is hoped that the survey will be of use to practitioners designing tactile sensing hardware (whole-body or large-patch sensor coverage), and to researchers working on cognitive robotics involving tactile sensing.
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Diverse signals generated from the sensing elements embedded in flexible electronic skins (e-skins) are typically interfered by strain energy generated through processes such as touching, bending, stretching or twisting. Herein, we demonstrate a flexible bimodal sensor that can separate a target signal from the signal by mechanical strain through the integration of a multi-stimuli responsive gate dielectric and semiconductor channel into the single field-effect transistor (FET) platform.
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Scientists are exploring elastic and soft forms of robots, electronic skin and energy harvesters, dreaming to mimic nature and to enable novel applications in wide fields, from consumer and mobile appliances to biomedical systems, sports and healthcare. All conceivable classes of materials with a wide range of mechanical, physical and chemical properties are employed, from liquids and gels to organic and inorganic solids. Functionalities never seen before are achieved. In this review we discuss soft robots which allow actuation with several degrees of freedom. We show that different actuation mechanisms lead to similar actuators, capable of complex and smooth movements in 3d space. We introduce latest research examples in sensor skin development and discuss ultraflexible electronic circuits, light emitting diodes and solar cells as examples. Additional functionalities of sensor skin, such as visual sensors inspired by animal eyes, camouflage, self-cleaning and healing and on-skin energy storage and generation are briefly reviewed. Finally, we discuss a paradigm change in energy harvesting, away from hard energy generators to soft ones based on dielectric elastomers. Such systems are shown to work with high energy of conversion, making them potentially interesting for harvesting mechanical energy from human gait, winds and ocean waves.
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According to the current European legislation, the safety assessment of each individual cosmetic ingredient of any formulation is the basis for the safety evaluation of a cosmetic product. Also, animal testing in the European Union is prohibited for cosmetic ingredients and products since 2004 and 2009, respectively. Additionally, the commercialization of any cosmetic products containing ingredients tested on animal models was forbidden in 2009. In consequence of these boundaries, the European Centre for the Validation of Alternative Methods (ECVAM) proposes a list of validated cell-based in vitro models for predicting the safety and toxicity of cosmetic ingredients. These models have been demonstrated as valuable and effective tools to overcome the limitations of animal in vivo studies. Although the use of in vitro cell-based models for the evaluation of absorption and permeability of cosmetic ingredients is widespread, a detailed study on the properties of these platforms and the in vitro-in vivo correlation compared with human data are required. Moreover, additional efforts must be taken to develop in vitro models to predict carcinogenicity, repeat dose toxicity and reproductive toxicity, for which no alternative in vitro methods are currently available. This review paper summarizes and characterizes the most relevant in vitro models validated by ECVAM employed to predict the safety and toxicology of cosmetic ingredients.
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Cosmetics Europe recently established HPLC/UPLC-spectrophotometry as a suitable alternative endpoint detection system for measurement of formazan in the MTT-reduction assay of Reconstructed Human Tissue test methods irrespective of the test system involved. This addressed a known limitation for such test methods that use optical density for measurement of formazan and may be incompatible for evaluation of strong MTT reducer and/or coloured chemicals. To build on the original project, Cosmetics Europe has undertaken a second study that focuses on evaluation of chemicals with functionalities relevant to cosmetic products. Such chemicals were primarily identified from the Scientific Committee on Consumer Safety (SCCS) 2010 memorandum (addendum) on the in vitro test EpiSkin™ for skin irritation testing. Fifty test items were evaluated in which both standard photometry and HPLC/UPLC-spectrophotometry were used for endpoint detection. The results obtained in this study: 1) provide further support for Within Laboratory Reproducibility of HPLC-UPLC-spectrophotometry for measurement of formazan; 2) demonstrate, through use a case study with Basazol C Blue pr. 8056, that HPLC/UPLC-spectrophotometry enables determination of an in vitro classification even when this is not possible using standard photometry and 3) addresses the question raised by SCCS in their 2010 memorandum (addendum) to consider an endpoint detection system not involving optical density quantification in in vitro Reconstructed Human Epidermis skin irritation test methods.
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In vivo friction and indentation deformation experiments were carried out using the human volar forearm of a healthy 29 year old Caucasian woman and compared with various synthetic materials in order to select materials and develop a new moisture-sensitive artificial skin model (ASM). Analogous to human skin the final ASM comprised two different layers: a relatively stiff hydrophilic moisture-absorbing top layer representing the epidermis and a very soft under-layer representing the dermis and hypodermis. The friction and deformation behaviour of the new ASM was comparable to human skin when tested under dry and moist skin conditions. This development has potential for use as a test-bed in the development of devices that interact with the skin in a mechanical way.
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Nanomaterials serve as promising candidates for strain sensing due to unique electromechanical properties by appropriately assembling and tailoring their configurations. Through the crisscross interlacing of graphene micro-ribbons in an over-and-under fashion, the obtained graphene woven fabric (GWF) indicates a good trade-off between the sensitivity and stretchability compared with those in previous studies. In this work, the function of woven fabrics for highly sensitive strain sensing is investigated although network configuration is always a strategy to retain resistance stability. The experimental and simulation results indicate that the ultrahigh mechano-sensitivity with gauge factors of 500 under 2% strain is attributed to the macro woven-fabric geometrical conformation of graphene which induces a large interfacial resistance between the interlaced ribbons and a formation of microscale controllable, locally oriented zigzag cracks near the crossover location, both of which have synergistic effect on improving sensitivity. Meanwhile, the stretchability of GWF could be tailored to as high as over 40% strain by adjusting graphene growth parameters and adopting oblique angle direction stretching simultaneously. We also demonstrate that sensors based on GWFs are applicable to human motion detection, sound signal acquisition and spatially resolved monitoring of external stress distribution.
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The microelectronics technology and subsequent miniaturization that began almost immediately after the transistor was invented have improved our lives through revolutionized computing and communication. The exponential rate of advancement that is described in Moore's Law has been propelled by $1Tr of investment over 50 years. Recent advances in the field pursued through 'More than Moore' technology and propelled by applications such as wearable electronics and bendable displays. These applications require realizing electronics on unconventional substrates such as plastics. The possibility to realize sensitive electronics systems on large areas is another aspect of this burgeoning field, which will open new application avenues such as intelligent robotics enabled by conformable electronic skin wrapped around the body of a robot or artificial limbs. In this paper, I will summarize the results presented in the invited lecture on the development of flexible electronics in context with realizing electronics skin. Starting with the development of electronic skin using off-the-shelf sensors and electronic components on flexible printed circuit boards (PCB) and followed by various electronic skin approaches, the lecture concluded with a discussion on emerging novel approaches involving printed silicon nanowires.
Article
Artificial electronic skin consists of mechanically flexible and stretchable sensor networks that can accommodate irregular surfaces and spatially map/quantify various stimuli, such as strains, pressures, and temperatures to imitate the human somatosensory system. Here, a flexible/wearable multifunctional sensor array is designed and fabricated in a cost-effective manner through simple fabrication procedures for highly-sensitive contact/pressure/strain detections. Composed of PET-based Ag serpentine-shaped electrodes, the sensor array is implemented for static and dynamic mapping of spatial contact/pressure/strain distributions in large-scale, with a detection limit of 6 Pa (corresponding to 0.5 mg). By attaching the flexible/wearable devices on human body, different motions are recognized/distinguished for gesture control applications. Combining the easy-fabricated and low-cost features, these sensor arrays may become promising candidate for highly-sensitive force detections, gesture controls, imaging of spatial pressure distributions, and find potential applications in advanced robotics, human-machine interfaces, next-generation prosthetics and healthcare monitoring devices.
Article
Engineered skin substitutes are widely used in skin wound management. However, no currently available products satisfy all the criteria of usability in emergency situations, easy handling, and minimal scar formation. To overcome these shortcomings, we designed a cell-free bandage-type artificial skin, named "VitriBand", using adhesive film dressing, silicone-coated polyethylene terephthalate film, and collagen xerogel membrane defined as a dried collagen vitrigel membrane without free water. We analyzed its advantages over in-line products by comparing VitriBand with hydrocolloid dressing and collagen sponge. For evaluation, mice inflicted with full-thickness skin defects were treated with VitriBand, hydrocolloid dressing, and collagen sponge. A plastic film group treated only with adhesive film dressing and silicone-coated polyethylene terephthalate film, and a no treatment group were also compared. VitriBand promoted epithelization while inhibiting the emergence of myofibroblasts and inflammation in the regenerating tissue more effectively than the plastic film, hydrocolloid dressing, and collagen sponge products. We have succeeded in establishing a cell-free bandage-type artificial skin that could serve as a promising first-line medical biomaterial for emergency treatment of skin injuries in various medical situations. This article is protected by copyright. All rights reserved. © 2015 by the Wound Healing Society.
Article
Biological systems are subjected to moderate-to-high strain rates in blast-type traumatic injuries. An improved understanding of the responses of cells and tissues to extreme mechanical stresses could improve mitigation and post-injury treatment strategies. A key aim of this research is to create biologically meaningful injury models of soft tissues. Here the authors examine the material and cellular properties of freshly harvested porcine skin in compression. The data presented suggest that fresh skin differentially responds low to moderate strain rates as a composite rather than that of a homogeneous polymer. The implications of this work are discussed in terms of creating improved analytical models to describe the material properties of fresh skin.
Article
Due to its very peculiar features, the development of e-skin can be effectively tackled using a holistic approach. Starting from the definition of system specifications, the mechanical arrangement of the skin itself needs to be designed and fabricated together with the electronic embedded system, to move towards aspects such as tactile data processing algorithms and the communication channel interface.In this paper we present the design, the implementation and the results on the way of the development of an electronic skin (e-skin) system based on arrays of piezopolymer transducers. Focus of the paper is on both the development of innovative approaches for tactile information processing and electronic system embedding into the e-skin structure. In particular, Machine Learning technologies can provide a powerful tool to tackle the pattern-recognition problems involved in the tactile sensing framework and the ability of processing data represented as N-th order tensor is the key aspect of the presented research, which can be seen as an application of an existing method (Signoretto et al., 2011). The experimental session compares two different implementations of the ML-based framework, which differ in the learning paradigm adopted, namely SVM and ELM (K-ELM). The effectiveness of the adopted pattern-recognition technologies in the classification of touch modalities has been confirmed by addressing two different binary classification problems in an experiment involving 70 participants. The computational requirements for the hardware implementation of the proposed algorithm together with an overview of what exists in the existing literature are finally discussed.
Article
In recent years there has been a drive to create experimental techniques that can facilitate the accurate and precise prediction of transdermal permeation without the use of in vivo studies. This review considers why permeation data is essential, provides a brief summary as to how skin acts as a natural barrier to permeation and discusses why in vivo studies are undesirable. This is followed by an in-depth discussion on the extensive range of alternative methods that have been developed in recent years. All of the major 'skin mimic systems' are considered including: in vitro models using synthetic membranes, mathematical models including quantitative structure-permeability relationships (QSPRs), human skin equivalents and chromatographic based methods. All of these model based systems are ideally trying to achieve the same end-point, namely a reliable in vitro-in vivo correlation, i.e. matching non-in vivo obtained data with that from human clinical trials. It is only by achieving this aim, that any new method of obtaining permeation data can be acknowledged as a potential replacement for animal studies, for the determination of transdermal permeation. In this review the relevance, and potential applicability, of the various model systems will also be discussed.
Article
The development of electronic skin (e-skin) is of great importance in human-like robotics, healthcare, wearable electronics, and medical applications. In this paper, a bioinspired e-skin design of hierarchical micro- and nano-structured ZnO nanowire (NW) arrays in an interlocked geometry is suggested for the sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. The interlocked hierarchical structures enable a stress-sensitive variation in the contact area between the interlocked ZnO NWs and also the efficient bending of ZnO NWs, which allow the sensitive detection of both static and dynamic tactile stimuli. The flexible e-skin in a piezoresistive mode shows a high pressure sensitivity (−6.8 kPa−1) and an ultrafast response time (<5 ms), which enables the detection of minute static pressure (0.6 Pa), vibration level (0.1 m s−2), and sound pressure (≈57 dB). The flexible e-skin in a piezoelectric mode is also demonstrated to be able to detect fast dynamic stimuli such as high frequency vibrations (≈250 Hz). The flexible e-skins with both piezoresistive and piezoelectric sensing capabilities may find applications requiring both static and dynamic tactile perceptions such as robotic hands for dexterous manipulations and various healthcare monitoring devices.
Article
The usefulness of the synthetic membrane, Strat-M™ as an alternative to human and animal skins was evaluated by estimating the skin permeabilities of chemical compounds. Thirteen chemical compounds with molecular weights (M.W.) of 152-289 and lipophilicities (log Ko/w) of -0.9 to 3.5 were selected. Strat-M™, excised human skin, or hairless rat skin was set in a Franz-type diffusion cell and a saturated solution of each chemical compound was applied to determine membrane permeation profiles. The obtained permeability coefficients (log P) were compared among these membranes. Elevations were observed in log P for Strat-M™ with an increase in the log Ko/w of the applied compounds, and similar results were observed with the human and hairless rat skins. A correlation was obtained in log P values between Strat-M™ and human or hairless rat skin. Furthermore, the diffusion and partition parameters of chemicals in Strat-M™ were similar to those in the excised human and rat skins. These results suggest that Strat-M™ could be used as an alternative to animal or human skin in permeation studies. Copyright © 2014. Published by Elsevier B.V.
Article
Pressure sensors based on solution-processed metal-organic frameworks nanowire arrays are fabricated with very low cost, flexibility, high sensitivity, and ease of integration into sensor arrays. Furthermore, the pressure sensors are suitable for monitoring and diagnosing biomedical signals such as radial artery pressure waveforms in real time. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Article
(Trans)dermal drug therapy is gaining increasing importance in the modern drug development. To fully utilize the potential of this route, it is important to optimize the delivery of active ingredient/drug into/through the skin. The optimal carrier/vehicle can enhance the desired outcome of the therapy therefore the optimization of skin formulations is often included in the early stages of the product development. A rational approach in designing and optimizing skin formulations requires well-defined skin models, able to identify and evaluate the intrinsic properties of the formulation. Most of the current optimization relies on the use of suitable ex vivo animal/human models. However, increasing restrictions in use and handling of animals and human skin stimulated the search for suitable artificial skin models. This review attempts to provide an unbiased overview of the most commonly used models, with emphasis on their limitations and advantages. The choice of the most applicable in vitro model for the particular purpose should be based on the interplay between the availability, easiness of the use, cost and the respective limitations. Copyright © 2015. Published by Elsevier B.V.
Article
This report demonstrates a wearable elastomer-based electronic skin including resistive sensors for monitoring finger articulation and capacitive tactile pressure sensors that register distributed pressure along the entire length of the finger. Pressure sensitivity in the order of 0.001 to 0.01 kPa−1 for pressures from 5 to 405 kPa, which includes much of the range of human physiological sensing, is achieved by implementing soft, compressible silicone foam as the dielectric and stretchable thin-metal films. Integrating these sensors in a textile glove allows the decoupling of the strain and pressure cross-sensitivity of the tactile sensors, enabling precise grasp analysis. The sensorized glove is implemented in a human-in-the-loop system for controlling the grasp of objects, a critical step toward hand prosthesis with integrated sensing capabilities.
Conference Paper
This paper presents all screen printed flexible pressure sensors arrays with Polyvinylidene Fluoride-Trifluoroethylene P(VDF-TrFE) sandwiched between patterned metal layers. Whilst bottom electrodes and P(VDF-TrFE) are printed on a 25 μm thick polyamide (PI) substrate, the top electrodes with force concentrator posts on backside are printed on a separate polyethylene terephthalate (PET) substrate and the two are then adhered with good alignment. Each sensor module consists of 4×4 sensors array, with each sensor having 1×1 mm2 sensitive area, and interconnection lines for expandability of the cells. Capacitance-voltage analysis at varying frequency and piezoelectric response of the sensor is presented. Whole package of foldable pressure sensor realized is completely developed by screen printing technology and is targeted towards realizing low-cost electronic skin. The sensors arrays have also been compared with similar sensors structures that were realized with spin coating.
Article
Stretchable electronic skins with multidirectional force-sensing capabilities are of great importance in robotics, prosthetics, and rehabilitation devices. Inspired by the interlocked microstructures found in epidermal-dermal ridges in human skin, piezoresistive interlocked microdome arrays are employed for stress-direction-sensitive, stretchable electronic skins. Here we show that these arrays possess highly sensitive detection capability of various mechanical stimuli including normal, shear, stretch, bending, and twisting forces. Furthermore, the unique geometry of interlocked microdome arrays enables the differentiation of various mechanical stimuli because the arrays exhibit different levels of deformation depending on the direction of applied forces, thus providing different sensory output patterns. In addition, we show that the electronic skins attached on human skin in the arm and wrist areas are able to distinguish various mechanical stimuli applied in different directions and can selectively monitor different intensities and directions of air flows and vibrations.
Article
Background Skin grafts with an artificial dermis have been widely used as a part of the efforts to minimize contractures and reduce donor-site scars. We conducted a prospective randomized clinical trial to study the effect of a dermal substitute by measuring the size of the graft after surgery for months. Method The artificial dermis (Matriderm, Dr. Suwelack Skin and Health Care AG, Billerbeck, Germany) was applied in combination with a split-thickness autograft in 40 patients with acute burn wounds or scar reconstruction. Demographic and medical data were collected on each patient. We directly measured the graft size by using a transparent two-ply film (Visitrak Grid, Smith & Nephew Wound Management, Inc, Largo, FL, USA) intraoperatively and 1, 2, 3, and 6 months postoperatively. For effective data comparison, the size of the graft at the time of surgery was taken to be “100%.” Then, the size in each phase was estimated in percentage (%). Result During the 1st month, the average size was 89%. The figure decreased to 86% and 82% in the 2nd and 3rd months, respectively. In the 6th month, it slightly rebounded to 85% but failed to return to the original state. The size of patients with acute burns was smaller than the size of scar patients as follows: 85–91% in the 2nd month, 81–87% in the 3rd month, and 85–96% in the 6th month. Conclusion This study examined the progress of skin grafts through the measurement of graft size in the human body. The grafted skin underwent contracture and remodeling for 3–6 months. In terms of skin contraction, an acute burn was more serious than scar reconstruction. The use of an artificial dermis that contains elastin is very effective from the functional and esthetic perspective by minimizing contractures and enhancing skin elasticity.
Article
The first stretchable energy harvesting e-skin (EHES) that is able to detect, differentiate, and harvest a variety of mechanical stimuli, enabled by the stretchability of the device and a unique device architecture was reported. Using PDMS microstructuring in combination with an air gap, the researchers enabled pressure sensing from several pascals to tens of kilopascals. The device was capable of differentiating different tactile signals by measuring three different output signals (capacitance, resistance of the top and resistance of the bottom electrode). The capacitive design was important since the top and the bottom electrodes needed to be electrically isolated so that the measured change in film resistance was only due to the lateral straining of each film, not due to the electrical conduction between the top and bottom electrodes. Capacitive sensor design also enabled energy-harvesting functionality along with its sensing capability. envision that our energy-harvesting e-skin and the concepts introduced here can be utilized in the future to enable a fully self-sustainable skin-like devices with stretchability, multifunctional tactile sensing, and energy-harvesting capability.
Article
Articular cartilage has poor ability to heal once damaged. Tissue engineering with scaffolds of polymer hydrogels is promising for cartilage regeneration and repair. Polymer hydrogels composed of highly hydrated crosslinked networks mimic the collagen networks of the cartilage extracellular matrix and thus are employed as inserts at cartilage defects not only to temporarily relieve the pain but also to support chondrocyte proliferation and neocartilage regeneration. The biocompatibility, biofunctionality, mechanical properties, and degradation of the polymer hydrogels are the most important parameters for hydrogel-based cartilage tissue engineering. Degradable biopolymers with natural origin have been widely used as biomaterials for tissue engineering because of their outstanding biocompatibility, low immunological response, low cytotoxicity, and excellent capability to promote cell adhesion, proliferation, and regeneration of new tissues. This review covers several important natural proteins (collagen, gelatin, fibroin, and fibrin) and polysaccharides (chitosan, hyaluronan, alginate and agarose) widely used as hydrogels for articular cartilage tissue engineering. The mechanical properties, structures, modification, and structure–performance relationship of these hydrogels are discussed since the chemical structures and physical properties dictate the in vivo performance and applications of polymer hydrogels for articular cartilage regeneration and repair. © 2012 Society of Chemical Industry
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Hidradenitis suppurativa is a chronic and often refractory skin disease that can require radical excision of the full layer of fatty tissue under the lesion. Closure using a split-thickness skin graft often results in depression deformity and lack of tissue flexibility. We have developed a two-stage procedure to preserve fatty tissue during radical excision and apply an artificial dermis graft, and we have performed this procedure in 18 patients (33 lesions). To describe our two-stage procedure and report results of the procedure in our patient series. In the first step, all diseased skin including the superficial subcutaneous fatty tissue is excised; normal deep subcutaneous fatty tissue is preserved. Artificial dermis is then grafted to the preserved fatty tissue. Two weeks later, split-thickness skin grafts are applied to the skin defects. We evaluated graft success, any recurrence, and postoperative appearance in our patients, who were followed up for 8 to 36 months. All 32 skin grafts were successful. There was only one recurrence, which was treated using reoperation, and postoperative appearances were good. Our new procedure incorporating artificial dermis appears to be a good treatment option for advanced hidradenitis suppurativa.