Asa H Barber

Asa H Barber
London South Bank University | LSBU · School of Engineering

Professor

About

103
Publications
30,220
Reads
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5,224
Citations
Citations since 2017
19 Research Items
2345 Citations
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20172018201920202021202220230100200300400
Introduction
Asa H Barber currently works at the School of Engineering, University of Portsmouth. Asa does research in Materials Engineering, Mechanical Engineering and Bioengineering.
Additional affiliations
January 2018 - present
London South Bank University
Position
  • Head of Faculty
Description
  • Prof. Barber’s interests are in materials engineering and particularly the mechanical behaviour of composite-like structures. Many research activities have focussed on constituents with reduced dimensions, such as polymeric nanofibers, carbon nanotubes and graphene, and the building blocks used to assemble biological structures. Such research has often required the development of novel mechanical and imaging techniques. These interests have a broad range of applications.
December 2014 - December 2017
University of Portsmouth
Position
  • Professor
February 2006 - September 2014
Queen Mary, University of London
Position
  • Lecturer
Education
September 1997 - January 2001
Imperial College London
Field of study
  • Mechanics of composites

Publications

Publications (103)
Article
Full-text available
Many new engineering and scientific innovations have been proposed to date to passivate the novel coronavirus (SARS CoV-2), with the aim of curing the related disease that is now recognised as COVID-19. Currently, vaccine development remains the most reliable solution available. Efforts to provide solutions as alternatives to vaccinations are growi...
Article
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The biomaterial with the highest known tensile strength is a unique composite of chitin and goethite (α-FeO(OH)) present in teeth from the Common Limpet (Patella vulgata). A biomimetic based on limpet tooth, with corresponding high-performance mechanical properties is highly desirable. Here we report on the replication of limpet tooth developmental...
Article
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Additive Manufacturing (AM) often produces complex engineered structures by precisely distributing materials in a layer-by-layer fashion. Multimaterial AM is a particularly flexible technique able to combine a range of hard and soft materials to produce designed composites. Critically, the design of AM multimaterial structures requires the developm...
Article
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The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avo...
Article
Osteoregenerative biomaterials for the treatment of bone defects are under much development, with the aim of favouring osteointegration up to complete bone regeneration. A detailed investigation of bone-biomaterial integration is vital to understanding and predicting the ability of such materials to promote bone formation, preventing further bone d...
Article
Digital volume correlation (DVC), combined with in situ synchrotron microcomputed tomography (SR-microCT) mechanics, allows for 3D full-field strain measurement in bone at the tissue level. However, long exposures to SR radiation are known to induce bone damage, and reliable experimental protocols able to preserve tissue properties are still lackin...
Article
Full-text available
Teeth are complex biological structures consisting primarily of enamel and dentin. The mechanical loading of teeth due to the action of brushing provides a complex interaction between applied forces and the biological structure, resulting in volume loss of dental tissue. The volume loss as a resulting of using an ex situ brushing of teeth was measu...
Article
The use of synchrotron radiation micro-computed tomography (SR-microCT) is becoming increasingly popular for studying the relationship between microstructure and bone mechanics subjected to in situ mechanical testing. However, it is well known that the effect of SR X-ray radiation can considerably alter the mechanical properties of bone tissue. Dig...
Article
en A micromechanical characterization of biomaterials for bone tissue engineering is essential to understand the quality of the newly regenerated bone, enabling the improvement of tissue regeneration strategies. A combination of microcomputed tomography in conjunction with in situ mechanical testing and digital volume correlation (DVC) has become a...
Article
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Artificial teeth have several advantages in preclinical training. The aim of this study is to three‐dimensionally (3D) print accurate artificial teeth using scans from X‐ray microtomography (XMT). Extracted and artificial teeth were imaged at 90 kV and 40 kV, respectively, to create detailed high contrast scans. The dataset was visualised to produc...
Article
Objective: Hydration in denture adhesives regulates the formation of complex morphologies and mechanical function. Multiscale experimental approaches are required to evaluate the impact of hydration on the inherent heterogeneity of denture adhesive-based hydrogels at different length scales and the impact of such phenomena on adhesion performance....
Article
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Defect-free graphene nanosheets are the strongest material known but manufactured graphene tends to contain flaws of different forms and dimensions, leading to the degradation of mechanical performance. Here we report a quantitative mechanical approach to quantitatively evaluate the influence of defects within exfoliated pristine graphene sheets. R...
Article
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Understanding the penetration of liquids within textile fibers is critical for the development of next-generation smart textiles. Despite substantial research on liquid penetration in the plane of textile, little is known about how the liquid penetrates in the thickness direction. Here we report a time-resolved high-resolution X-ray measurement of...
Article
Electrospun nanofibers have ability to boost cell proliferation in tissue engineered scaffolds as their structure remind cells extra cellular matrix of the native tissue. The complex architecture and network of nanofibrous scaffolds requires advanced characterization methods to understand interrelationship between cells and nanofibers. In our study...
Article
Polystyrene (PS) commonly exhibits brittle behavior and poor mechanical properties due to the presence of structural heterogeneities promoting localized failure. The removal of this localized failure is shown here by processing PS into fibers with a range of diameters using electrospinning. Mechanical properties of individual electrospun fibers wer...
Article
Electrospinning is an increasingly common technique used to produce fibers with a range of diameters. These electrospun fibers are used extensively in applications that exploit the material’s high surface area to volume ratio, thus requiring detailed knowledge of the surface properties of the fibers. The surface free energy of individual free stand...
Article
Full-text available
Statement of significance: The tendon-to-bone attachment (enthesis) is a complex hierarchical tissue with features at a numerous scales that dissipate stress concentrations between compliant tendon and stiff bone. At the micrometer scale, the enthesis exhibits gradients in collagen and mineral composition and organization. However, the physiologic...
Chapter
Full-text available
The use of electrospun nanofibers for guided bone regeneration or bone scaffolds are becoming increasingly important in tissue engineering for next-generation healthcare. However, understanding the interaction between the nanofiber scaffolds that organize into complex 3D organizations and cells for optimized growth is a recurrent problem yet to be...
Article
Cortical bone is an example of a mineralized tissue containing a compositional distribution of hard and soft phases in 3-dimensional space for mechanical function. X-ray computed tomography (XCT) is able to describe this compositional and morphological complexity but methods to provide a physical output with comparable mechanical function is lackin...
Article
Objective: The mechanical properties of bio adhesives in oral care application are expected to be critical in defining the stability and release of devices such as dentures from the oral tissue. A multiscale experimental mechanical approach is used to evaluate the performance of denture adhesive materials. Methods: The inherent mechanical behavi...
Article
Full-text available
A matrix-fibril shear stress transfer approach is devised and developed in this paper to analyse the primary biomechanical factors which initiate the structural degeneration of the bioprosthetic heart valves (BHVs). Using this approach, the critical length of the collagen fibrils l c and the interface shear acting on the fibrils in both BHV and nat...
Article
The transmission of mechanical forces to the nucleus is important for intracellular positioning, mitosis, and cell motility, yet the contribution of specific components of the cytoskeleton to nuclear mechanotransduction remains unclear. In this study, we examine how cross-talk between the cytolinker plectin and F-actin controls keratin network orga...
Article
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This data article contains data related to the research article entitled “3D imaging of cell interactions with electrospun PLGA nanofiber membranes for bone regeneration” by Stachewicz et al. [1]. In this paper we include additional data showing degradation analysis of poly(d,l-lactide-co-glycolide acid) (PLGA) electrospun fibers in medium and air...
Article
Type VI collagen is a non-fibrillar collagen expressed in many connective tissues and implicated in extracellular matrix (ECM) organisation. We hypothesized that type VI collagen regulates matrix assembly and cell function within the dermis of the skin. In the present study we examined the expression pattern of type VI collagen in normal and wounde...
Article
Unlabelled: The interaction between resident cells and electrospun nanofibers is critical in determining resultant osteoblast proliferation and activity in orthopedic tissue scaffolds. The use of techniques to evaluate cell-nanofiber interactions is critical in understanding scaffold function, with visualization promising unparalleled access to sp...
Article
Wetting behavior between electrospun nanofibrous networks and liquids is of critical importance in many applications including filtration and liquid repellent textiles. The relationship between intrinsic nanofiber properties, including surface characteristics, and extrinsic nanofibrous network organization on resultant wetting characteristics of th...
Article
Full-text available
The teeth of limpets exploit distinctive composite nanostructures consisting of high volume fractions of reinforcing goethite nanofibres within a softer protein phase to provide mechanical integrity when rasping over rock surfaces during feeding. The tensile strength of discrete volumes of limpet tooth material measured using in situ atomic force m...
Article
The lamellar unit is a critical component in defining the overall mechanical properties of bone. In this paper, micro-beams of bone with dimensions comparable to the lamellar unit were fabricated using focused ion beam (FIB) microscopy and mechanically tested in bending to failure using atomic force microscopy (AFM). A variation in the mechanical p...
Article
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Osteoporosis is a disease known to promote bone fragility but the effect on the mechanical properties of bone material, which is independent of geometric effects, is particularly unclear. To address this problem, micro-beams of osteoporotic bone were prepared using focused ion beam microscopy and mechanically tested in compression using an atomic f...
Article
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The mechanical properties of graphene oxide (GO) paper are critically defined both by the mechanical properties of the constituent GO sheets and the interaction between these sheets. Functional carbonyl and carboxyl groups decorating defects, expected to be predominantly sheet edges of the GO, are shown to transfer forces to the in-plane carbon-car...
Article
The mechanical properties of electrospun fiber networks are critical in a range of applications from filtration to tissue engineering and are dependent on the adhesion between contacting fibers within the network. This adhesion is complex as electrospun networks exhibit a variety of contacts, including both cross-cylinder and parallel fiber configu...
Article
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Antler bone displays considerable toughness through the use of a complex nanofibrous structure of mineralized collagen fibrils (MCFs) bound together by non-collagenous proteins (NCPs). While the NCP regions represent a small volume fraction relative to the MCFs, significant surface area is evolved upon failure of the nanointerfaces formed at NCP-co...
Chapter
Focused ion beam (FIB) microscopy provides unprecedented opportunities in isolating discrete volumes of biological material for further experimental studies. While FIB has been historically exploited for preparing relatively thin biological samples for high-resolution transmission electron microscopy, more recent works have applied a range of small...
Article
Graphene oxide (GO) paper is a promising candidate for novel applications in energy storage systems such as electrical batteries, supercapacitors and multi-layered composites where the material undergoes deformation mechanisms. In particular, the strength of graphene oxide paper is critical in such applications and is defined by the interaction bet...
Article
Focused ion beam (FIB) microscopy uses Ga(+) ions to remove material from a sample for a variety of imaging and preparation techniques. While considerable work has examined the effects of FIB exposure on a number of materials, optimized FIB conditions for use with softer polymeric materials are yet to be determined. In this report we use phase cont...
Article
The inelastic deformability of the mineralised matrix in bones is critical to their high toughness, but the nanoscale mechanisms are incompletely understood. Antler is a tough bone type, with a nanostructure composed of mineralised collagen fibrils ∼100nm diameter. We track the fibrillar deformation of antler tissue during cyclic loading using in s...
Article
The depth distribution of a TiO2 pigment within the polyurethane (PU) coil coatings is investigated using step scan phase modulation photoacoustic (SS-PM-PA) FTIR. Coil coatings with different pigment contents were prepared and the modulation frequency (MF) of the SS-PM-PA FTIR varied to record the depth distribution of the pigment within the coati...
Article
Full-text available
Electrospinning using positive and negative polarity applied voltages is used to produce polyamide nanofibers with tailored surface functionality. The surface free energy of the resultant nanofibers is characterized from individual nanofiber wetting experiments. The polar contribution to the total nanofiber surface energy is seen to vary with the p...
Article
Engineered fiber reinforced polymer composites require effective impregnation of polymer matrix within the fibers to form coherent interfaces. In this work, we investigated solution interactions with electrospun fiber mats for the manufacture of nanocomposites with optimized mechanical properties. Void free composites of electrospun nonwoven PA6 na...
Article
The glass transition temperature (Tg) of individual electrospun polymer polyvinyl alcohol fibers of varying diameter was measured using atomic force microscopy (AFM) based nanomechanical thermal analysis. Indentation and bending of individual electrospun fibers using AFM allowed the calculation of the elastic modulus of the polyvinyl alcohol (PVA)...
Article
Bone diseases such as rickets and osteoporosis cause significant reduction in bone quantity and quality, which leads to mechanical abnormalities. However, the precise ultrastructural mechanism by which altered bone quality affects mechanical properties is not clearly understood. Here we demonstrate the functional link between altered bone quality (...
Article
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Surface free energy of mechanically drawn polycarbonate films was determined using contact angle measurements and shown to increase with orientation. The increase in polymer film surface free energy was attributed to increased polymer chain packing during orientation, supported by film density measurements, which provides enhanced intermolecular in...
Article
The mechanical properties of rat bone at micron length scales have been evaluated as a function of environmental conditions using an in situ atomic force microscope (AFM) setup while observing using scanning electron microscopy (SEM). Focused ion beam fabricated rat bone cantilever samples were tested in both low and high vacuum conditions in the S...
Article
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Nanocomposites are used in a range of applications, but have been shown to be particularly effective for mechanical functions [1]. However, this mechanical function is critically dependant on the structural composition of the nanocomposite material. Phase contrast Atomic Force Microscopy (AFM) is an imaging mode of amplitude modulated AFM, whereby...
Article
Full-text available
In this paper we examine the mechanical properties of individual lamellae from bone material using novel atomic force microscopy (AFM)-scanning electron microscopy (SEM) techniques. Individual lamellar beams were selected from bone using focussed ion beam (FIB) microscopy and mechanically deformed with the AFM while observing failure modes using SE...
Article
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Limpet teeth are an example of a biological short fiber reinforced composite material used for a mechanical function. The local micro-scale elastic properties of limpet teeth were examined by bending FIB fabricated beams of the limpet tooth material using atomic force microscopy (AFM). The elastic modulus values for the limpet tooth material varied...
Article
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The mechanical behavior of nanocomposites is critically dependent on their structural composition. In this paper we use Focused Ion Beam (FIB) microscopy to prepare surfaces from a layered polymer nanocomposite for investigation using phase contrast atomic force microscopy (AFM). Phase contrast AFM provides mechanical information on the surface exa...
Article
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A setup is described where an individual electrospun polyamide fiber is attached to an atomic force microscope (AFM) tip and structural information collected with synchrotron micro Fourier transform infrared spectroscopy (μFT-IR). The combination of AFM and synchrotron μFT-IR therefore highlights the potential for recording structure-mechanical pro...
Article
Full-text available
The wetting behavior of polyamide films was modified by depositing electrospun nanofibers manufactured from the same polyamide material. Glycerol contact angles on the film surfaces with low coverage of electrospun nanofibers were successfully predicted using a Cassie-Baxter relationship but could not be predicted for high electrospun nanofiber cov...
Article
Full-text available
A novel technique combining both atomic force microscopy (AFM) and scanning electron microscopy (SEM) is used to test the mechanical properties of densely-packed graphene oxide (GO) paper. Individual beams of GO paper with variable widths were prepared using focussed ion beam (FIB) microscopy and tensile tested to failure using the AFM while observ...
Article
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The surface of polymer nanofibers plays a significant role in many applications thus measurement of their surface properties is essential but challenging due to their relatively small size. This study details AFM wetting tests for individual electrospun Poly (Vinyl Alcohol) nanofibers in order to measure their polar and dispersive surface free ener...
Article
Full-text available
The mechanical properties of individual electrospun polystyrene fibers with sub-micron diameters were measured using a combination of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The strain to failure of the electrospun fibers was observed to increase as the fiber diameter decreased. This size dependent mechanical behavior...
Article
Full-text available
Limpet teeth are striking examples of a biological fibrous nanocomposite consisting of goethite mineral within a polymeric chitin matrix. The mechanical function of limpet teeth is critically dependent on the efficient composite behaviour of goethite, formed as distinct discontinuous nanofibres, reinforcing the matrix. The mechanical properties of...
Article
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Considerable research has focused on the formation of superhydrophobic surfaces utilizing both the chemical composition of surfaces and geometric effects. In this study, a superhydrophobic polycarbonate (PC) network surface was produced from hydrophilic polycarbonate through electrospinning process. Complex surface geometries often related to mater...
Article
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A nanomechanical testing set-up is developed by integrating an atomic force microscope (AFM) for force measurements with a scanning electron microscope (SEM) to provide imaging capabilities. Electrospun nanofibers of polyvinyl alcohol (PVA), nylon-6 and biological mineralized collagen fibrils (MCFs) from antler bone were manipulated and tensile-tes...
Article
The fracture toughness of a noncontinuum fibrous network produced by electrospinning polyamide 6 nanofibers is investigated. The mechanical properties of the nanofiber network is observed to be independent of various incorporated macroscopic crack lengths, resulting in an apparent increase in fracture toughness with increasing crack length as evalu...
Article
Nanofibers of polyamide have been synthesized using electrospinning processes and their wetting properties determined directly from a nanoscale Wilhelmy balance approach. Individual electrospun polyamide nanofibers were attached to atomic force microscope (AFM) tips and immersed in a range of organic liquids with varying polar and dispersive surfac...
Article
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Spray drying was used to encapsulate the paraffin Rubitherm®RT27 with and without carbon nanofibers (CNFs) showing a microencapsulation yield of 63%. Characteristics of microcapsules containing this phase change material (PCM) were dependent on the location in which they were collected in the spray dryer. The mechanical properties of the above-ment...
Article
Full-text available
Bone is a complex material with structural features varying over many different length scales. Lamellae in bone are discrete units of collagen fibril arrays that are the dominant structural feature at length scales of a few microns. The mechanical properties of bone are importantly dependent on the synergy between the lamellae and structural featur...
Article
Full-text available
The glass transition of individual electrospun PVA fibers was found using an AFM fiber bending technique within a heated chamber. A considerably loss in the measured elastic modulus was observed with temperature when the glass transition temperature was reached. The glass transition temperature was observed to decrease as the electrospun PVA fiber...
Article
Full-text available
Discrete volumes of material in the form of a beam have been isolated from a parent limpet tooth using Focused Ion Beam (FIB) techniques. Mechanical bending tests of individual beams are performed using atomic force microscopy (AFM). The relatively small volumes tested in this beam-bending configuration allow approximation of the limpet tooth struc...
Article
Full-text available
Tensile deformation of individual electrospun polyvinyl alcohol (PVA) nanofibres was performed using a novel combination atomic force microscope (AFM)- scanning electron microscope (SEM) technique. The AFM was used to provide manipulation and mechanical testing of individual PVA nanofibers while the SEM was used to observe the deformation process....
Article
Full-text available
A technique combining both atomic force microscopy (AFM) and scanning electron microscopy (SEM) is used to evaluate the mechanical properties of individual collagen fibrils from the fractured surface of antler. SEM is used to locate individual mineralized collagen fibrils and allow visualization of the attachment of these fibrils to the end of an A...
Article
The wetting properties and surface characteristics of individual carbon nanotubes are elucidated by immersing the nanotube into various organic liquid. The resultant force acting on the nanotube can be used to evaluate a liquid contact angle at the nanotube surface from classical methods. This technique was shown to be accurate enough to discern di...