Beomjoon Kim

The University of Tokyo | Todai · Center for International Research on Micronano Mechatronics (CIRMM)

Colorimetric assays rely on detecting colour changes to measure the concentration of target molecules. Paper substrates are commonly used for the detection of biomarkers due to their availability, porous structure, and capillarity. However, the morphological and mechanical properties of paper, such as fibre diameter, pore size, and tensile strength...

Properly handling animals and understanding their habits are crucial to establish a society where humans and animals coexist. Thus, identifying individual animals, including their possessions, and adequately managing each animal is necessary. Although several conventional identification methods exist, such as the use of ear punch, tattoos, and radi...

As one of the promising human—machine interfaces, wearable sensors play an important role in modern society, which advances the development of wearable fields, especially in the promising applications of electronic skin (e-skin), robotics, prosthetics, and healthcare. In the last decades, wearable sensors tend to be capable of attractive capabiliti...

The surface activated bonding (SAB) technique enables room temperature bonding of metals, such as Au, by forming metal bonds between clean and reactive surfaces. However, the re-adsorption on the activated surface deteriorates the bonding quality, which limits the applicability of SAB for actual packaging processes of electronics. In this study, we...

Infectious diseases are among the leading causes of mortality worldwide. A new coronavirus named severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) was identified in Wuhan, China in 2019, and the World Health Organization (WHO) declared its outbreak, coronavirus disease 2019 (COVID-19), as a global pandemic in 2020. COVID-19 can spread q...

Light-based therapy is an emerging treatment for skin cancer, which has received increased attention due to its drug-free and non-invasive approach. However, the limitation of current light therapy methods is the inability for light to penetrate the skin and reach deep lesions. As such, we have developed a polylactic acid (PLA) microneedles array a...

A microneedle (MN) array is a novel biomedical device adopted in medical applications to pierce through the stratum corneum while targeting the viable epidermis and dermis layers of the skin. Owing to their micron-scale dimensions, MNs can minimize stimulations of the sensory nerve fibers in the dermis layer. For medical applications, such as wound...

Minimally invasive biosensing using microneedles (MNs) is a desirable technology for continuous healthcare monitoring. Among a wide range of MNs, porous MNs are expected to be applied for sampling of interstitial fluids (ISF) by connecting the internal tissue to external measurement devices. In order to realize a continuous measurement of biomarker...

In the past two decades, microneedles (MNs), as a painless and simple drug delivery system, have received increasing attention for various biomedical applications such as transdermal drug delivery, interstitial fluid (ISF) extraction, and biosensing. Among the various types of MNs, porous MNs have been recently researched owing to their distinctive...

With the rapid development of the Internet of Things (IoT) and the emergence of 5G, traditional silicon-based electronics no longer fully meet market demands such as nonplanar application scenarios due to mechanical mismatch. This provides unprecedented opportunities for flexible electronics that bypass the physical rigidity through the introductio...

Stretchable triboelectric nanogenerators (TENGs) attract much attentions in the field of wearable electronics owing to their unique capabilities of ambient energy harvesting, especially from human activities, serving as sustainable power source as well as functional sensing device. The essential challenge of super-stretchable triboelectric nanogene...

Abstract To pierce through the skin and interact with the first biofluid available, microneedles should be mechanically strong. However, some polymers used to fabricate microneedles yield insufficient strength for the fabrication of arrays (PDMS, highly porous structures, etc.). To enhance mechanical properties, piercing materials can be used. They...

Microneedle (MN) is a key technology of the biomedical engineering field due to its capability of accessing the biological information in a minimally invasive manner. One of the huge demands for next-generation healthcare monitoring is continuous monitoring, especially of blood glucose concentration. For this, MN should be kept inserted into the hu...

With a huge demand from the society on a more precise and rapid biological molecule detection in a reduced amount of biosamples, biomedical engineering technology has been in rapid development, resulting in a wide range of biosensors using microfluidic systems. For microfluidic structure, glass is still the main material owing to its chemical stabi...

Microneedles are designed for piercing the stratum corneum and delivering drugs into the epidermis and dermis layers of the skin. Their micrometric dimension causes minor or negligible stimulations to sensory nerve fibers in the dermis layer of the skin, making drug administration through microneedles less painful compared to conventional hypodermi...

The triboelectric nanogenerator (TENG) is an emerging technology that can convert mechanical energy generated by human motion into electricity, and it is expected to compensate batteries for driving wearable electronics. However, in the field of wearable TENGs, low cost and common wearable raw material, which is critical for daily use, cannot gener...

Miniaturized and mobile liquid handling devices are essential elements to biological or clinical applications. This will innovate the conventional liquid handling methods such as manual or automated pipetting systems. Here, we propose the micro fractal pipette as the candidate device for this objective. It is made of epoxy polymer and printed by in...

The cover image is based on the Research Article Porous microneedles on a paper for screening test of prediabetes by Hakjae Lee et al., https://doi.org/10.1002/mds3.10109.

Porous microneedles are expected to have a variety of potential for applications in diagnostics owing to their ability to penetrate human skin painlessly and extract bio‐fluid by capillary action. In this paper, a “Porous Microneedle on a Paper substrate” (PMP) is proposed as a novel platform for direct integration of sensors. A microneedle array w...

Triboelectric nanogenerators (TENGs) have proven to be a robust power source for efficiently converting environmental mechanical energy into electricity. Triboelectric technology experienced substantial growth in the past few years, especially in the field of green wearable power sources as the Internet of Things develops. However, it is still diff...

A novel single-layer structured triboelectric generator (TEG) is proposed with a hybrid mix of carbon nanotube (CNT) and silk. Here, the mixing of two materials in liquid phase for proven effective power generation is shown. In this research, CNT provides the function of conductivity, whereas silk fibroin forms the main triboelectric generation mat...

In anticancer drug development, it is important to simultaneously evaluate both the effect of drugs on cell proliferation and their ability to penetrate tissues. To realize such an evaluation process, here, we present a compartmentalized tumor spheroid culture system utilizing a thin membrane with a through-hole to conduct localized anticancer trea...

3D printing is attracting considerable interest for its capacity to produce prototypes and small production runs rapidly. Fused deposit modeling (FDM) was used to produce polyvalent test plates for investigation of the physical, chemical, and in-vitro biological properties of printed materials. The polyvalent test plates (PVTPs) are poly-lactic aci...

Inhibition of H3N2 influenza PA endonuclease activity by a panel of anionic calix[n]arenes and β-cyclodextrin sulfate has been studied. The joint experimental and theoretical results reveal that the larger, more flexible and highly water-soluble sulfonato-calix[n]arenes have high inhibitory activity, with para-sulfonato-calix[8]arene, SC8, having a...

Porous microneedles (MNs) are expected to be applied for diagnostic microfluidic devices such as blood glucose monitoring as they enable a pain-free penetration of human skin and the extraction of interstitial fluids. However, conventional microfluidic systems require additional steps to separate the liquid from a porous structure used for fluid ex...

Microneedles (MNs) have been established as promising medical devices as they are minimally invasive, cause less pain, and can be utilized for self-administration of drugs by patients. There has been rapid development in MNs for transdermal monitoring and diagnostic systems, following the active research on fabrication methods and applications for...

After publication of this article [1], the author noticed there are some conversion errors with the below characters and units in the article body text. The corrections are detailed below.

In this work, localized porous silicon structures were fabricated using patterned illumination by shadow masks. For comparative analysis, selective formation of porous silicon structures was performed using metal (chromium) and insulating (SU-8 photoresist) masking layers. Various porous structures were fabricated and the types of silicon substrate...

This paper reports a hybrid energy harvesting approach which combines triboelectricity and piezoelectricity based on low-frequency (less than 5 Hz, such as environmental vibrations) stochastic resonance. A vibration configuration was well designed to enhance the conversion efficiency of mechanical energy to electricity via the stochastic vibration...

Wearable electronics experienced a blooming prosperity in the past decade due to their trend of miniaturization and smart functions integration, and the appealing intrinsic physical properties, such as flexibility, stretchability, and conformability. Although wearable electronics play an important role in modern society, either as sensing devices f...

Calix[4]arene dihydroxyphosphonic acid has been demonstrated to possess an interesting range of biological properties, including atypical anti-cancer activity. The robustness of calix[4]arene dihydroxyphosphonic acid and its ubiquitous dimeric motif offers perspectives for pre-defined solid state complexation with small molecules. In the current ar...

The couple Calix[4]arene-1,3-O-diphosphorous acid (C4diP) and zinc ions (Zn2+) acts as a synergistic DNA binder. Silicon NanoTweezer (SNT) measurements show an increase in the mechanical stiffness of DNA bundles by a factor of >150, at Zn2+ to C4diP ratios above 8, as compared to Zinc alone whereas C4diP alone decreases the stiffness of DNA. Electr...

We examine the effect of physiological cations Na⁺, K⁺, Mg²⁺, and Ca²⁺ on the mechanical properties of bundles of λ-phage DNA using silicon nanotweezers (SNTs). Integrating SNTs with a microfluidic device allows us to perform titration experiments while measuring the effect in real-time. The results show that only for Mg²⁺ and in particular, at the...

This paper describes a modified dry peel-off process for the fabrication of gold micro heaters embedded in polydimethylsiloxane (PDMS), the characterization of the micro heaters, and the comparison of the measured results with simulated data. The modified dry peel-off process utilizes the difference in molecular adhesion between gold, amine (NH2),...

Triboelectric nanogenerator (TENG) has proven to be a robust power source to efficiently convert ambient mechanical energy into electricity. It experienced substantial growth in the past years owing to its appealing features that make it superior than other self-powering principles. In particular, it excels in high output performance, sustainabilit...

This paper describes the fabrication method that a lead zirconate titanate (PZT) thin film capacitor, which is formed on a Si substrate by metal organic decomposition (MOD), can be easily transferred to flexible polymer (polydimenthylsiloxane; PDMS) without additional chemical contamination. The thin film capacitor is composed of sandwich structure...

Monitoring biological reactions using the mechanical response of macromolecules is an alternative approach to immunoassays for providing real-time information about the underlying molecular mechanisms. Although force spectroscopy techniques, e.g. AFM and optical tweezers, perform precise molecular measurements at the single molecule level, sophisti...

Continuous fabrication of micropatterns at low-cost is attracting attention in various applications within industrial fields. To meet such demands, we have demonstrated a roll contact printing technique, using roller type polydimethylsiloxane (PDMS) stamps with roll-to-flat and roll-to-roll stages. Roller type PDMS stamps for roll contact printing...

The isolation of single biological cells and their further cultivation in dedicated arrayed chambers are key to the collection of statistically reliable temporal data in cell-based biological experiments. In this work, we present a hydrodynamic single cell trapping and culturing platform that facilitates cell observation and experimentation using s...

This letter reports on a novel fabrication method of 3D metal nanostructures using high-throughput nanostencil lithography. Aperture clogging, which occurs on the stencil membranes during physical vapor deposition, is leveraged to create complex topographies in nanoscale. Precision of the 3D nanofabrication method is studied in terms of geometric p...

This paper describes extremely simple configuration of novel vibrational energy harvester, which can harness low frequency (less than 5 Hz, such as various environmental vibrations) over a broad frequency band for the first time. A design that utilizes a phenomenon called stochastic resonance can give significantly enhanced vibration mode for incre...

In recent years, a new electrification-based mechanism called triboelectric generator (TEG) has been demonstrated as a stable and renewable power source to convert ambient energy into remarkable electrical output. Various TEG configurations have been proposed to enhance the output performance focusing on improvements to its working principle and st...

This paper describes the fabrication method that a lead zirconate titanate (PZT) thin film capacitor, which is formed on a Si substrate by metal organic decomposition (MOD), can be easily transferred to flexible polymer (polydimethylsiloxane; PDMS) without additional chemical contamination. The thin film capacitor is composed of sandwich structure...

During the 10 last years, there has been a growing interest in calix[n]arene capped silver nanoparticles for their uses in biosensing and much more recently for their intrinsic therapeutic properties. Cost effective, portable and ultra-sensitive analytical tools are one of the major expectations of silver nanoparticles capped with calix[n]arenes. T...

This paper shows thermal measurement and analysis of a microfluidic device integrated with local thin film heater. Thermal analysis was calculated by finite element modeling. Electrical property of the micro heater was calibrated in advance of the thermal analysis due to the difference from the bulk property of Pt. The thermal analysis results agre...

This paper reports a simple and disposable polymer microwells chip to investigate single cell level of Red Blood Cells (RBCs) in parallel analysis with fast imaging. This method is based on the image processing method and microfluidic device that has microwells for single cell trapping. The RBCs are trapped in the microwells just by gravity. After...

This paper describes a new transfer method to realize wearable devices with embedded capacitors providing high permittivities and thinner structures. To miniaturize passive elements, such as capacitor on flexible substrate[1], lead zirconate titanate (PZT) thin films are formed on a Si substrate by MOD (metal organic decomposition) method, then can...

In vitro microvascular models have been interested in the fields of regenerative medicine and drug development. Here, we successfully fabricated a 3D in vitro microvasculature composed by human umbilical endothelial cells completely surrounded by the collagen gel. We examined development of cell stress fibers, nucleus alignment and the diameter cha...

summarized the reported research work on the high-performance triboelectric nanogenrator (TENG) for wearable electronics. The requirement of TENG for wearable electronics was illustrated firstly, and then the developing tendency of flexible TENGs was figured out. Based on both the above analysis and reviewing the latest publications, the recent pro...

This paper proposes a novel device of enhanced energy harvesting from stochastic resonant vibration, which can utilize ambient vibration with wideband and low frequencies. The suggested bi-stable cantilever was modeled using three kinds of numerical simulations and the feasibility of the stochastic resonant vibration can be confirmed by using ambie...

The present paper describes a modified dry peel-off process to fabricate stable gold micro electrode with polyimide (PI) embedded in a polydimethlysiloxane (PDMS) substrate. three kinds of self-assembled monolayer (SAM) were employed to control adhesion strength and to transfer gold micro electrodes from silicon substrate in driect.

In this paper, we propose the method that PZT thin layer, which is formed on a Si substrate, can be transferred to polydimethylsiloxane (PDMS) without additional chemical contamination. In consideration of embedding in the substrate more easily, sandwich structures of PZT between two metal layers are used as thin-film capacitor. To embed PZT in the...