Flexible and highly ordered nanopillar electrochemical sensor for sensitive insulin evaluation.

In line with growing interest in obesity management, there has been an increase in the amount of research focused on highly sensitive analysis systems for a small number of biomarers. In this paper, we introduce the highly ordered nanopillar electrode, featuring a high aspect ratio surface area that enables enhanced electron transfer. For fabrication of the flexible electrode, gold was evaporated by electronic beam lithography on polyurethane (PU), which has high flexibility.

Se-Rich MoSe Nanosheets and Their Superior Electrocatalytic Performance for Hydrogen Evolution Reaction.

Two-dimensional MoSe has emerged as a promising electrocatalyst for the hydrogen evolution reaction (HER), although its catalytic activity needs to be further improved. Herein, we report Se-rich MoSe nanosheets synthesized using a hydrothermal reaction, displaying much enhanced HER performance at the Se/Mo ratio of 2.3.

Combinatorial biophysical cue sensor array for controlling neural stem cell fate.

Biophysical cues, such as electrical stimulus, mechanical feature, and surface topography, enable the control of neural stem cell (NSC) differentiation and neurite outgrowth. However, the effect of these biophysical cues on NSC behavior has not been fully elucidated. In the present study, we developed an innovative combinatorial biophysical cue sensor array combining a surface modified nanopillar array with conductive hydrogel micropatterns.

Ruthenium Nanoparticles on Cobalt-Doped 1T' Phase MoS Nanosheets for Overall Water Splitting.

2D MoS nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co-Ru-MoS hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T' phase MoS nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles.

Development of zinc oxide-based sub-micro pillar arrays for on-site capture and DNA detection of foodborne pathogen.

Prevention and early detection of bacterial infection caused by foodborne pathogens are the most important task to human society. Although currently available diagnostic technologies have been developed and designed for detection of specific pathogens, suitable capturing tools for the pathogens are rarely studied. In this paper, a new methodology is developed and proposed to realize effective capturing through touchable flexible zinc oxide-based sub-micro pillar arrays through genetic analysis.

Preparation of ultrathin defect-free graphene sheets from graphite via fluidic delamination for solid-contact ion-to-electron transducers in potentiometric sensors.

In this study, ultrathin and defect-free graphene (Gr) sheets were prepared through a fluid dynamics-induced shear exfoliation method using graphite. The high hydrophobicity and surface area of Gr make it attractive as a solid-contact ion-to-electron transducer for potentiometric K sensors, in which the electrodes are fabricated through a screen-printing process. The electrochemical characterization demonstrates that Gr solid contact results in a high double-layer capacitance, potential stability, and strong resistance against water layer, gases, and light.

Flexible Two-Dimensional TiC MXene Films as Thermoacoustic Devices.

MXenes have attracted great attention for their potential applications in electrochemical and electronic devices due to their excellent characteristics. Traditional sound sources based on the thermoacoustic effect demonstrated that a conductor needs to have an extremely low heat capacity and high thermal conductivity. Hence, a thin MXene film with a low heat capacity per unit area (HCPUA) and special layered structure is emerging as a promising candidate to build loudspeakers.

Binarized Neural Network with Silicon Nanosheet Synaptic Transistors for Supervised Pattern Classification.

In the biological neural network, the learning process is achieved through massively parallel synaptic connections between neurons that can be adjusted in an analog manner. Recent developments in emerging synaptic devices and their networks can emulate the functionality of a biological neural network, which will be the fundamental building block for a neuromorphic computing architecture. However, on-chip implementation of a large-scale artificial neural network is still very challenging due to unreliable analog weight modulation in current synaptic device technology.

Multifunctional hand-held sensor using electronic components embedded in smartphones for quick PCR screening.

We focused on the development of a hand-held pathogen-detection device using smartphone-embedded electronic elements combined with functionalized magnetic particles (MPs) and sepharose. To perform affinity chromatography for evaluating DNA amplicons, avidin-conjugated MPs and succinimide-linked sepharose were used with biotin-primers. To mimic the centrifugal-based affinity ligand chromatography, a smartphone-mountable low-power fan was plugged into the charging port of a smartphone.

Enhanced Selectivity of MXene Gas Sensors through Metal Ion Intercalation: In Situ X-ray Diffraction Study.

Gas molecules are known to interact with two-dimensional (2D) materials through surface adsorption where the adsorption-induced charge transfer governs the chemiresistive sensing of various gases. Recently, titanium carbide (TiCT ) MXene emerged as a promising sensing channel showing the highest sensitivity among 2D materials and unique gas selectivity. However, unlike conventional 2D materials, MXenes show metallic conductivity and contain interlayer water, implying that gas molecules will likely interact in a more complex way than the typical charge transfer model.

Mechanical and Electrical Reliability Analysis of Flexible Si Complementary Metal-Oxide-Semiconductor Integrated Circuit.

A flexible Si complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) with multi-level interconnects is realized by thinning down and transferring the CMOS IC onto a polymer substrate. A detailed mechanical and electrical reliability analysis of the flexible Si CMOS IC is carried out in relation to the neutral mechanical plane (NMP) that is extracted from both analytical and numerical modeling. To enhance the reliability by optimizing the NMP position, the thicknesses of all the layers in the CMOS IC on the polymer substrate are carefully adjusted.

Potentiometric performance of flexible pH sensor based on polyaniline nanofiber arrays.

We report potentiometric performance of a polyaniline nanofiber array-based pH sensor fabricated by combining a dilute chemical polymerization and low-cost and simple screen printing process. The pH sensor had a two-electrode configuration consisting of polyaniline nanofiber array sensing electrode and Ag/AgCl reference electrode. Measurement of electromotive force between sensing and reference electrodes provided various electrochemical properties of pH sensors.

Naked eye detection of an amplified gene using metal particle-based DNA transport within functionalized porous interfaces.

The current study focuses on developing a system for visually detecting an amplified bacterial (Escherichia coli O157:H7) gene using a heavy metal particle (MP) and functionalized porous sepharose gel. To functionalize DNA-specificity to the MP, an avidin-modified MP was employed in combination with a biotin-conjugated primer. The porous sepharose matrix was functionalized with an amine-reactive group, such as N-hydroxysuccinimide (NHS), to achieve separation upon binding of the amplified gene.

A Disposable and Multi-Chamber Film-Based PCR Chip for Detection of Foodborne Pathogen.

Since the increment of the threat to public health caused by foodborne pathogens, researches have been widely studied on developing the miniaturized detection system for the on-site pathogen detection. In the study, we focused on the development of portable, robust, and disposable film-based polymerase chain reaction (PCR) chip containing a multiplex chamber for simultaneous gene amplification. In order to simply fabricate and operate a film-based PCR chip, different kinds of PCR chambers were designed and fabricated using polyethylene terephthalate (PET) and polyvinyl chloride (PVC) adhesive film, in comparison with commercial PCR, which employs a stereotyped system at a bench-top scale.

A microfluidic electrochemical aptasensor for enrichment and detection of bisphenol A.

Bisphenol A (BPA) is an organic monomer used to make common consumer goods such as plastic containers, sports equipment, and cosmetics which are heavily produced worldwide. A growing interest has been drawn to general public as BPA is one of the major endocrine disrupting chemicals threating human health. To date, numerous BPA sensors have been attempted to be developed but important challenges still remained such as limited linearity range, easy to use, and long term response time.

Ultrasonic fabrication of flexible antibacterial ZnO nanopillar array film.

Antibacterial activity is essential and highly demanded in worldwide to prevent potential bacterial infection. Here in this work, we report a new approch for the fabrication of flexible zinc oxide nanopillar arrays (ZG-NPA) film with an efficient antibacterial activity. A flexible NPA film served as a substrate for the rapid formation of ZnO by using ultrasound-assisted method.

Flexible nanopillar-based electrochemical sensors for genetic detection of foodborne pathogens.

Flexible and highly ordered nanopillar arrayed electrodes have brought great interest for many electrochemical applications, especially to the biosensors, because of its unique mechanical and topological properties. Herein, we report an advanced method to fabricate highly ordered nanopillar electrodes produced by soft-/photo-lithography and metal evaporation. The highly ordered nanopillar array exhibited the superior electrochemical and mechanical properties in regard with the wide space to response with electrolytes, enabling the sensitive analysis.

Non-fluorescent nanoscopic monitoring of a single trapped nanoparticle via nonlinear point sources.

Detection of single nanoparticles or molecules has often relied on fluorescent schemes. However, fluorescence detection approaches limit the range of investigable nanoparticles or molecules. Here, we propose and demonstrate a non-fluorescent nanoscopic trapping and monitoring platform that can trap a single sub-5-nm particle and monitor it with a pair of floating nonlinear point sources.

A film-based integrated chip for gene amplification and electrochemical detection of pathogens causing foodborne illnesses.

Given the increased interest in public hygiene due to outbreaks of food poisoning, increased emphasis has been placed on developing novel monitoring systems for point-of-care testing (POCT) to evaluate pathogens causing foodborne illnesses. Here, we demonstrate a pathogen evaluation system utilizing simple film-based microfluidics, featuring simultaneous gene amplification, solution mixing, and electrochemical detection. To minimize and integrate the various functionalities into a single chip, patterned polyimide and polyester films were mainly used on a polycarbonate housing chip, allowing simple fabrication and alignment, in contrast to conventional polymerase chain reaction, which requires a complex biosensing system at a bench-top scale.

Three-Dimensional Printed Poly(vinyl alcohol) Substrate with Controlled On-Demand Degradation for Transient Electronics.

Electronics that degrade after stable operation for a desired operating time, called transient electronics, are of great interest in many fields, including biomedical implants, secure memory devices, and environmental sensors. Thus, the development of transient materials is critical for the advancement of transient electronics and their applications. However, previous reports have mostly relied on achieving transience in aqueous solutions, where the transience time is largely predetermined based on the materials initially selected at the beginning of the fabrication.

Three-Dimensionally Printed Micro-electromechanical Switches.

Three-dimensional (3D) printers have attracted considerable attention from both industry and academia and especially in recent years because of their ability to overcome the limitations of two-dimensional (2D) processes and to enable large-scale facile integration techniques. With 3D printing technologies, complex structures can be created using only a computer-aided design file as a reference; consequently, complex shapes can be manufactured in a single step with little dependence on manufacturer technologies. In this work, we provide a first demonstration of the facile and time-saving 3D printing of two-terminal micro-electromechanical (MEM) switches.

An Ultrastable Ionic Chemiresistor Skin with an Intrinsically Stretchable Polymer Electrolyte.

Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound (VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices.

Material-Independent Nanotransfer onto a Flexible Substrate Using Mechanical-Interlocking Structure.

Nanowire-transfer technology has received much attention thanks to its capability to fabricate high-performance flexible nanodevices with high simplicity and throughput. However, it is still challenging to extend the conventional nanowire-transfer method to the fabrication of a wide range of devices since a chemical-adhesion-based nanowire-transfer mechanism is complex and time-consuming, hindering successful transfer of diverse nanowires made of various materials. Here, we introduce a material-independent mechanical-interlocking-based nanowire-transfer (MINT) method, fabricating ultralong and fully aligned nanowires on a large flexible substrate (2.

An Optical Biosensing Strategy Based on Selective Light Absorption and Wavelength Filtering from Chromogenic Reaction.

To overcome the time and space constraints in disease diagnosis via the biosensing approach, we developed a new signal-transducing strategy that can be applied to colorimetric optical biosensors. Our study is focused on implementation of a signal transduction technology that can directly translate the color intensity signals-that require complicated optical equipment for the analysis-into signals that can be easily counted with the naked eye. Based on the selective light absorption and wavelength-filtering principles, our new optical signaling transducer was built from a common computer monitor and a smartphone.

Nanotransplantation Printing of Crystallographic-Orientation-Controlled Single-Crystalline Nanowire Arrays on Diverse Surfaces.

The fabrication of a highly ordered array of single-crystalline nanostructures prepared from solution-phase or vapor-phase synthesis methods is extremely challenging due to multiple difficulties of spatial arrangement and control of crystallographic orientation. Herein, we introduce a nanotransplantation printing (NTPP) technique for the reliable fabrication, transfer, and arrangement of single-crystalline Si nanowires (NWs) on diverse substrates. NTPP entails (1) formation of nanoscale etch mask patterns on conventional low-cost Si via nanotransfer printing, (2) two-step combinatorial plasma etching for defining Si NWs, and (3) detachment and transfer of the NWs onto various receiver substrates using an infiltration-type polymeric transfer medium and a solvent-assisted adhesion switching mechanism.