Highly Conformable, Transparent Electrodes for Epidermal Electronics.

We present a highly conformable, stretchable, and transparent electrode for application in epidermal electronics based on polydimethylsiloxane (PDMS) and Ag nanowire (AgNW) networks. With the addition of a small amount of a commercially available nonionic surfactant, Triton X, PDMS became highly adhesive and mechanically compliant, key factors for the development of conformable and stretchable substrates. The polar functional groups present in Triton X interacted with the Pt catalyst present in the PDMS curing agent, thereby hindering the cross-linking reaction of PDMS and modulating the mechanical properties of the polymer. Due to the strong interactions that occur between the polar functional groups of Triton X and AgNWs, AgNWs were effectively embedded in the adhesive PDMS (a-PDMS) matrix, and the highly enhanced conformability, mechanical stretchability, and transparency of the a-PDMS matrix were maintained in the resulting AgNW-embedded a-PDMS matrix. Finally, wearable strain and electrocardiogram (ECG) sensors were fabricated from the AgNW-embedded a-PDMS. The a-PDMS-based strain and ECG sensors exhibited significantly improved sensing performances compared with those of the bare PDMS-based sensors because of the better stretchability and conformability to the skin of the former sensors.

Preclinical assessment of rodent jumping power with a novel electrical stimulation-assisted device.

Sarcopenia is a progressive loss of muscle mass and strength that is associated with increasing the risk of falls, musculoskeletal diseases, and chronic metabolic diseases. However, the animal models adopted to study sarcopenia face limitations since the functional tests conducted on human cannot be directly adapted to animals because the animals do not follow instructions. Moreover, current preclinical research tools for muscle function assessment, such as the rotarod, grip strength, and treadmill, have limitations, including low-intensity simple movements, evaluator subjectivity, and limited power indicators. Hence, in this study, we present a new jumping-power assessment tool in a preclinical rodent model to demonstrate muscle functions. To overcome the light weight and command issues in the rodent model, we developed an electrical stimulation-assisted jump power assessment device. Precisely, the device utilizes a load cell with a 0.1 g resolution and a 50 points/s data acquisition rate to capture the short period of the mouse jump. Additionally, interdigitated electrodes are used to electrically stimulate the mice and make them jump. While our primary focus in this article is the validation of the newly developed jump power assessment device, it is worth noting that this tool has several potential utilities. These include the phenotypic comparison of sarcopenia models, the exploration of muscle function reduction mechanisms, muscle function-related blood biomarkers, and the evaluation of drug intervention effects.

Three-Dimensional Touch Device with Two Terminals.

A crossbar array is an essential element that determines the operating position and simplifies the structure of devices. However, in the crossbar array, wiring numerous electrodes to address many positions poses significant challenges. In this study, a method is proposed that utilizes only two electrodes to determine multiple positions. The method significantly simplifies the wiring and device fabrication process. Instead of defining the node location of the crossbar, it is experimentally demonstrated that the x-y-z coordinates can be determined from i) the resistance change as a function of distance, ii) the resistance variation influenced by the electrode composition, and iii) capacitance fluctuation resulting from changes in the dielectric thickness. By employing two-terminal transparent electrodes, a fully functional 3D touch device is successfully fabricated, introducing a groundbreaking approach to simplify input device architectures.

A fabric-based wearable sensor for continuous monitoring of decubitus ulcer of subjects lying on a bed.

For multifunctional wearable sensing systems, problems related to wireless and continuous communication and soft, noninvasive, and disposable functionality issues should be solved for precise physiological signal detection. To measure the critical transitions of pressure, temperature, and skin impedance when continuous pressure is applied on skin and tissue, we developed a sensor for decubitus ulcers using conventional analog circuitry for wireless and continuous communication in a disposable, breathable fabric-based multifunctional sensing system capable of conformal contact. By integrating the designed wireless communication module into a multifunctional sensor, we obtained sensing data that were sent sequentially and continuously to a customized mobile phone app. With a small-sized and lightweight module, our sensing system operated over 24 h with a coin-cell battery consuming minimum energy for intermittent sensing and transmission. We conducted a pilot test on healthy subjects to evaluate the adequate wireless operation of the multifunctional sensing system when applied to the body. By solving the aforementioned practical problems, including those related to wireless and continuous communication and soft, noninvasive, and disposable functionality issues, our fabric-based multifunctional decubitus ulcer sensor successfully measured applied pressure, skin temperature, and electrical skin impedance.

A Self-Charging Supercapacitor for a Patch-Type Glucose Sensor.

Wearable electronic medical devices measuring continuous biological signals for early disease diagnosis should be small and lightweight for consecutive usability. As a result, there has been an increasing need for new energy supply systems that provide continuous power without any interruption to the operation of the medical devices associated with the use of conventional batteries. In this work, we developed a patch-type self-charging supercapacitor that can measure biological signals with a continuous energy supply without batteries. The glucose oxidase coated on the surface of the microneedle-type glucose sensor encounters glucose in the interstitial fluids of the human body. Electrons created by glucose oxidation operate the self-powered system in which charging begins with the generation of potential differences in supercapacitor electrodes. In an 11 mM glucose solution, the self-powered solid-state supercapacitors (SPSCs) showed a power density of 0.62 mW/cm2, which resulted in self-charging of the supercapacitor. The power density produced by each SPSC with a drop of 11 mM glucose solution was higher than that produced by glucose-based biofuel cells. Consequently, the all-in-one self-powered glucose sensor, with the aid of an Arduino Uno board and appropriate programming, effectively distinguished normal, prediabetic, and diabetic levels from 0.5 mL of solutions absorbed in a laboratory skin model.

In Situ Scanning Electron Microscopy Analysis of the Interfacial Failure of Oxide Scales on Stainless Steels and Its Effect on Sticking during Hot Rolling.

Despite various strategies to address sticking failure in stainless steels (STSs), difficulties in understanding its fundamental mechanisms hinder precise solutions during STS fabrication. This study investigated the effect of chromium (Cr) content on the microstructures and failure modes of oxide scales under a tensile load, simulating the hot-rolling process. The dynamic, real-time behavior of crack initiation, propagation, and interfacial delamination in the oxide scales under tension was analyzed using an in situ scanning electron microscopy (SEM) tensile test. With a high Cr content, iron (Fe) oxide and chromium(III) oxide (Cr2O3) form a layered structure, which is delaminated along the interfaces between the thin Cr2O3 layer and the bulk after perpendicular cracking. The saturated crack densities obtained from in situ SEM provide interfacial strength, while the elastic modulus and hardness obtained from nanoindentation provide vertical fracture strength. In combination with an ex situ elemental image analysis, the in situ SEM results reveal three different failure modes of the four different STSs. The results confirm that sticking failure is more likely to occur as the Cr content increases.

A fabric-based multifunctional sensor for the early detection of skin decubitus ulcers.

Monitoring biosignals at the skin interface is necessary to suppress the potential for decubitus ulcers in immobile patients confined to bed. We develop conformally contacted, disposable, and breathable fabric-based electronic devices to detect skin impedance, applied pressure, and temperature, simultaneously. Based on the experimental evaluation of the multifunctional sensors, a combination of robust AgNW electrodes, soft ionogel capacitive pressure sensor, and resistive temperature sensor on fabric provides alarmed the initiation of early-stage decubitus ulcers without signal distortion under the external stimulus. For clinical verification, an animal model is established with a pair of magnets to mimic a human decubitus ulcers model in murine in vivo. The evidence of pressure-induced ischemic injury is confirmed with the naked eye and histological and molecular biomarker analyses. Our multifunctional integrated sensor detects the critical time for early-stage decubitus ulcer, establishing a robust correlation with the biophysical parameters of skin ischemia and integrity, including temperature and impedance.

Development of a Home Meal Replacement Product Containing Braised Mackerel (Scomber japonicus) with Radish (Raphanus sativus).

The coronavirus disease pandemic has contributed to increasing convenience in food preferences. Home meal replacement (HMR) products are ready-to-eat, -cook, or -heat foods, providing convenience for consumers. We developed a HMR product containing mackerel as a protein- and lipid-rich source using various food-processing technologies to maintain its nutritional content and prolong shelf life. The HMR product contained mackerel, radish, and sauce in a ratio of 5:1:4. Raw frozen mackerels were thawed by using a high-frequency defroster before being braised using a superheated steam roaster. Response surface methodology was employed to obtain the optimal heating conditions of 181 °C for 9 min. The final test HMR product was packed in a polypropylene plastic bowl prior to freezing at -35 °C for 1 h using a quick freezing system. The HMR product developed using these technologies exhibited stable microbiological and chemical properties for 90 days of storage. Sensory scores gradually decreased with increasing storage temperature and time. Protein content in the HMR product was 13%, 40% of which comprised essential amino acids; lipid content was 13.4%, 18% of which was composed of docosahexaenoic acid. The HMR product can preserve its quality and is considered safe for consumption for up to 40 months of storage at -18 °C.

Using Electrospun AgNW/P(VDF-TrFE) Composite Nanofibers to Create Transparent and Wearable Single-Electrode Triboelectric Nanogenerators for Self-Powered Touch Panels.

Self-powered sensors have attracted significant interest for individual wearable device operation. Here, transparent and wearable single-electrode triboelectric nanogenerators (SETENGs) with high power generation are created using electrospun Ag nanowires (AgNWs)/poly(vinylidenefluoride-cotrifluoroethylene) [P(VDF-TrFE)] composite nanofibers (NFs). The SETENGs generate an output power density of up to 217 W/m2 with repetitive contact and separation from the surface of a latex glove. In electrospun P(VDF-TrFE) NFs, the crystalline ß-phase is highly oriented by oxygen-containing functional groups on the surface of AgNWs, endowing the F-rich surface with high electron negativity and enabling efficient triboelectrification. Additionally, 80% transmittance at a light wavelength of 550 nm, mechanical stability, and durability after 10 000 cycles at 10% strain are confirmed by filling the NF pores with plasma desorption mass spectrometry. Our SETENG acts as an effective energy harvester by powering 45 light-emitting diodes and as an excellent real-time, self-powered touch panel.

Wearable and Transparent Capacitive Strain Sensor with High Sensitivity Based on Patterned Ag Nanowire Networks.

In this study, a transparent and stretchable thin-film capacitive strain sensor based on patterned Ag nanowire networks (AgNWs) was successfully fabricated. The AgNWs were patterned using a capillary force lithography (CFL) method and were embedded onto the surface of the polydimethylsiloxane substrate. The strain (ε) sensitivity of the capacitive strain sensor was controlled and enhanced by patterning the AgNWs into electrodes with an interdigitated shape. The interdigitated capacitive strain sensor (ICSS) is expected to have -1.57 gauge factor (GF) at 30% ε by calculation, which is much higher than the sensitivity of typical parallel-plate-type capacitive strain sensors. Because of the interdigitated pattern of the electrodes, the GF of the ICSS was increased up to -2.0. The ICSS had no hysteresis behavior up to ε values of 15% and showed stable ε sensing performance during the repeated stretching test at ε values of 10% for 1000 cycles. Furthermore, there was no cross talk between ε and pressure sensing in the AgNW-based ICSS, which was found to be insensitive to externally applied pressure. The ICSS was then used to detect the finger and wrist muscle motions of the human body to simulate its application to large and small ε sensing.