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Abstract With technological advances in wearable health care monitoring system, there increasing demands for the patterning technology for reliable sensors. Dry-film photoresists (DFRs) have several advantages for the patterning of silver nanowires (AgNWs), including cost-effectiveness, low toxicity of the process, and ease of mass production through a roll-to-roll process. In this study, using DFRs, we achieved the facile fabrication of AgNW-based chips for optical detection of myoglobin (Mb) via surface-enhanced Raman spectroscopy (SERS). Mb is found in accessible biological fluids such as urine and serum, which is a representative protein biomarker for human health monitoring. AgNWs were successfully patterned on polyethylene terephthalate films using DFR to form multiple spots, with a diameter of ~500 µm, that are available for detection. SERS spectra showed that the AgNW chips can efficiently detect myoglobin proteins down to levels of clinical significance. Our results will provide insights for the cost-effective production method of futuristic health care monitoring system.

With the technological progress of wearable electronics operated in 5 G network communication system, a stretchable noise suppressor at GHz bandwidth that is reliable under severe deformation coming from the user’s motion should be developed. However, current material systems for the noise suppressor showed a limited stretchability. This study introduces a carbonyl iron powder – polydimethylsiloxane (CIP – PDMS) composite with partially bonded interface as a solution to enhance the stretchability. Modulation of CIP surface to have the partial interface bonding (CIP-PID) results in the ultra large strain of ~165% even at the 40 vol% of CIP-PIDs, while only ~71% of strain is observed for CIPs with the full interface bonding (CIP-FID). According to a microstructural analysis and FEM simulation of the strained composite specimens, when partially bonded to CIP at the interface, the PDMS matrix forms a free surface that can be deformed like pure PDMS, resulting in high stretchability. The wettability of CIP offers protection against eddy current loss while retaining strong magnetic properties, suppressing the EM noise. Thus, the approach eliminates the tradeoff between EM suppression and stretchability.

Precise measurement of the surface energy of nanoscale metal thin films is crucial for the fabrication of reliable miniaturized electronic devices consisting of multi-stacked thin film strips. However, the conventional method utilizing sessile drops to measure the surface energy is not suitable for nanoscale samples owing to the much larger size of the liquid droplets than those of the samples being measured. Herein, nCA-AFM (nano contact angle-atomic force microscopy) based on PF-QNM (PeakForce quantitative nanomechanical mapping) imaging mode is explored as a novel tool to measure the surface energy of nanoscale Au strips. Au strips with thicknesses of 50 and 100 nm were patterned to have widths in a range from 200 to 500 nm. The surface energy of the nano-patterned Au strips measured with PF-QNM methods revealed that grain size is the most important factor determining the surface energy. The sample having different widths with the same grain size showed similar surface energy values, regardless of the sample dimensions. Our results highlight that grain size control is required to achieve the target surface energy of metal strips for applications in nanoscale electronic devices.

Achieving resistance to sedimentation of carbonyl iron powders (CIPs) in ethanol is important to fabricate reliable magnetorheological suspensions. The traditional method to improve the sedimentation stability is to add dispersants, but this approach can suffer from high costs and toxicity of added surfactants. In this study, the surface of CIPs was modified with 3-aminopropyl triethoxysilane (APTES) or tetraethyl orthosilicate (TEOS) to enhance the sedimentation stability of CIP suspensions without using toxic dispersants. After coating APTES or TEOS on the CIP surface, the surface energy of the CIP powders increased, which was attributed to the increased amino or hydroxyl groups on the CIP surface due to APTES or TEOS, respectively. The Gibbs free wetting enthalpy (ΔG) was calculated to evaluate the wettability of the modified CIPs, and APTES@CIPs or TEOS@CIPs had a low ΔG, indicating that both had a high thermodynamic spontaneity of wetting in ethanol. The enhanced wettability due to APTES or TEOS coating resulted in low CIP agglomeration, which resulted in APTES@CIPs or TEOS@CIPs dispersions having smaller average particle sizes than pure CIP dispersions. Therefore, APTES@CIPs or TEOS@CIPs showed more than 2 times slower sedimentation velocity than pure CIPs, resulting in enhanced sedimentation stability.

The fibrous supercapacitor is a promising candidate for wearable energy-storage systems due to excellent mechanical reliability under deformation. In this study, a mechanically reliable fibrous supercapacitor with high volumetric power density and energy density was developed using fiber electrodes composed of multilayered active materials coated on silk yarns. The conductive silk yarn electrodes are fabricated via a sequential dip-coating process of silver nanowires, multi-walled carbon nanotubes (MWCNT, three to seven walls), and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The composite-coated silk yarn electrodes were stable under cyclic bending as well as under washing in water. Due to the synergetic effect of the three conducting materials, an excellent electrochemical performance was obtained resulting in high volumetric energy and power densities of 8–13 mWh cm−3 and 8–19 W cm−3, respectively. A yarn-type supercapacitor was demonstrated by integrating composite-coated silk yarn electrodes with a hydrogel electrolyte, showing a promising stability as evidenced by the retention of over 94% and 93% of the specific capacitance after 90-degree bending and stretching.