This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm² and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent.

This paper describes the surface-patterned polydimethylsiloxane (PDMS) pillar arrays for enhancing cell alignment and contraction force in cardiomyocytes. The PDMS micropillar (μpillar) arrays with microgrooves (μgrooves) were fabricated using a unique micro-mold made using SU-8 double layer processes. The spring constant of the μpillar arrays was experimentally confirmed using atomic force microscopy (AFM). After culturing cardiac cells on the two different types of μpillar arrays, with and without grooves on the top of μpillar, the characteristics of the cardiomyocytes were analyzed using a custom-made image analysis system. The alignment of the cardiomyocytes on the μgrooves of the μpillars was clearly observed using a DAPI staining process. The mechanical force generated by the contraction force of the cardiomyocytes was derived from the displacement of the μpillar arrays. The contraction force of the cardiomyocytes aligned on the μgrooves was 20% higher than that of the μpillar arrays without μgrooves. The experimental results prove that applied geometrical stimulus is an effective method for aligning and improving the contraction force of cardiomyocytes.

Engineering high-performance carbonaceous electrode materials from earth-abundant biomass has attracted substantial attention for its applicability in next-generation supercapacitors (SCs). However, these materials exhibit low specific energy due to the dominance of mesopores and a limited potential window. To overcome these shortcomings, herein, we synthesize Miscanthus sinensis (silver grass)-derived hierarchically-porous activated carbons (SHACs) via pyrolysis, carbonization, and KOH activation. We test the SHAC electrodes with different electrolytes, showing how an electrolyte–electrode pair can be tuned to boost energy and power densities. Owing to the synergetic effect of the size-balanced proportion of micropores matched with the size of electrolyte ions, in KOH electrolyte, the SHAC electrode produces a high specific capacitance (592 F g⁻¹) while, simultaneously, providing faster charging compared to Na₂SO₄ electrolyte. We rationalize these findings with molecular dynamics simulations, demonstrating the avoidance of power-density trade-off, typical for microporous SCs. Upon adding K₃Fe(CN)₆ redox species to KOH electrolyte (hybrid electrolyte), capacitance increases 2.53 fold (380 to 963 F g⁻¹ at 5 A g⁻¹) due to the synergy of capacitive and faradaic energy storage mechanisms. In the hybrid electrolyte, a SHAC electrode-embedded symmetric SC (SSC) offers a high cycling stability (97%) with 1.6 V wide operational voltage and permits energy storage and power density higher than those reported so far for aqueous electrolyte-based SSCs and asymmetric SCs. In addition, these SSCs provide long-lasting operational capabilities that are useful for driving various portable electronic devices. The obtained results demonstrate a feasible methodology to utilize the maximum available surface area of carbonaceous materials for electrochemical energy storage applications.

As a cathode in aqueous zinc-ion capacitors (ZICs), nitrogen-doped carbon with a 2D bimetallic chalcogenide (NbMo₆S₈/NC) was used. The assembled ZIC demonstrated exceptional electrochemical stability and energy efficiency over thousands of charge–discharge cycles.

The CV profiles of transition metal sulphide electrodes on a Cu-wire (a), and (b) capacitive (light to dark: blue and red) and diffusion-controlled (dark: blue and red) contributions of the hybrid Cu@CoS/NiCo₂S₄ and Cu@ZnCo₂S₄ electrodes.