Flexible liquid metal-based microfluidic strain sensors with fractal-designed microchannels for monitoring human motion and physiological signals.

With the rapid advancement of wearable electronics, there is an increasing demand for high-performance flexible strain sensors. In this work, a flexible strain sensor based on liquid metal (LM)-integrated into a microfluidic device is developed with Peano-type fractal structure design. Compared with the microfluidic sensors with straight and wavy microchannels, the sensor with Peano-shaped channels shows lower hysteresis and improved stretchability. Furthermore, the increase of the fractal order can further improve the sensing performances. The third-order Peano sensor exhibits excellent mechanical and electrical properties, including high tensile capability (490.3%), minimal hysteresis (DH = 0.86%), ultra-low detection limit (0.1%), low overshoot, rapid response time (117 ms), as well as good stability and durability. By adding two independent and perpendicular straight channels to the Peano sensing unit, the feasibility of multi-directional strain recognition is demonstrated. To further improve the sensitivity of the Peano-shaped sensor, a multi-layer Peano sensor is developed, exhibiting remarkably enhanced sensitivity while maintaining low hysteresis. Overall, the developed LM-based microfluidic strain sensors enrolling Peano fractal geometry hold high potential for various wearable electronics applications.

Phase Change Material-Embedded Multifunctional Janus Nanofiber Dressing with Directional Moisture Transport, Controlled Release of Anti-Inflammatory Drugs, and Synergistic Antibacterial Properties.

Wound healing is a systematic and complex process that involves various intrinsic and extrinsic factors affecting different stages of wound repair. Therefore, multifunctional wound dressings that can modulate these factors to promote wound healing are in high demand. In this work, a multifunctional Janus electrospinning nanofiber dressing with antibacterial and anti-inflammatory properties, controlled release of drugs, and unidirectional water transport was prepared by depositing coaxial nanofibers on a hydrophilic poly(ε-caprolactone)@polydopamine-ε-polyl-lysine (PCL@PDA-ε-PL) nanofiber membrane. The coaxial nanofiber was loaded with the phase change material lauric acid (LA) in the shell layer and anti-inflammatory ibuprofen (IBU) in the core layer. Among them, LA with a melting point of 43 °C served as a phase change material to control the release of IBU. The phase transition of LA was induced by near-infrared (NIR) irradiation that triggered the photothermal properties of PDA. Moreover, the Janus nanofiber dressing exhibited synergistic antimicrobial properties for Escherichia coli and Staphylococcus aureus due to the photothermal properties of PDA and antibacterial ε-PL. The prepared Janus nanofiber dressing also exhibited anti-inflammatory activity and biocompatibility. In addition, the Janus nanofiber dressing had asymmetric wettability that enabled directional water transport, thereby draining excessive wound exudate. The water vapor transmission test indicated that the Janus nanofiber dressing had good air permeability. Finally, skin wound healing evaluation in rats confirmed its efficacy in promoting wound healing. Therefore, this strategy of designing and manufacturing a multifunctional Janus nanofiber dressing had great potential in wound healing applications.