Nature-Driven Biocompatible Epidermal Electronic Skin for Real-Time Wireless Monitoring of Human Physiological Signals.

Wearable bioelectronic patches are creating a transformative effect in the health care industry for human physiological signal monitoring. However, the use of such patches is restricted due to the unavailability of a proper power source. Ideal biodevices should be thin, soft, robust, energy-efficient, and biocompatible. Here, we report development of a flexible, lightweight, and biocompatible electronic skin-cum-portable power source for wearable bioelectronics by using a processed chicken feather fiber. The device is fabricated with a novel, breathable composite of biowaste chicken feather and organic poly(vinylidene fluoride) (PVDF) polymer, where the chicken feather fiber constitutes the "microbones" of the PVDF, enhancing its piezoelectric phase content, biocompatibility, and crystallinity. Thanks to its outstanding pressure sensitivity, the fabricated electronic skin is used for the monitoring of different human physiological signals such as body motion, finger and joint bending, throat activities, and pulse rate with excellent sensitivity. A wireless system is developed to remotely receive the different physiological signals as captured by the electronic skin. We also explore the capabilities of the device as a power source for other small electronics. The piezoelectric energy harvesting device can harvest a maximum output voltage of ∼28 V and an area power density of 1.4 µW·cm-2 from the human finger imparting. The improved energy harvesting property of the device is related to the induced higher fraction of the electroactive phase in the composite. The easy process ability, natural biocompatibility, superior piezoelectric performance, high pressure sensitivity, and alignment toward wireless transmission of the captured data make the device a promising candidate for wearable bioelectronic patches and power sources.

Ultraviolet- and Microwave-Protecting, Self-Cleaning e-Skin for Efficient Energy Harvesting and Tactile Mechanosensing.

Smart, self-powered, and wearable e-skin that mimics the pressure sensing property of the human skin is indispensable to boost up cutting edge robotics, artificial intelligence, prosthesis, and health-care monitoring technologies. Here, fabrication of a facile and flexible hybrid piezoelectric e-skin (HPES) with multifunctions of tactile mechanosensing, energy harvesting, self-cleaning, ultraviolet (UV)-protecting, and microwave shielding properties is reported. The principal block of the HPES is an SnO2 nanosheets@SiO2 (silica-encapsulated tin oxide nanosheets)/poly(vinylidene fluoride) (PVDF) nanocomposite (SS)-based PES acting as a single unit for simultaneous energy harvesting and tactile mechanosensing. Gentle human finger imparting onto the PES showed outstanding energy conversion efficiency (16.7%) with high power density (550 W·m-3) and current density (0.40 µA·cm-2). This device can generate high enough electrical power to directly drive portable electronics like a light-emitting diode (LED) panel (consisting of 85 commercial LEDs) and to charge up capacitors very rapidly. Thin PES mechanosensors demonstrated promising performance for quantitatively detecting static and dynamic pressure stimuli with a high sensitivity of 0.99 V·kPa-1 and a short response time of 1 ms. PES was also integrated to a health-data glove for precisely monitoring and discriminating fine motions of proximal interphalangeal, metacarpophalangeal, and distal interphalangeal joints of a human finger and bending motion of different human fingers. A (4 × 4) sensing matrix of PES was successfully employed to detect the spatial distribution of static pressure stimuli. The sensing matrix can precisely record the shape and size of an object placed onto it. PES was encapsulated with a nanocomposite film for providing self-cleaning and UV and microwave protection capability to the HPES. The hydrophobic SS film wrapping (water drop contact angle ∼85.6°) of the HPES enables the self-cleaning feature and makes HPES resistive against water and dirt. The HPES was integrated with in-house-made robotic hands, and the responses of the sensors due to grabbing of an object were evaluated. This work explores new prospects for UV- and microwave-protective, self-cleaning e-skin for energy harvesting and mechanosensation, which can eventually boost up the self-powered electronics, robotics, real-time health-care monitoring, and artificial intelligence technologies.

Enhancement of electroactive ß phase crystallization and dielectric constant of PVDF by incorporating GeO2 and SiO2 nanoparticles.

Poly(vinylidene fluoride) (PVDF) nanocomposites are recently gaining importance due to their unique dielectric and electroactive responses. In this study, GeO2 nanoparticles/PVDF and SiO2 nanoparticles/PVDF nanocomposite films were prepared by a simple solution casting technique. The surface morphology and structural properties of the as-prepared films were studied by X-ray diffraction, scanning electron microscopy, and FT-IR spectroscopy techniques. The studies reveal that the incorporation of GeO2 or SiO2 nanoparticles leads to an enhancement in the electroactive ß phase fraction of PVDF due to the strong interactions between the negatively charged nanoparticle surface and polymer. Analysis of the thermal properties of the as-prepared samples also supports the increment of the ß phase fraction in PVDF. Variation of dielectric constant, dielectric loss, and ac conductivity with frequency and loading fraction of the nanoparticles were also studied for all the as-prepared films. Dielectric constant of the nanocomposite films increases with increasing nanofiller concentration in PVDF. 15 mass% SiO2-loaded PVDF film shows the highest dielectric constant, which can be attributed to the smaller size of SiO2 nanoparticles and the homogeneous and discrete dispersion of SiO2 nanoparticles in PVDF matrix.