NiO@SiO₂/PVDF: A Flexible Polymer Nanocomposite for a High Performance Human Body Motion-Based Energy Harvester and Tactile e-Skin Mechanosensor

Abstract

Advancement in self-powered portable and wearable electronics mostly depends on the realization of an efficient human activity-based energy harvester and electronic skin (e-skin)-mimicking tactile mechanosensing property of natural human skin. A human activity-based energy harvester can supply power to flexible, potable, electronics equipment associated with the human body, whereas a tactile e-skin mechanosensor can precisely detect static and dynamic pressure stimuli. Here, we report development of a NiO@ SiO 2 /PVDF nanocomposite, a facile piezoelectric material possessing superior flexibility that is light in weight and has low cost, which is an excellent choice for the next generation mechanical energy harvester and tactile e-skin sensors. The fabricated piezoelectric nanogenerator (PNG) comprising nanocomposites shows very promising output under application of the biomechanical force on it. PNG15 exhibits high output voltage (53 V), adequate current density (∼0.3 μA/cm 2 ), high power density (685 W/m 3 ), and superior conversion efficiency (13.86%). Gentle human finger imparting onto the PNG produces enough electric power to directly illuminate as many as 85 numbers of commercial LEDs and charge a 2.2 μF capacitor up to 22 V within 450 s. The nanogenerator is successfully exploited to generate electrical power by converting mechanical energy from different human activities. We also demonstrate the high mechanosensing capability of a thin, flexible e-skin sensor based on NiO@SiO 2 /PVDF nanocomposites. Because of the high sensitivity, the fabricated e-skin sensor can detect precisely the spatiotemporal distribution of pressure stimuli in static and dynamic conditions. The e-skin sensor is capable of sensing very low level pressure stimuli with a short response time. The promising role of e-skin in real time healthcare monitoring is assessed where a hand-data glove attached with self-powered e-skin sensors can distinguish movements of different fingers. The spatial distribution of pressure stimuli is also resolved by a sensing matrix containing e-skin sensors as pixels. Moreover the operation mechanical stability of the composites is very high which enables this composite to be used in e-skin sensor and energy harvester applications. Our work verifies the scope of NiO@SiO 2 /PVDF nanocomposites in nanogenerators and e-skin applications which are essential components in the field of wearable self-powered electronics, healthcare monitoring, and artificial intelligence attached to a human body.

Hybrid lead-free polymer-based nanocomposites with improved piezoelectric response for biomedical energy-harvesting applications: A review

“…Lead-free piezoceramic particles (BT, KNN) [48-51, 54, 55], metal oxide NPs (ZnO, MgO, TiO 2 ) [19,[56][57][58][59], CNTs [60][61][62][63][64][65], graphene and graphene derivatives such as rGO [27,66,67], hydrated ionic salts [68], nanoclays [69,70], and metal NPs (Ag, Pt) [71,72] have all proven to be highly efficient as nucleating fillers that can induce a polar electroactive phase without applying electrical polarization. By optimizing the concentration and uniformity of the distribution of the fillers in the polymer matrix, superior piezoelectricity and dielectric values are obtained.…”

“…The proposed e-skin can also degrade many kinds of organic pollutants and sterilise bacteria on its surface. middle and ring fingers [59], (c) distinguishing the landing moments of legs [202], (d) plantar pressure measurements [203]. Reprinted with the permission from the American Chemical Society…”

“…A hybrid nanocomposite film of silica-coated NiO NPs loaded in PVDF 200 µm in thickness and 1.6×2.5 cm 2 in area was fabricated as a piezoelectric NG and demonstrated e-skin properties [59].…”

“…The first attempt to utilize the synergetic effect of Gr nanosheets and ceramic NPs yielded a high output voltage of ~112 V, but this value is still much lower than the ~200 V obtained using a PZTbased NG under bending deformation [7]. Structuring of the nanofiller particles, such as co-doping and coating, can also be useful for improving the performance of electroactive and bioactive materials [19,45,59,76]. Importantly, only pristine piezopolymers have been tested in vivo as implanted NGs for energy harvesting from the daily activity of living organisms [119,210].…”

“…Loading nanofillers of various shapes and sizes ( Figure S4), including complex doped [19,31,45,55] and coated [59,76,208] fillers, into a piezopolymer matrix can efficiently increase its electroactive properties, while co-doping with several different types of nanofillers and optimising their content [27,209] will provide further improvements in sensitivity. Furthermore, the muchless-explored and -exploited microscale patterning and the alignment of nanofiller particles inside the piezopolymer matrix are significant steps towards tuning and controlling the material properties ( Figure S5).…”