Soft, Super-Elastic, All-Polymer Piezoelectric Elastomer for Artificial Electronic Skin

Abstract

Piezoelectric sensors are widely used in wearable devices to mimic the functions of human skin. However, it is considerably challenging to develop soft piezoelectric materials that can exhibit high sensitivity, stretchability, super elasticity, and suitable modulus. In this study, a soft skin-like piezoelectric polymer elastomer composed of poly(vinylidene fluoride) (PVDF) and a novel elastic substrate polyacrylonitrile is prepared by combining the radical polymerization and freeze-drying processes. Dipole−dipole interaction results in the phase transition of PVDF (α phase to β phase), which enhances the electrical and mechanical performances. Thus, we achieve a high piezoelectric coefficient (d 33max = 63 pC/N), good stretchability (211.3−259.3%), super compressibility (subjected to 99% compression strain without cracking), and super elasticity (100% recovery after extreme compression) simultaneously for the elastomer. The soft composite elastomer produces excellent electrical signal output (V ocmax = 253 mV) and responds rapidly (15 ms) to stress-induced polarization effects. In addition, the elastomer-based sensor accurately detects various physiological signals such as gestures, throat vibrations, and pulse waves. The developed elastomers exhibit excellent mechanical properties and high sensitivity, which helps facilitate their application as artificial electronic skin to sense subtle external pressure in real time.

All-Polymer Piezoelectric Elastomer with High Stretchability, Low Hysteresis, Self-Adhesion, and UV-Blocking as Flexible Sensor

“…As shown in Figure S23b, the capacitor was charged for about 60 s and then discharged for 10 s for four cycles. Finally, the prepared piezoelectric elastomer sensors were compared with previously reported elastomer sensors in terms of stretchability, self-powering, adhesion, compressibility, biocompatibility, and UV-blocking performances (Figure i), ,,− demonstrating the superior properties of the PPO elastomer and great potential in human activity monitoring, personal healthcare diagnosis, and Morse code communication.…”

“…Therefore, the maximum output voltage of approximately 237 mV was obtained when OTA weight ratio was 5 wt %. However, the voltage of the PPO 7 elastomer remained basically unchanged, given that the number of dipoles in the elastomer was limited to generate higher voltage . Then, we tested the output voltage generated from the PPO 5 elastomer by increasing the loading pressure from 2.64 to 33.07 kPa, as shown in Figure b.…”

“…However, the voltage of the PPO 7 elastomer remained basically unchanged, given that the number of dipoles in the elastomer was limited to generate higher voltage. 47 Then, we tested the output voltage generated from the PPO 5 elastomer by increasing the loading pressure from 2.64 to 33.07 kPa, as shown in Figure 5b. As the exerted pressure increased, the generated output voltage increased and finally saturated at 33.07 kPa; this can be explained by the fact of crystal deformation of the polymer.…”

Recent Advance in Stretchable Self‐Powered Piezoelectric Sensors: Trends, Challenges, and Solutions

“…The soft mechanical properties of elastomer (good flexibility, high elasticity and satisfied mechanical performance) make it suitable as the energy dissipating phase, thus enabling devices stretchable for conformal integration with human bodies. Common strategies include developing intrinsically piezoelectric elastomer, [52][53][54] piezoelectric polymer/elastomer blend, [55][56][57] elastomer composites with piezoelectric fillers, [58][59][60][61] and stretchable structural designs (wavy geometries, serpentine patterns, and kirigami layouts and textile structures, etc.) combined with elastomeric phase as binders, [62] substrates [63][64][65] or/and encapsulating materials.…”

Polyelectrolyte Hydrogel with Piezoelectricity and Adhesion for Soft Electronics

“…Currently, there are three main types of self-powered hydrogels: hydrogel-based triboelectric nanogenerators (based on the coupling of triboelectric effects), 12,13 piezoionic hydrogel (based on the directional movement of ions in response to pressure), 14 and piezoelectric hydrogel (based on the piezoelectric effect). 15,16 The hydrogel-based triboelectric nanogenerators have excellent electrical performance and strong signal, but large impedance, complex preparation process, difficulty, and high cost, which is not conducive to large-scale production. 17−20 The piezoionic hydrogels are easy to prepare, but ion leakage and instability limit further development.…”