Large area and flexible micro-porous piezoelectric materials for soft robotic skin

Abstract

The need for flexible, highly sensitive tactile sensors that can fit onto curved surfaces is driving the conformable sensor materials research in the field of Human-Machine Interactions. Here we report a new type of compliant piezoelectric active composite, a micro-porous polyurethane-PZT material, capable of generating a voltage output upon touch. The composites are synthesized with the aim of maximizing the piezoelectric sensitivity of particulate composite sensor materials. The goal is to reduce the dielectric constant of the polymer matrix and improve flexibility of conventional bulk piezo-composites, consisting of ceramic particles in a dense polymeric matrix, by adding a third (gaseous) phase to the system in the form of uniformly sized pores. The presence of the gaseous component in the polymer matrix in the form of well-distributed spherical inclusions effectively decreases the polymer dielectric permittivity, which increases the piezoelectric voltage sensitivity (g 33) of the composite sensors significantly. The unique combination of dielectrophoretic structuring of PZT particles and the addition of a gaseous phase to the polymer resin results in the highest performance of the particulate composite sensors reported in the literature so far. The newly developed micro-porous composites show g 33 value of 165 mV.m/N that is twice that of the structured PZT-bulk PU composites (80 mV.m/N) and more than five times the g 33 value of bulk PZT ceramics (24-28 mV.m/N). The capability of the flexible freestanding sensors for application in touch sensing devices for soft robotics is demonstrated.

Flexible Multiscale Pore Hybrid Self-Powered Sensor for Heart Sound Detection

“…Rybyanets et al proposed that, compared with the dense film, porous piezoelectric materials have better hydrostatic performance and their acoustic impedance is low, so by introducing controllable pores, the acoustic performance and ultrasonic response can be significantly improved [ 23 ]. Khanbareh et al prepared a porous PZT–PU composite structure with a piezoelectric coefficient of 165 mV/N through the chemical reaction of water and polyurethane (PU) [ 24 ]. Moreover, porous electrets are a kind of flexible material showing excellent features of ferroelectricity after corona poling [ 25 ].…”

A self-power flexible piezoelectric sensing system for badminton training monitoring

“…Among which the piezoelectric transducers can achieve compact and highefficient detection of the physical pressure [12,13] compared with the electromagnetic and triboelectric types. More importantly, recent advances in material synthesis provide a promising option to develop soft piezoelectric devices [14,15], which can make it suitable for flexible and mechanically stretchable hitting system [16,17], such as badminton racket and tennis racket. Even though the hard contact sensing towards table tennis training has been reported by Tian et al [18].…”

Highly-Loaded Thermoplastic Polyurethane/Lead Zirconate Titanate Composite Foams with Low Permittivity Fabricated using Expandable Microspheres

“…In the past, several methods have attempted to enhance the sensing efficiency of piezocomposites [23,24,25,26]. The introduction of cellular structure to piezocomposites can result in a decreased permittivity ( ε ) [27,28,29,30]. As reported in the work of [31], the introduction of cellular structure will not affect the overall value of d , and thus the decreased permittivity should enhance the sensing capability ( g ).…”

“…Very limited work, however, has been reported on the foaming of piezocomposites. Recently, De Boom et al [ 27 ] and Khanbareh et al [ 28 , 29 ] reported polyurethane/PZT composite foams prepared using magnetic stirring and the whipped cream maker method. McCall et al [ 30 ] worked on polydimethylsiloxane (PDMS)/BTO/multiwalled carbon nanotube (MWCNT) composites and foamed them via the sugar-templating method.…”