Abstract
The search for a piezoelectric elastomer that generates an electrical signal when pressed and stretched has increased significantly in the last decade as they hold great promise in harvesting energy from human motion and monitoring human activities. Here, the excellent elasticity of polydimethylsiloxane-based elastomers and the piezoelectric properties of lead zirconate titanate (PZT) were combined and, using a thermally activated poling process, elastic piezoelectric composites were obtained. For this, two polydimethylsiloxane (PDMS) matrices with a molar mass of 139 kDa and 692 kDa and PZT fillers with particle sizes of 2 and 20 μm were used. For the same poling conditions, an increase in the piezoelectric response with increasing amount of filler, filler size and molar mass of the polymer matrix was observed. Overall, d*33 and d*31 values of 2.7–40 pC N−1 and 16–48 pC N−1 were achieved in this work with filler contents ranging from 37–72 vol%. A composite material with a PZT filler content of 38 vol% (20 μm particle size) in a commercially available PDMS with a Mw = 139 kg mol−1 exhibited high flexibility, good elasticity with long-term mechanical stretchability and high longitudinal and transverse piezoelectric coefficients of 3.6 pC N−1 and 30 pC N−1, respectively. The higher transverse piezoelectric constant d*31 can be explained by an additional capacitor effect of the composite film structure. These properties are interesting features for energy conversion from human motion, monitoring human activities, and stretchable electronics. The functionality of the newly developed material is demonstrated in a pressed sensor.
Highlights
Piezoelectric materials have the characteristic of generating an electrical signal by an induced mechanical stress and vice versa, described by the converse and direct piezoelectric effect
Such composites can undergo high deformation strain, which is an interesting feature for energy conversion from human motion, monitoring human activities and stretchable electronics [16,17,18]
We demonstrated that the longitudinal piezoelectric effect of the prepared composite materials can be utilized to construct a working prototype sensor
Summary
Piezoelectric materials have the characteristic of generating an electrical signal by an induced mechanical stress and vice versa, described by the converse and direct piezoelectric effect. To obtain a piezoelectric effect in a ferroelectric ceramic with randomly distributed grains, the polarization within different grains must be ori ented as much as possible in the same direction This can be achieved by subjecting the ferroelectric materials to a strong electric field via a so-called poling process, where it is assumed that the microscopic polar domains within the crystal structure are reoriented and a permanent polarization is introduced in the macroscopic sample, leading to a high piezoelectric response of the poled material. In order to achieve elasticity, ceramic particles can be dispersed in an elastic matrix such as PDMS, leading to mechanically stable materials Such composites can undergo high deformation strain, which is an interesting feature for energy conversion from human motion, monitoring human activities and stretchable electronics [16,17,18]. Implantable piezoelectric biomedical devices which were powered by motions in the human body such as breath and heartbeat into electrical energy were developed which could pave the way for sustainable future health care technologies [19,20,21]
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