Abstract
The low stretchability of plain membranes restricts the sensitivity of conventional diaphragm-based pressure and inflatable piezoelectric sensors. Using theoretical and computational tools, we characterized current limitations and explored metamaterial-inspired membranes (MetaMems) to resolve these issues. This paper develops two MetaMem pressure sensors (MPSs) to enrich the sensitivity and stretchability of the conventional sensors. Two auxetic hexagonal and kirigami honeycombs are proposed to create a negative Poisson’s ratio (NPR) in the MetaMems which enables them to expand the piezo-element of sensors in both longitudinal and transverse directions much better, and consequently provides the MPSs’ diaphragm a higher capability for flexural deformation. Polyvinylidene fluoride (PVDF) and polycarbonate (PC) are considered as the preferable materials for the piezo-element and MetaMem, respectively. A finite element analysis was conducted to investigate the stretchability behavior of the MetaMems and study its effect on the PVDF’s polarization and sensor sensitivity. The results obtained from theoretical analysis and numerical simulations demonstrate that the proposed MetaMems enhance the sensitivity of pressure sensors up to 3.8 times more than an equivalent conventional sensor with a plain membrane. This paper introduces a new class of flexible MetaMems to advance wearable piezoelectric metasensor technologies.
Highlights
Sometimes, conventional piezoelectric sensors have sensitivity limitations, owing to their intrinsic lack of stretchability [1–4]
To predict a magnification factor for the proposed MetaMem pressure sensors (MPSs), their sensitivity was investigated for different excitation frequencies and amplitudes in which the thin diaphragm film of the substrate was subjected to a bending movement caused by a harmonic pressure of 1 to 10 kPa at a frequency range of 1648 (Hz) to 2472 (Hz)
The results showed that the MPSs with the MetaMem generated more voltage compared to the conventional pressure sensors (CPSs) with the plain membrane
Summary
Conventional piezoelectric sensors have sensitivity limitations, owing to their intrinsic lack of stretchability [1–4]. In order to enhance stretchability and mechanical compliance, metamaterial-inspired substrates for piezoelectric devices are rapidly growing and becoming widespread [5,6]. Poisson’s ratio defines the ratio between two characteristics of the transverse and longitudinal strain of a structure, and NPR behavior has been discovered in auxetic materials that expand (contract) in the transverse direction when stretched (compressed), instead of usual materials (Figure 1) [10–14]. Such an auxetic behavior is found in some hexagonal [15–20] and kirigami honeycombs [21–27]. Auxeticinspired designs for flexible membranes and substrates are attracting growing attention in developing the generation of highly efficient piezoelectric sensors and harvesters
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