Abstract
This paper presents and compares two different types of screen-printed flexible and conformable pressure sensors arrays. In both variants, the flexible pressure sensors are in the form of segmental arrays of parallel plate structure—sandwiching the piezoelectric polymer polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] between two printed metal layers of silver (Ag) in one case and the piezoresistive [multiwall carbon nanotube (MWCNT) mixed with poly(dimethylsiloxane (PDMS)] layer in the other. Each sensor module consists of $4 \times 4$ sensors array with 1-mm $\times 1$ -mm sensitive area of each sensor. The screen-printed piezoelectric sensors array exploits the change in polarization level of P(VDF-TrFE) to detect dynamic tactile parameter such as contact force. Similarly, the piezoresistive sensors array exploits the change in resistance of the bulk printed layer of MWCNT/PDMS composite. The two variants are compared on the basis of fabrication by printing on plastic substrate, ease of processing and handling of the materials, compatibility of the dissimilar materials in multilayers structure, adhesion, and finally according to the response to the normal compressive forces. The foldable pressure sensors arrays are completely realized using screen-printing technology and are targeted toward realizing low-cost electronic skin.
Highlights
Printed electronics and sensors over large areas and diverse substrates is growing rapidly due to attractive features such as low-cost processing and possibility of depositing diverse materials over nonplanar surfaces
Arrays of all screen printed flexible pressure sensors presented here were obtained by sandwiching P(VDF-TrFE) and multiwall carbon nanotube (MWCNT)/PDMS separately between two patterned silver layers
Based on the physical characteristics of the printed layers, MWCNT/PDMS (3% wt) nanocomposite show uniform patterned deposition and reusability of the solution for subsequent use
Summary
Printed electronics and sensors over large areas and diverse substrates is growing rapidly due to attractive features such as low-cost processing and possibility of depositing diverse materials over nonplanar surfaces. The implication of these studies in humans on robotics is that the tactile skin should comprise of sensors or transducers capable of detecting both the static and dynamic contact events [4] This is the motivation behind investigating both the piezoelectric and piezoresistive sensors in this work. Considering human touch sensing as reference, the tactile sensors should be able to detect dynamic contact forces up to 1 kHz. On practical side, the cost-effectiveness of electronic or tactile skin, especially of the large area skin, plays a major role in its effective use in robotics.
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