Piezoresistive E‐Skin Sensors Produced with Laser Engraved Molds

Abstract

The recent interest of electronic skin (e‐skin) has pushed the research toward the development of flexible sensors, namely, for pressure detection. Several mechanisms can be used to transduce pressure into electrical signals, but piezoresistivity presents advantages due to its simplicity. The microstructuration of the films composing these sensors is a common strategy to improve their sensitivity. As an alternative to conventional and expensive photolithography techniques and low customizable techniques based on natural molds, a novel strategy for the microstructuration of polydimethylsiloxane (PDMS) films is proposed, based on molds fabricated by laser engraving. After design optimization of these microstructured films, which relies on microcones, piezoresistive sensors with a limit of detection of 15 Pa and a sensitivity of −2.5 kPa−1 in the low‐pressure regime are obtained. These sensors are used with success on the detection of the blood pressure wave at the wrist, thus exhibiting a great potential for health applications.

Piezocapacitive Flexible E‐Skin Pressure Sensors Having Magnetically Grown Microstructures

“…Microneedles of 1:1 sample (minimum MPs' concentration) exhibit maximum aspect ratio out of all, with a percentage increase of 58.18%, when B curing is increased from 135 to 170 mT. It is to be worth mentioning that other researchers have previously attained aspect ratio 0.5–2 by using complex and expensive techniques but we have attained a much larger aspect ratio of 2.61, in a very cost‐effective way …”

“…Especially communication of home service robots and artificial limbs with human beings is carried out via friendly human–machine interaction . An ideal e‐skin is expected to be highly flexible, sensitive, lightweight, easy to fabricate, inexpensive, and should be capable of performing like the natural skin, which feels tactile pressures ranging from light touches (0–10 kPa) to object handling levels (10–100 kPa) . Generally, e‐skin pressure sensors use piezoresistive, piezocapacitive, piezoelectric, and triboelectric sensing mechanisms to transduce applied pressure into an electrical signal.…”

“…Manufacturing of microstructured dielectric films often require molds, which are produced either from certain natural materials or from complicated photolithography and chemical etching processes . Natural‐material‐based molds produce microstructures of specific dimensions while other processes involve multisteps: casting, degassing, vacuum annealing, and peeling of PDMS film, which are not ideal for low cost and large‐area manufacturing .…”

Flexible Broad‐Range Pressure Sensors Enabled by Deformation‐Induced Conductive Channels in 3D Graphene Foam@Polydimethylsiloxane Composite for Precise Vibrational Signal Detection

“…[ 1‐3 ] However, the large‐scale fabrication of pressure sensors with these semiconductor techniques is expensive and complicated, especially in the case of broad‐range deformation detection. To conquer these limitations, several high efficiency and scalability methods are developed, such as, laser micro‐engineering, [ 4‐6 ] UV interface processing, [ 7 ] template‐duplication, [ 8 ] 3D printing. [ 9 ] Besides these newly developed techniques, flexible and malleable pressure sensors with non‐fragile materials also hold great promise to overcome these problems.…”

Flexible and Highly Sensitive Pressure Sensors with Surface Discrete Microdomes Made from Self‐Assembled Polymer Microspheres Array

“…[ 14–17 ] Even though various approaches have been investigated to fabricate flexible pressure sensors and improve their performance, several parameters still need to be improved. To date, various flexible materials and microstructures have been continually developed, such as flexible organic transistors, [ 18 ] pressure sensors, [ 19–25 ] integrated circuits, [ 26 ] stretchable electrodes, [ 27 ] and artificial skins. [ 28–30 ] To fulfill the demand for wearable and flexible devices, flexible pressure sensors are usually required to be worn on nonplanar area even the human body.…”