A Study on Materials and Technologies for the Development of Pressure, Temperature, and Humidity Sensors for Electronic Skins

Advances in flexible electronics and smart sensing are bringing electronic skins closer to their biological counterpart than ever before. This demands the integration of state-of-the-art materials, additive manufacturing, and optimized sensor architecture. Therefore, this work focused on developing flexible and printed pressure, temperature, and humidity sensors for potential integration into electronic skins. The MWCNT/PDMS pressure sensor developed in this work enabled fast, sensitive, and continuous pressure monitoring across a range of 1 kPa to 160 kPa, with heightened sensitivity at lower pressure (up to 8.0 %. kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>). The carbon ink-based temperature sensor presented a fast response and a linear temperature dependency of 1.25 %.C<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, from 20 °C to 70 °C. Finally, the humidity sensor, made from a carbon black/cellulose nanofiber composite, was sensitive from 20% to 90 % of relative humidity (RH), and presented three zones of linearity, with a maximum sensitivity of 0.26 %.RH<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>• This study concluded that the developed sensors met the operational requirements of electronic skins and, as a proof-of-concept, a 9-sensor array (comprising 3 sensors of each type) was developed.