UV‐Printable and Flexible Humidity Sensors Based on Conducting/Insulating Semi‐Interpenetrated Polymer Networks

Abstract

Humidity sensors are of great interest in many fields because humidity plays a crucial role in several processes. Nevertheless, their application is often limited by the expensive fabrication and the stiffness of the substrates usually employed. In this work, novel UV‐curable and flexible humidity sensors based on semi‐interpenetrated polymer networks are fabricated. They can be prepared either as self‐standing sensors or applied on different bendable substrates. The fabrication consists of a simultaneous UV‐curing of an insulating network (acrylic or epoxy) and photopolymerization of conducting polypyrrole (PPy). The detection mechanism involves proton transfer on the PPy chains that can be macroscopically observed by electrical impedance variations. These devices show promising humidity‐sensing properties from 20 to 97% of relative humidity with a maximum response of about 180%. The dynamic sensing investigation proves that the recovery process can be tailored playing on the glass transition temperature and wettability of the films. The remarkable sensing capabilities of these sensors make them a valid alternative in many applications where printability and flexibility are required along with simple fabrication method consisting of one‐step synthesis.

A Flexible, Highly Sensitive, and Selective Chemiresistive Gas Sensor Obtained by In Situ Photopolymerization of an Acrylic Resin in the Presence of MWCNTs

“…In the scientific literature there is a large interest for these sensors where the improvement of sensitivity and selectivity is required . Metal oxide semiconductors, conducting polymers, and composites are among the most commonly utilized materials employed in building these devices. Even if the sensing mechanism is different for the three cited materials, the working principle behind them is always the same.…”

Rubbery Electronics Fully Made of Stretchable Elastomeric Electronic Materials

“…Because structural engineering for stretchable electronics with intrinsically nonstretchable materials has limitations for integration, packaging, and manufacturing cost due to large space usage for interconnection, stretchable electronics based on all rubber‐like components are promising future alternatives. Therefore, many rubbery electronics have been developed including transistors, logic gates, optoelectronic devices, physical sensors, energy harvesting devices, and others …”

“…In addition, the devices presented a low limit of detection of ≈1 ppm with a sensitivity of 1.6% for toluene and operated reliably under harsh environmental conditions (relative humidity, RH, of 85% or temperature of 100 °C) as well as mechanical deformations such as bending (bending to a radius of curvature of 1 mm) and stretching (strain of 100%). The rubbery humidity sensor is also an emerging device . Trung et al developed a transparent, stretchable humidity sensor from a rubber‐like stretchable component .…”

Artificial muscles driven by the cooperative actuation of electrochemical molecular machines. Persistent discrepancies and challenges

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