A review on flexible gas sensors: From materials to devices

This review discusses the recent developments of flexible chemiresistive gas sensors, focusing on the main materials and fabrication techniques. This article provides a detailed description of the substrates used in the flexible gas sensing industry. It also highlights the main challenges faced when integrating a sensing layer on paper, textile or polymeric substrates. A detailed study of the sensing materials in terms of structural properties and sensing mechanisms is presented. This study uses examples of gas sensors to explain the sensing mechanisms and to emphasize the functionalization effect on the sensing performance of a material. It also highlights the exceptions in polymers sensing behavior. Since flexible substrates can’t sustain high temperatures, the main techniques used to fabricate flexible gas sensors are explained such as coating, printing, physical vapor deposition, in situ-growth, in situ-polymerization and chemical vapor deposition. The last technique, which requires high temperatures, is mostly used prior to transferring a sensing layer to a flexible substrate. At the end, the main challenges facing the flexible gas sensing technology are pointed out.