Abstract
Ultrasensitive flexible sensors with multi-sensing functions are required for various applications in flexible electronics era. Here we demonstrate flexible polymer-dispersed liquid crystal (PDLC)-integrated-organic field-effect transistors (OFETs) (PDLC-i-OFETs), which sensitively respond to various stimulations including weak gas (air) flow, direct physical touch, light, and heat. The flexible PDLC-i-OFETs were fabricated by spin-coating the poly(methyl methacrylate) (PMMA)-dispersed 4,4’-pentyl-cyanobiphenyl (5CB) layers on the poly(3-hexylthiophene) (P3HT) channel layers of OFETs with 200 μm-thick poly(ethylene naphthalate) (PEN) substrates. The flexible PDLC-i-OFET devices could sense very weak nitrogen gas flow (0.3 sccm), which cannot be felt by human skins, and stably responded to direct physical touches (0.6~4.8 g load). In addition, the present devices showed very sensitive photoresponses to a visible light and exhibited excellent heat-sensing characteristics at a temperature of 25~70 °C. In particular, the present flexible PDLC-i-OFET devices could sense two different stimulations at the same time, indicative of promising multi-sensing capabilities.
Highlights
On this account, ultrasensitive tactile sensors have been developed by combining organic field-effect transistors (OFETs) and liquid crystals (LCs) for possible applications to artificial skins of humanoid robots and wearable e-gloves or e-clothes etc[28,29,30,31,32,33]
We report multi-functional flexible PDLC-integrated-OFET (PDLC-i-OFET) sensors via successful preparation of stable solid-state LC sensing layers based on the concept of polymer-dispersed liquid crystal (PDLC)
The PLDC sensing layers were prepared by embedding 4,4′-pentyl-cyanobiphenyl (5CB) micro-dots in the poly(methyl methacrylate) (PMMA) matrix, which were integrated on the flexible OFETs with 200 μm-thick poly(ethylene naphthalate) (PEN) substrates
Summary
Ultrasensitive tactile sensors have been developed by combining OFETs and liquid crystals (LCs) for possible applications to artificial skins of humanoid robots and wearable e-gloves or e-clothes etc[28,29,30,31,32,33]. The previous LC-i-OFET sensors have a drawback in terms of practical applications owing to the fully liquid state of LC in the sensing layers. No multi-functional sensing approach has been tried with the previous LC-i-OFET sensors. We report multi-functional flexible PDLC-integrated-OFET (PDLC-i-OFET) sensors via successful preparation of stable solid-state LC sensing layers based on the concept of polymer-dispersed liquid crystal (PDLC). The PLDC sensing layers were prepared by embedding 4,4′-pentyl-cyanobiphenyl (5CB) micro-dots in the poly(methyl methacrylate) (PMMA) matrix, which were integrated on the flexible OFETs with 200 μm-thick poly(ethylene naphthalate) (PEN) substrates. The fabricated PDLC-i-OFET devices were able to sense four different objects such as weak air (gas) flow, strong physical force (touch), light, and heat
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