Wavelength-selective organic field-effect phototransistors based on dye-doped poly-3-hexylthiophene Applied Physics Letters 89, 092110 (2006) We report a tactile touch sensor based on a planar liquid crystal-gated-organic fieldeffect transistor (LC-g-OFET) structure. The LC-g-OFET touch sensors were fabricated by forming the 10 μm thick LC layer (4-cyano-4 -pentylbiphenyl -5CB) on top of the 50 nm thick channel layer (poly(3-hexylthiophene) -P3HT) that is coated on the in-plane aligned drain/source/gate electrodes (indium-tin oxide -ITO). As an external physical stimulation to examine the tactile touch performance, a weak nitrogen flow (83.3 μl/s) was employed to stimulate the LC layer of the touch device. The LC-g-OFET device exhibited p-type transistor characteristics with a hole mobility of 1.5 cm 2 /Vs, but no sensing current by the nitrogen flow touch was measured at sufficiently high drain (V D ) and gate (V G ) voltages. However, a clear sensing current signal was detected at lower voltages, which was quite sensitive to the combination of V D and V G . The best voltage combination was V D = −0.2 V and V G = −1 V for the highest ratio of signal currents to base currents (i.e., signal-to-noise ratio). The change in the LC alignment upon the nitrogen flow touch was assigned as the mechanism for the present LC-g-OFET touch sensors. C 2014 Author(s)