Publications

Research in hybrid electronics has included advances in materials, devices and architectures. However, in practice, controversy still exists on some details which limit hybrid materials to high-performance applications, such as processing–structure–design–property relations. This paper describes a practical approach to enhancing the sensing performance of a prototype ammonia gas sensor based on electrical conductivity changes, percolation theory and current limitation to a semiconducting polymer-metal oxide medium. This device is based on fully-gravure printed polyaniline/indium - tin oxide nanocomposites, Pani100−xITOx [0 ≤ x≤ 100% (wt/wt)], layers on a freestanding high-density polyethylene substrate. We find that the electrical current of the device decreases and tends to saturate as the gas concentration increases, and the value of this electrical current limit (IL) depends on x: the higher the value of x, the smaller the IL, when the current that flows through the electronic device was dominated by the ITO-nanoparticle filled PAni, which increase the concentration of hopping carriers and contribute to the desired electrical response of a heterogeneous gas sensor. In this regime, we find a good linear relationship between x and ammonia concentration. These findings suggest new directions for future research on the development and investigation of organic-inorganic devices in which the electrical current variation is desired for enhanced sensitivity and stability of hybrid sensors.

Ultrasensitive strain sensors have significant practical application in human-motion detection. However, there is still a challenge for developing strain sensors that are capable of detecting high strain and a high gauge factor (GF). The aim of this study was to investigate whether a semiconducting polymer and AC measurements are able to improve the GF of stretchable sensors. We employed complex impedance spectroscopy measurements to adjust the optimal operating frequency and the impedance component for improving the device performance of a polyaniline film on a flexible poly(vinyl chloride):diisononyl phthalate sub-strate. In the DC regime, the sensor revealed linearity and GF ∼18 at 46% strain. oreover, the frequency of 100 Hz corresponds to the ideal work re- gion to operate the device that unifies sensitivity and linearity, as well as to directly correlate GF and Z∗(100) data. The most surprising correlation is with GF from Z”(100), i.e. GF”(100), which is about 9 times higher than GF (DC regime) at 46% strain. The Cole-Davidson approach is developed, in which Z’(f) and Z”(f) are calculated as functions of tensile stress. This model provides the correlation between GF”(100) and the electrical resistance and capacitance of the device, as well as the charge-carrier hopping distance dependence on the tensile stress.