Recently, there has been a lot of research on electricity generation with motion of a water droplet on hydrophobic material coated electrodes. One of the origins of electricity generation on the transducers is assumed that the ion adsorption/desorption phenomena, which are induced by motion of a water droplet. The adsorbed ions attract or push the electrons in the electrodes, resulting in output signals. Generally, cations in the ionic water are adsorbed on the hydrophobic surface when the contact area between the ionic water droplet and the surface increases. Because it uses material which has high negative charge for hydrophobic layer such as Teflon or self-assembled monolayer of fluorinated silane (F-SAM) in the most of previous works.<br/>Here, we demonstrated electricity generation by motion of an water droplet on a mixed SAMs based active transducer(MSAT) which has the reversal electrical properties compared with a F-SAM based active transducer(FAT). Specifically, a comparison of the electrical properties in the FAT and the MSAT with various concentration of alkaline metal and halide ions were investigated in this work. The mixed SAMs are composed of APTES (3-Aminopropyltriethoxysilane) and fluorinated silane. In case of the FAT, the measured output voltage and peak power were ~1 V and 0.11 μW with the 30 μl of 0.01M NaCl. Whereas, in case of the MSAT, the measured output voltage and peak power were ~ -1 V and 0.12 μW with the same conditions. Moreover, we found a re-inversion phenomenon of output voltage in a certain ion concentration or more. We believe that a functional group of NH3<sup>+ </sup>which has a positive charge in the mixed SAMs is dominant factor of the reversed properties and the re-inversion phenomenon. Based on these properties, we verified the possibility of a self-powered pH sensor in various concentration of acid and base solutions.

Control of electrical properties by mixed self-assembled monolayers in a water motion active transducer

253rd National Meeting (2017)

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