Effects of applied voltage waveform on the uniformity of a microplasma array confined inside polydimethylsiloxane microchannels

The uniformity of the microplasma array is essential to modify the hydrophilicity of the inner surface of polydimethylsiloxane (PDMS) microchannels by plasma treatment. In this study, the effects of applied voltage waveforms on the uniformity of the microplasma array are investigated. Interestingly, the microplasma array excited by AC (alternate current) voltage looks more uniform by a digital camera and has higher gas temperature and electron density than that excited by unipolar and bipolar pulse voltage. Imaging the microplasma array by a fast intensified charge-coupled device camera shows that the ignition of microplasma inside each microchannel has strong randomness in spatial distribution, and the opportunity of each microchannel being ignited is almost equal. Detailed analysis reveals that the low density of surface charges and the small overvoltage in the case of AC voltage are expected to play crucial roles in the stochastic behavior of microplasma ignition inside PDMS microchannels. This study is useful for understanding the uniformity of the microplasma array for surface modification of PDMS microchannels.

Automated summary

This study investigates the effects of different voltage waveforms on the uniformity of the microplasma array for modifying the hydrophilicity of PDMS microchannels. The microplasma array excited by AC voltage appears more uniform and has higher gas temperature and electron density. The ignition of microplasma inside each microchannel shows strong randomness in spatial distribution, with nearly equal opportunities for each microchannel to be ignited.