(364a) Stochastic Pore Blocking and Gating in PDMS Nanopores Due to Liquid-Vapor Phase Transitions

Polydimethylsiloxane (PDMS) is a versatile polymer that has long been used as an impermeable barrier for microfluidic and other devices. Herein we report an unusual phenomenon observed when patch clamp is performed on a grooved and flat PDMS surface, resulting in stochastic current fluctuations that are due to a nanopore being formed by the PDMS. Experiments demonstrate the pores are deformable and that the majority charge carriers are from the electrolyte. Furthermore, comparison of ionic and nonionic surfactants gives a bracketed pore size of roughly 2-10 nm. The mechanism of stochastic pore-blocking was attributed to a liquid-vapor phase transition which has been proposed in other nanopore experiments and simulations, which we support by showing a dwell time distribution that does not change significantly with voltage, indicating an uncharged blocker. Experimental residence time ratios and pore-blocking currents are compared with an ionic capillary evaporation model proposed by Palmeri et al.¹ which further confirm phase transitions as the cause of pore-blocking. These experiments demonstrate a very simple platform for studying nanopores and stochastic transport caused by phase transitions occurring inside the nanopore.

¹Buyukdagli, S., Manghi, M., & Palmeri, J. (2010). Ionic Capillary Evaporation in Weakly Charged Nanopores. Physical Review Letters, 105(15), 1-4.