Ionic Signal Amplification Actuated by Gas Dissolution

An array of ionic diodes is fabricated for amplifying ion signals by utilizing gas dissolution. The gases dissolve in the liquid present in the microfluidic device in a localized and convenient manner. To fabricate nanoporous membranes with asymmetric charge properties, pervaporation-assisted particle assembly is employed. A gas-permeable ~10 µm-thick film is utilized to provide structural support while also allowing for gas dissolution. The controllability of the ionic diodes is based on the pH dependence of the particle surface. CO
2
and NH
3
gases are introduced to lower or increase the pH of fluids within the nanoporous membrane.