We report on the fabrication of an ultra-high aspect ratio ionically conductive single microchannel with tunable diameter from ≈ 20 μm to fully closed. The 4 mm-long channel is fabricated in a Polydimethylsiloxane (PDMS) mold and its cross-sectional area is controlled by applying macroscopic compressive strain to the mold in a direction perpendicular to the channel length. We investigated the ionic conduction properties of the channel. For a wide range of compressive strain up to ≈ 0.27, the strain dependence of the resistance is monotonic and fully reversible. For strain > 0.27, ionic conduction suddenly shuts off and the system becomes hysteretic (whereby a finite strain reduction is required to reopen the channel). Upon unloading, the original behavior is retrieved. This reversible behavior is observed over 200 compression cycles. The cross-sectional area of the channel can be inferred from the ion current measurement, as confirmed by a Nano-Computed Tomography investigation. We show that the cross-sectional area decreases monotonically with the applied compressive strain in the reversible range, in qualitative agreement with linear elasticity theory. We find that the shut-off strain is affected by the spatial extent of the applied strain, which provides additional tunability. Our tunable channel is well-suited for multiple applications in micro/nano-fluidic devices.
Macroscopic strain controlled ion current in an elastomeric microchannel
Chin-Chang Kuo, Yongxue Li, Du Nguyen, Steven Buchsbaum, Laura Innes, Aaron P. Esser-Kahn, Lorenzo Valdevit, Lizhi Sun, Zuzanna Siwy, Michael Dennin; Macroscopic strain controlled ion current in an elastomeric microchannel. J. Appl. Phys. 7 May 2015; 117 (17): 174904. https://doi.org/10.1063/1.4919353
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