Implementation of a nanochannel open/close valve into a glass nanofluidic device

In micro-/nanofluidics, channel open/close valves are fundamental to integrating fluid operations and realizing highly integrated analytical devices. Recently, we proposed a nanochannel open/close valve utilizing glass deformation and verified the principle of opening and closing nanochannels. Glass deformation sufficient to close the valve was achieved using a 45-µm-thick glass sheet as a material of a nanofluidic device. However, since the device incorporates the thin glass sheet and is not robust enough to be used for repeated analyses, fluid operations utilizing the valve have not been verified sufficiently. Thus, in the present study, we fabricated a nanofluidic device implemented with a nanochannel open/close valve using rigid glass substrates of thicknesses on the order of 100 μm, and verified fluid operations utilizing the valve. On a small part of the substrate, we designed and fabricated a 30-µm-thick deformation section for the valve. The open/close operation and the performance of the valve were verified. The leakage of the valve was measured to be 2%, the response time was 0.9 s, and the number of repetitions was over 100,000. By utilizing the fabricated valve, we demonstrated fluid operations with femtoliter to picoliter volumes. Flow-switching within approximately 1 s and a flow control rate in the 63-1341 fL/s range was achieved. In addition, the fluid resistance of the valve was investigated both experimentally and numerically to establish a guideline for designing the valve. The valve developed and the design guidelines obtained will greatly contribute to integrated nanofluidic analytical devices.