Crack-Photolithography for Membrane-Free Diffusion-Based Micro/Nanofluidic Devices

Recent advances in controlling the cracking phenomena established a novel unconventional fabrication technique to generate mixed-scale patterns/structures with resolution and accuracy comparable to conventional nanofabrication techniques. Here, we adapt our previous cracking-assisted nanofabrication technique (called “crack-photolithography”) relying on only the standard photolithography to develop micro/nanofluidic devices with greatly reduced time and cost. The crack-photolithography makes it possible not only to simultaneously produce micropatterns and nanopatterns with various dimensions but also to replicate both of the mixed-scale patterns in a high-throughput manner. Therefore, a microfluidic channel network can easily be fabricated with a nanochannel array that can function as a nanoporous membrane wherever necessary, which basically plays a key role in diffusion-allowed but convection-suppressed microfluidic devices. In addition, the nanochannel array can manipulate the transport of small molecules by adjusting its dimension and/or number at will, so that nanochannel-array-integrated micro/nanofluidic devices prove even more robust and accurate in diffusion control than conventional membrane-integrated microfluidic devices. As an application of such micro/nanofluidic devices, we employed synthetic bacterial cells and found that their genetic induction and expression are dominated by extracellular diffusive microenvironments that were completely engineered using the nanochannel array. Hence, the crack-photolithography could provide innovative fabrication techniques for unprecedented micro/nanofluidic devices that show substantial potential for a wide range of biological and chemical applications.