Microfluidic very large scale integration (mVLSI) with integrated micromechanical valves

TLDR

Microfluidic chips with high‑density control elements are needed to improve throughput, sensitivity, and dynamic range. The authors aim to create robust, accessible high‑density microfluidic chips by fabricating a monolithic three‑layer PDMS valve architecture that replaces the standard two‑layer design. The architecture is built via multi‑layer soft lithography, enabling low‑cost, easy fabrication. The valves, sized 8 × 8 and 6 × 6 µm², operate at 180 kPa and 280 kPa respectively, achieving densities near 1 million valves cm⁻²—over two orders of magnitude higher than current mLSI—while remaining leak‑proof and addressable through multiplexing, as shown by fluorescent bead tracking and resistance‑change experiments.

Abstract

Microfluidic chips with a high density of control elements are required to improve device performance parameters, such as throughput, sensitivity and dynamic range. In order to realize robust and accessible high-density microfluidic chips, we have fabricated a monolithic PDMS valve architecture with three layers, replacing the commonly used two-layer design. The design is realized through multi-layer soft lithography techniques, making it low cost and easy to fabricate. By carefully determining the process conditions of PDMS, we have demonstrated that 8 × 8 and 6 × 6 μm2 valve sizes can be operated at around 180 and 280 kPa differential pressure, respectively. We have shown that these valves can be fabricated at densities approaching 1 million valves per cm2, substantially exceeding the current state of the art of microfluidic large-scale integration (mLSI) (thousands of valves per cm2). Because the density increase is greater than two orders of magnitude, we describe this technology as microfluidic very large scale integration (mVLSI), analogous to its electronic counterpart. We have captured and tracked fluorescent beads, and changed the electrical resistance of a fluidic channel by using these miniaturized valves in two different experiments, demonstrating that the valves are leakproof. We have also demonstrated that these valves can be addressed through multiplexing.