Accelerating Fluid Loading in Sample Preparation with Fully Programmable Valve Arrays

Microfluidic fully programmable valve array (FPVA) biochips emerge as programmable flow-based labs-on-a-chip consisting of a two-dimensional array of reaction chambers surrounded by four microvalves. Given a mixing tree (represents a sequence of mixing steps) for the target ratio, existing design automation algorithms (DAA) for sample preparation (mixing of reagents in a desired ratio through a sequence of mixing) on FPVA first find the suitable transport-free placement (avoids cumbersome transportation of fluid segment(s) between chambers) and scheduling of mixing operations. After that, reagents are loaded into designated mixer chambers by pushing fluids through input-to-output paths. Since the existing DAA for sample preparation did not consider fluid loading while finding the placement of mixing operations, it often requires a longer and more complex fluid loading path, increasing the sample preparation time and cost. In this paper, we leverage the combinatorial properties of the mixing tree to transform it in favor of finding simpler and shorter paths to load fluids. The simulation results reveal a considerable speedup in the fluid loading time and savings in reagent usage when the proposed algorithm is applied to the mixing tree.