Microfluidic sputum homogenizer driven by water-head pressure

Homogenizing organism distribution in sputum samples is an initial, yet crucial step to diagnose pulmonary diseases with the samples. Although a homogenization platform for a diagnostic system needs to be system-compatible and efficient, it is rarely implemented. Here, we present a pulsatile micromixer for sputum homogenization that is efficient and does not use dynamic external controllers. The device consists of three oscillator and one mixer units. The oscillator unit autonomously converts a constant input of water-head pressure to a pulsatile pressure, and the mixer unit utilizes this pressure to homogeneously mix two solutions. The mixing performance is analyzed with different oscillation frequencies and width of mixer membranes. The device implemented homogeneous micromixing with a 9 Hz pulse for a flow rate up to 350 μL/min and approximately 200 μL/min for 1 cP and 10 cP viscosity solutions, respectively. Importantly, the device demonstrated successful homogenization of sputum samples with cell viabilities similar to those of the standard method for the flow rate up to 100 μL/min, thereby exhibiting biocompatibility with clinical samples. Our device is potentially useful for various lab-on-a-chip applications that require the compatibility of system integration without sacrificing mixing efficiency.