Bypass resistive pulse sensor by MEMS technology

Resistive Pulse Sensing has recently emerged as a promising technique for measuring and counting particles in electrolyte solutions, with applications in nanoparticle characterization, biomolecule analysis in micro-fluidic sensing. Resistive Pulse Sensing offers high single-particle sensitivity, real-time, and label-free detection. It can provide detailed information on particles including size and shape. Small pore diameters are required to detect small particles, but they limit the measurable range and carry the risk of clogging. This paper presents recent advancements in wafer-level Micro-Electro-Mechanical Systems technology specifically tailored for fabrication of microflow cells for Resistive Pulse Sensing. Key processes include femtosecond laser structuring, photolithography, etching, deposition, and bonding technologies which allow to enhance the scalability and reproducibility of the sensing platforms because they enable precise control of dimensional parameters that determine the sensitivity. To avoid clogging of very sensitive systems with very narrow pores, a bypass flow architecture was implemented that allows particles that are too large to pass through the pores to leave the sensor system. The bypass system also offers the advantage of operating without the need for sample filtration. The fabricated sensors are reusable, durable, and practical for diverse applications. Two types of micropores were fabricated, each 100 μm in length and square cross-sections with nominal edge lengths of 8 μm and 1 μm. The RPS measurement using both pores demonstrated the ability of the system to determine particle sizes with an uncertainty of +/- 10%. The Resistive Pulse Sensing measurement with the 1 μm pore proved to detect nanoparticles as small as 350 nm in diameter.