CAUTION: 3D printed resins change their composition from batch to batch. It is possible that this methodology will not work with some resins, and the PDMS will either not cure or will be covalently stuck on the 3D-printed material. In that case, it will be necessary to surface-modify the parts with Perfluorodecyltrichlorosilane (PFOTS), as in our previous research. We then used the standard replica molding fabrication. Once the 3D printed mold was cured, a solution of 10:1 PDMS/curing agent was mixed, degassed under a vacuum, and poured inside. The PDMS was cured at 70 °C overnight, peeled off the mold, washed with isopropanol and acetone, and air dried. An Inseto Plasma Etch, Inc. PE-25 benchtop air plasma cleaner was used for attaching the PMDS to glass using one cycle of 30 secs at its maximum RF plasma power of 100W with an airflow of ~10 cc/min, which allowed for a vacuum pressure of 200-250 mTorr within the chamber during plasma treatment. The device was left overnight at 70 °C after the plasma attachment. The device was tested with microparticle standards acquired from Whitehouse Scientific ltd. The liquid was manually pushed using a syringe at a flow rate of approximately 2mL per minute in every instance.