Finger-powered microfluidic systems using multilayer soft lithography and injection molding processes

TLDR

Point‑of‑care and disposable biomedical applications require low‑power microfluidic systems with integrated pumping components, but external pumps limit portability and power. The authors propose and demonstrate a finger‑powered integrated pumping system that provides a pressure head for advanced microfluidic applications, including on‑chip microdroplet generation. The system employs passive fluidic diodes to route distinct fluids from multiple inlets with a single actuation, and is fabricated using multilayer soft lithography and injection molding. Experimental results show that finger actuation eliminates the need for electrical power, produces a tunable pressure head up to 7.6 kPa, and enables rapid generation of water‑in‑oil and oil‑in‑water droplets and endothelial‑cell encapsulation without external controllers.

Abstract

Point-of-care (POC) and disposable biomedical applications demand low-power microfluidic systems with pumping components that provide controlled pressure sources. Unfortunately, external pumps have hindered the implementation of such microfluidic systems due to limitations associated with portability and power requirements. Here, we propose and demonstrate a 'finger-powered' integrated pumping system as a modular element to provide pressure head for a variety of advanced microfluidic applications, including finger-powered on-chip microdroplet generation. By utilizing a human finger for the actuation force, electrical power sources that are typically needed to generate pressure head were obviated. Passive fluidic diodes were designed and implemented to enable distinct fluids from multiple inlet ports to be pumped using a single actuation source. Both multilayer soft lithography and injection molding processes were investigated for device fabrication and performance. Experimental results revealed that the pressure head generated from a human finger could be tuned based on the geometric characteristics of the pumping system, with a maximum observed pressure of 7.6 ± 0.1 kPa. In addition to the delivery of multiple, distinct fluids into microfluidic channels, we also employed the finger-powered pumping system to achieve the rapid formation of both water-in-oil droplets (106.9 ± 4.3 μm in diameter) and oil-in-water droplets (75.3 ± 12.6 μm in diameter) as well as the encapsulation of endothelial cells in droplets without using any external or electrical controllers.