Fabrication of whole-thermoplastic normally closed microvalve, micro check valve, and micropump

There is a critical need to develop fabrication methods for rapid and cost-effective prototyping of thermoplastics-based microfluidics in academic research laboratories. This paper presents a method for the fabrication of whole-thermoplastic microfluidic functional elements, including a pneumatic (gas actuated) normally closed microvalve, a micro-check valve, and a pneumatic dual-phase micropump. All devices were made from thermoplastic polyurethane (TPU) and poly(methyl methacrylate) (PMMA). The fabrication process consisted of only laser micromachining and thermal fusion bonding without need to perform any particular chemical treatment or use a master mold. These features enable the widespread adaptation of this method in academic research settings. Characterizations revealed that the fabricated normally closed microvalve could stop liquid flows at pressures lower than 2 psi in its passive operation mode where no pressure was used for valve actuation. The check valve could block liquid flows with liquid pressures of up to 30 psi in its reverse mode of operation while it could allow liquid to pass through in its forward mode. In addition, the micropump, which consisted of two check valves and a pneumatic uni-diaphragm displacement chamber, could pump liquid at an average flow rate of 87.6 +/- 5.0 mu L/min using an actuation frequency and pressure of 1 Hz and +5 psi, respectively. Taken together, the developed low-cost whole-thermoplastic microfluidic functional elements could be employed for the fabrication of various lab-on-a-chip applications. (C) 2017 Published by Elsevier B.V.