A thermopneumatic valveless micropump with a PDMS-based nozzle/diffuser structure was firstly designed and realized herein by stacking three layers of PDMS on a glass slide. Unlike the conventional peristaltic pumping configuration, the new structure of the micropump shown in Fig. 1 consists of only one set of heater on the glass slide, a thermopneumatic actuation chamber, and an actuation diaphragm. Additionally it includes a microchannel with nozzle/diffuser structure and inlet/outlet ports. In this valveless microchannel, fluid is driven by asymmetric flow resistance produced from the nozzle/diffuser configuration. The actuation diaphragm between the gas-pneumatic chamber and the flowing channel can bend up and down by exploiting air expansion that is induced by increasing heater temperature. PDMS has good characteristics: it is cheap, transparent, easy to fabricate and biocompatible. But in the micropump, the porosity of PDMS causes several critical problems such as bubble formation and sample evaporation. To solve those problems, we coated the micropump with parylene film, which has low permeability to moisture.
Proceedings of the 4th Asia Pacific Conference on Transducers and Micro-Nano Technologies (APCOT 2008)，4p.