A thermopneumatic dispensing micropump

A micropump for dispensing microliter liquid volumes is realized by warming a thermopneumatic fluid that expands a membrane to pressurize a liquid reservoir with an outlet flow restrictor. The temperature of this liquid-vapor perfluorocarbon mixture is controlled by a thin film heater. The outlet flow restrictors, used in this work, are 75-100 mum silica capillaries, which result in microliter per minute flow rates at 7-42 kPa liquid pressure levels. We investigate both open loop designs and closed loop designs with pressure feedback. The closed loop designs offer increased transient and steady state flow control and allow a much larger range of pump geometries compared to open loop designs. The micropump dispenses 1.4 mul/min for 4.5 h with an average power of 200 mW. Due to its design with no moving parts, this thermopneumatic pump is low cost and simple in construction. The basic principles appear suited to MEMS fabrication, and so would have potential applications for micro total chemical analysis systems (muTAS), biosensors, and "lab-on-a-chip" devices. (C) 2004 Elsevier B.V. All rights reserved.