Dhiman Chatterjee

Micropumps form the heart of several microfluidic systems like micro total analysis system (µTAS) and drug delivery devices, which have resulted from the advancement of silicon micromachining technology. Among the different available types of micropumps, valveless micropumps are better suited for biological applications as they do not have flow-rectifying valves and are less prone to clogging and wear. However, their main drawback is low thermodynamic efficiency. This can be improved if we have a better understanding of the effects of geometry on the performance. This forms one of the objectives of this work. This chapter describes the activity on the design and development of valveless micropumps. A numerical parametric study of the performance of valveless micropumps has been carried out and is presented to bring out the effects of different geometrical parameters. Based on these design approaches, silicon-based micropumps are fabricated and characterized. The performance of one of these micropumps is compared with designed value in this work.

With constraints on size, cost, reliability, and performance for liquid-based cooling systems, the design of modular micropumps suitable for an integrated thermal management system still remains a challenge. In this paper, the effectiveness of a low-cost valveless micropump-heat exchanger on a printed circuit board is investigated for electronic cooling. Signal conditioning and control electronics are integrated with the fluidic components on the substrate to form a compact modular unit. Piezoelectric actuation and conical diffusers are utilized to generate pulsating flow through a minichannel heat sink. With ethanol as the working fluid, the tested pump reached a maximum flowrate and a pressure head of 2.4 ml/min and 743 Pa at an input voltage of 6 VDC. Suitability of the system for active real-time temperature control has been demonstrated at two input heater power levels of 1.45 and 2.5W A maximum reduction of 57 per cent in the average heat sink surface temperature could be achieved at a maximum power consumption of 150 mW by the micropump. © IMechE 2009.

In this paper, performance of piezoelectrically actuated pyramidal valveless micropumps is studied experimentally in detail. Valveless micropumps based on silicon and glass substrate are fabricated using MEMS technology. Two different sizes of micropumps having overall dimensions of 5 mm × 5 mm × 1 mm and 10 mm × 10 mm × 1 mm are fabricated and characterized. In the fabricated micropumps, the thickness of silicon diaphragm is <20 µm which gives the advantage of operating pump at low voltage with excellent stability and consistency. The performance of micropumps in terms of flowrate and backpressure is evaluated for a wide range of driving frequency and actuating voltages. The maximum flowrate of water in the 10-mm micropump is 355 µl/min and backpressure of 3.1 kPa at zero flowrate for an applied voltage of 80 V at frequency 1.05 kHz. The reported micropumps have low footprint, high flowrate and backpressure. Thus, these micropumps are especially suited for biological applications as these can withstand adequate amount of backpressure. Comparative study of the performance of these micropumps with those available in the literature brings out the efficacy of these micropumps.