Engineers at Purdue University in the US have developed a micromachined pump to circulate cooling water through channels etched into a chip.
“Because it’s a MEMS pump, we were able to integrate the entire cooling system right onto a chip,” said project leader Professor Suresh Garimella.
The channels are about 100µm wide and within these are hundreds of electrodes connected so that every sixth electrode gets the same waveform.
Phasing is such that a travelling electric field is created which drags the water along by electrohydrodynamics - the interaction of ions and electric fields causing fluid to flow.
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Researcher Brian Iverson with the micro pump devices
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A thin sheet of piezoelectric material is used as a top cover.
By energising this, a further 13 per cent flow is produced. Modelling suggests this could be increased to over 100 per cent, said Purdue.
One thousand times more energy is shifted than is consumed.
“We have shown that the power input required is in the microwatts, but you can get milliwatts of cooling,” said Garimella.
“One big challenge is further developing mathematical models that are comprehensive and accurate because this is a very complicated, dynamic system. You’ve got fluid flow on a micro-scale, you’ve got electrohydrodynamic effects, electrical fields and a moving diaphragm,” he said.
In April last year, Purdue researchers under Professor Issam Mudawar announced a copper evaporative heat exchanger for chips incorporating a network of 231x713µm channels and using commercial refrigerant R134a, but an external pump.
Purdue University