Failure mechanisms of pressurized microchannels, model, and experiments

Microchannels were created by fusion bonding of a Pyrex cover to a thermall y oxidized silicon wafer, which contained anisotropically etched grooves. S uch channels are frequently used in microfluidic handling systems, for exam ple, in chemical analysis. Since in some of these labs-on-a-chip, in partic ular those used in liquid chromatography, the channels are subjected to hig h pressures of up to a few hundred bar, it is important to have information about the mechanical stability of the channel chip, in particular of the w afer bond involved in it. The latter is the subject of this paper, The maxi mum pressure that can be applied to several different channel chips was inv estigated experimentally. In order to find the relation among this maximum pressure, channel geometry; materials elasticity, and bond energy, an energ y model was developed that is generally applicable to all types of wafer bo nds. It was shown that the model is substantiated by the experimental press ure data, from which it could be calculated that the effective bond energy increased from 0.018 to 0.19 J/m(2) for an annealing temperature ranging fr om 310 to 470 degreesC.