Fabrication and mechanical testing of glass chips for high-pressure synthetic or analytical chemistry

Abstract

The pressure strength of microfluidics glass chips for high-pressure chemistry has been examined. Internal pressures up to 320 bar have been measured, although variations are substantial. Long annealing steps at high temperatures did not show any improvement, but smoothening the powder blasted channel walls by isotropic etching did. Although macro cracks are observed at the bond interface it is believed that the formation of micro cracks in the channel wall and stress concentrations due to sharp corners in the channel crosssection geometry strongly limits the maximum applicable pressures.

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

“…In the first generation high-pressure microreactors the silica fibers had an outer diameter of 360 m, with inner diameters of 40 and 10 m for the inlet and outlet fibers, respectively, and epoxy glue was used (Araldite Rapid TM , Ciba-Geigy, Switzerland) [25]. During preliminary experiments in continuous flow mode it turned out that chip-failure at pressures above 80 bar mostly occurred at one of the inlets.…”

“…2a shows the cross-sectional sideview of the basic inplane inlet/outlet geometry. The maximum pressure (p max ) this geometry can withstand can be improved by avoiding sharp corners where stress-concentrations occur [25]. The latter can be reduced by implementing small cappings in the top wafer (Fig.…”

“…The shape that should withstand the highest pressure is a perfectly circular one, Fig. 2e [26]; however, in practice this situation is extremely difficult to achieve [25]. In Fig.…”

“…Beside that this geometry (Fig. 2e) has the optimal cross-section to obtain high pressures [26], this structure also does not suffer from microcracks that are due to powderblasting [25]. On the other hand, small powderblasted inlets/outlets with a sharp transition towards the flow channels (geometry, Fig.…”

Fracture strength of glass chips for high-pressure microfluidics

“…A few mechanical evaluations have been made on fusion bonded borosilicate glass devices by shortterm pressurization of plugged channel inlet structures to fracture [11][12]. Using H 2 O at rate of 2000 µL/min, 120 µm wide tubular channels resulted in fracture pressures up to 690 bar [11].…”