A microfluidic diaphragm valve. The valve comprises: an inlet port; an outlet port; a weir positioned between the inlet and outlet ports, the weir having a sealing surface; a diaphragm membrane for sealing engagement with the sealing surface; and a thermal bend actuator for moving the diaphragm membrane between a closed position in which the membrane is sealingly engaged with the sealing surface and an open position in which the membrane is disengaged from said sealing surface.