Abstract: Flat-bottomed cavities are formed in a substrate (2) by a method comprising two etching steps: a first anisotropic etching through a mask (4) leaving exposed bands (6,8) of the substrate (2) and a second anisotropic etching through a mask leaving exposed all of the zones (Z1, Z2) to be etched. The first etching provides grooves in V form (10,12), the depth of X.sub.1, X.sub.2) which depends on the width of the bands, while the second etching increased the depth of the cavities by the same amount y, in eliminating the bands located between the grooves. Advantage: flat cavities of different depths may be obtained simultaneously.

Abstract: A valve is formed by machining a silicon wafer 18 bonded to a glass wafer 2. This machining forms a membrane 44 and a sealing ring. Part of the surface of the membrane 44 and optionally the sealing ring are oxidized in order to impart a mechanical pre-tension to the membrane holding the valve in a closed position. Further etching 52 may be carried out in a manner such that in the absence of the aforesaid pre-tension the valve is in the open position at rest.

Abstract: A valve is formed from a silicon wafer (20) and has a position detector to detect by contact the position of the valve and hence reveal any malfunction. The position detector comprises a first electrical contact (54) formed on a glass support (32) mounted on the back face of the wafer (20), a second electrical contact fixed to the wafer (20) and an electrical impedance measurement circuit (resistance or capacitance according to the embodiment) between the two electrical contacts. The valve is useful in a micropump for the injection of medicaments.

Abstract: Pumping takes place within the micro-pump as a result of the deformation of a plate (12) using a piezo-electric pad (13). The deformation produces a variation in volume within a pumping chamber (15) defined inside a plate (11) which is made of a material which can be machined using photolithographic processes. The pump outlet (3) is blocked off, selectively, by a membraned check-valve (18) which is in direct communication with another check-valve (16) via the pumping chamber. The check-valve (16) selectively enables the pumping chamber to communicate with the pump inlet (2). The outlet valve membrane (18) has a layer of oxide (17) providing a pretension on closing. The check-valve thus has a regulatory effect on the pump operation, making the flow almost independent of the outlet (3) pressure. Application: injection of exact doses of medication.

Abstract: The micropump comprises a silicon wafer (22), glass wafers (2, 24) and a control element (26). The wafer (22) is machined to define an inlet valve (36), a pump chamber (34) and an outlet valve (48). The inlet valve (36) comprises a membrane (40) defining an upstream compartment (38) and a downstream compartment (62), an orifice (42) and a sealing ring (46) surrounding this orifice. The orifice (42) is pierced at a location in such a way that, during the priming of the micropump, the fluid arriving in the downstream compartment reaches a specific and unique part (60) of the downstream compartment wall before reaching other parts of the wall. The fluid is then propelled along the wall on both sides of the part (60) by pushing the air away ahead of it and thus guaranteeing that no air bubble can be formed in the downstream compartment.