Piezoelectric valve module, method for manufacturing the valve module, method for operating the valve module, and respiratory aid device including one or more of the valve modules

A method for manufacturing a valve module, comprising:

• forming a plurality of cavities in a semiconductor body that are separated from each other by a distance;
• forming a plurality of cantilever structures, wherein each cantilever structure is suspended over a respective cavity and being designed to move along one direction only when actuated, that direction corresponding to a positive bending of the cantilever structure away from the cavity, wherein each cantilever structure is spaced apart from a trench adjacent a distal end of that cantilever structure;
• and
• coupling a piezoelectric actuator to each cantilever structure;
• operating each piezoelectric actuator in a plurality of states, including at least:
• a rest state, wherein a given piezoelectric actuator is not biased, in which a first non-zero air flow flows in through the respective cavity associated with that piezoelectric actuator and its cantilever structure and out through the trench;
• and
• an actuated state, wherein the given piezoelectric actuator is biased such that its cantilever structure permits a second non-zero air flow in through the respective cavity associated with that piezoelectric actuator and its cantilever and out through the trench, the second non-zero air flow being greater than the first non-zero air flow.

A valve module adapted to receive at input a first air flow and supply at output a second air flow, comprising:

• a semiconductor body;
• a plurality of cavities in the semiconductor body at a distance from one another;
• a plurality of cantilever structures, each of which is suspended over a respective cavity and is designed to move along one direction only, corresponding to a positive bending of that cantilever structure away from its respective cavity;
• a plurality of piezoelectric actuators, each of which partially covers one respective cantilever structure;
• at least one voltage generator, operatively coupled to said plurality of piezoelectric actuators, to operate each piezoelectric actuator in a plurality of states, including:
• a rest state, wherein that piezoelectric actuator is not biased;
• an occlusion state, wherein that piezoelectric actuator is biased at a first voltage value for which its respective cantilever structure occludes the cavity inhibiting the second air flow;
• a fully-open state, wherein that piezoelectric actuator is biased at a second voltage value, higher than the first voltage value, such as to induce a tensile stress in its respective cantilever structure that causes said positive bending of that cantilever structure with a first entity, thus maximizing the flow rate of the second air flow;
• and
• an intermediate open state, wherein that piezoelectric actuator is biased at a third voltage value, between the first and the second voltage value, so as to induce a tensile stress in that cantilever structure that causes said positive bending of that cantilever structure of a second entity lower than the first entity, thus generating a corresponding intermediate flow rate of the second air flow lower than the maximum flow rate of the second air flow;
• and
• wherein each cantilever structure further comprises a stress-inducing layer, configured to generate, in that cantilever structure, a compressive stress designed as a function of a maximum pressure exerted, in use, by the first air flow on each respective cantilever structure, so that when that piezoelectric actuator is in the rest state, the first air flow does not cause positive bending of that cantilever structure exceeding a preset tolerance value, the positive bending of that cantilever structure allowing a non-zero flow rate of the first air flow.