Microfabricated fluid pump

Abstract

A microfabricated fluid pump is formed in a multilayer substrate by etching a plurality of shallow and deep wells into the layers, and then joining these wells with voids formed by anisotropic etching. The voids define a flexible membrane over the substrate which deforms when a force is applied. The force may be provided by an embedded layer of piezoelectric material. Embedded strain gauges may allow self-sensing and convenient, precise operational control.

What is claimed is: 
     
         1 . A microfabricated fluid pump, comprising:
 a multilayer substrate with an embedded layer of a piezoelectric material, the multilayer substrate having a top, center and bottom substrate part, the top substrate part, and having a first flexible membrane formed in the top substrate part which is deflected by the embedded PZT layer;   the center substrate part having a second flexible membrane disposed over a chamber in the bottom substrate part beneath the second flexible membrane,   wherein the first membrane is connected to the second flexible membrane by a first rigid piston in the center substrate part, such that the first and second membranes are coupled together and whereby by the embedded PZT material forms the microfabricated fluid pump by deflecting the first and second membranes.   
     
     
         2 . The microfabricated fluid pump of  claim 1 , wherein the first membrane is perforated by a plurality of holes and the second membrane is unperforated, wherein the chamber is shaped to accommodate the movement of the first rigid piston. 
     
     
         3 . The microfabricated fluid pump of  claim 2 , wherein an inlet valve and an outlet valve allow a fluid to flow into and out of the chamber from an inlet and outlet port. 
     
     
         4 . The microfabricated fluid pump of  claim 3 , wherein the inlet valve and the outlet valve are passive, opening and closing as a result of fluid pressure generated by the deflected membranes. 
     
     
         5 . The microfabricated fluid pump of  claim 4 , wherein the inlet valve and the outlet valve are prestressed, such that they are forced against a stop when no fluid pressure is applied. 
     
     
         6 . The microfabricated fluid pump of  claim 4 , wherein a second and third rigid pistons are disposed laterally adjacent to the first rigid piston, and the second and third rigid pistons are couple to strain gauges to measure a signal indicative of the performance of the microfabricated fluid pump. 
     
     
         7 . The microfabricated fluid pump of  claim 6 , wherein the strain gauges are coupled to a feedback loop that operates the microfabricated fluid pump. 
     
     
         8 . The microfabricated fluid pump of  claim 1 , wherein the substrate parts are comprised of at least one of silicon, glass, polymers, metals, and combinations thereof, and the embedded piezoelectric layer comprises lead zirconate titanate Pb[Zr x Ti 1-x ]O 3 . 
     
     
         9 . The microfabricated fluid pump of  claim 1 , wherein the embedded piezoelectric layer is substantially intact and sandwiched between two conductors, which apply a voltage across the embedded piezoelectric layer. 
     
     
         10 . The microfabricated fluid pump of  claim 1 , wherein the embedded piezoelectric layer is substantially intact and extends across the entire lateral dimension of the device. 
     
     
         11 . The microfabricated fluid pump of  claim 1 , wherein the embedded piezoelectric layer extends across the entire lateral dimension of a total, unseparated fabrication wafer on which a plurality of microfabricated fluid pumps of  claim 1  are formed. 
     
     
         12 . A method for forming a microfabricated fluid pump, comprising:
 providing a multilayer substrate having a top, center and bottom parts;   providing an embedded layer of a piezoelectric material, between the top and center substrate parts;   forming a first flexible membrane in the top layer and the layer of piezoelectric material; and   forming a second flexible membrane in the center part, and a chamber in the bottom part beneath the second flexible membrane, but leaving at least one first rigid piston coupling the first and second flexible membranes to form the fluid pump when a voltage is applied across the piezoelectric layer, such that the first and second membranes are deflected together by the embedded PZT material to form the microfabricated fluid pump.   
     
     
         13 . The method of  claim 12 , further comprising:
 forming a plurality of holes in the first flexible membrane to form a perforated membrane;   forming a chamber in another substrate, wherein the chamber is shaped to accommodate the movement of the piston; and   adhering the substrate with the chamber to the multilayer substrate to form the microfabricated fluid pump.   
     
     
         14 . The method of  claim 13 , further comprising forming an inlet valve and an outlet valve which allow a fluid to flow into and out of the chamber from an inlet and outlet port. 
     
     
         15 . The method of  claim 14 , wherein the inlet valve and the outlet valve and passive, and open and close as a result of fluid pressure generated by the deflected membranes. 
     
     
         16 . The method of  claim 14 , wherein the inlet valve and the outlet valve are prestressed, such that they are pressed against a stop when no fluid pressure is applied. 
     
     
         17 . The method of  claim 12 , further comprising:
 forming a second and third rigid piston structures laterally adjacent to the first rigid piston.   
     
     
         18 . The method of  claim 17 , further comprising forming strain sensors in the second and third rigid piston structures, wherein the strain sensors measure the deflection of the perforated membrane, and thus the fluid pressure in the inlet and outlet port. 
     
     
         19 . The method of  claim 12 , wherein the embedded piezoelectric layer is substantially intact and extends across the entire lateral dimension of the device. 
     
     
         20 . The microfabricated fluid pump of  claim 1 , wherein the embedded piezoelectric layer is substantially intact and extends across the entire lateral dimension of a wafer on which a plurality of microfabricated fluid pumps of  claim 1  are formed.