Injection molded energy harvesting device

Abstract

Embodiments of an injection molded energy harvesting device are described. In one embodiment, a piezoelectric cantilever is produced via an injection molding method to harvest vibration energy from an environment being sensed. The cantilever device consists of a piezoelectric material member, a proof mass of high density material coupled to the piezoelectric member, and a leadframe for electrical connection. The piezoelectric member is electrically attached to the leadframe with a standard connecting material. The entire assembly is then injection molded with plastic. The plastic encased piezoelectric member forms a cantilever that generates electricity in response to vibration exerted on the proof mass.

1 . A device comprising: 
 a plurality of conductive leads;    a substrate strip coupled to one or more conductive leads of the plurality of conductive leads;    a piezoelectric material coupled to the substrate strip to form a piezo bimorph element;    a proof mass coupled to the bimorph element;    a body coupled to the piezo bimorph element and formed by an injection molding process that encases at least a portion of the piezo bimorph element and at least a portion of the one or more conductive leads.    
   
   
       2 . The device of  claim 1 , wherein the plurality of conductive leads are part of a lead frame comprising one or more rails connected to the plurality of conductive leads, and wherein the body is formed around a portion of the lead frame and electrical leads are formed by removing the one or more rails of the lead frame after forming the body by the injection molding process.  
   
   
       3 . The device of  claim 1 , wherein the piezoelectric material comprises Lead Zirconate Titanate (PZT), and the proof mass comprises tungsten.  
   
   
       4 . The device of  claim 3 , wherein the proof mass is encased in a material formed by the injection molding process.  
   
   
       5 . The device of  claim 1 , wherein the substrate strip comprises one of a plastic substrate, a piezoelectric material substrate, and a strip formed from a portion of the lead frame.  
   
   
       6 . The device of  claim 1  wherein the piezo bimorph element is configured to deflect in a direction corresponding to a vibration force induced onto the proof mass and generate an electric current in response to the vibration force.  
   
   
       7 . The device of  claim 6 , wherein the electric current is provided to a sensor device mounted in a system containing the plastic body to provide operating power to the sensor device.  
   
   
       8 . A system comprising: 
 a microsystem sensor including a sensor circuit, a transmitter circuit coupled to the sensor circuit, and an antenna coupled to the transmitter circuit; and    a power circuit coupled to the microsystem sensor, the microsystem sensor including a plastic body, a piezo bimorph strip coupled to the plastic body, and a proof mass coupled to the plastic body, the plastic body formed by an injection molding process configured to encase the plastic body and leave a portion of the piezo bimorph strip exposed.    
   
   
       9 . The system of  claim 8 , wherein the power circuit is coupled to the microsystem sensor through a plurality of leads, and wherein the plastic body is formed around a lead frame and the electrical leads are formed by removing one or more rails of the lead frame after encasing the plastic body by the injection molding process.  
   
   
       10 . The system of  claim 9 , wherein the piezo bimorph strip comprises a piezoelectric material coupled to a substrate.  
   
   
       11 . The system of  claim 10 , wherein the substrate comprises a strip of material made of one of the following: plastic, piezoelectric material, and metal.  
   
   
       12 . The system of  claim 10  wherein the piezo bimorph strip is configured to deflect in a direction corresponding to a vibration force induced onto the proof mass and generate an electric current in response to the vibration force to provide operating power to the microsystem sensor.  
   
   
       13 . The system of  claim 12 , wherein the piezoelectric material comprises Lead Zirconate Titanate (PZT), and the proof mass comprises tungsten.  
   
   
       14 . The system of  claim 9 , wherein the proof mass is encased within the plastic body formed by the injection molding process.  
   
   
       15 . The system of  claim 9 , microsystem sensor comprises an air pressure sensor.  
   
   
       16 . The system of  claim 15 , wherein the air pressure sensor and power circuit are mounted inside the tire of a vehicle.  
   
   
       17 . A method comprising: 
 providing a lead frame comprising paired conductive members connected to rail elements;    attaching adhesive to one or more conductive members of the lead frame;    attaching a piezoelectric element at least one conductive member of the one or more conductive members of the lead frame;    attaching a proof mass to a first portion of piezoelectric element;    forming an injection molded plastic body around a second portion of the piezoelectric element; and    cutting the rail elements of the lead frame from the plastic body to form separate piezoelectric devices.    
   
   
       18 . The method of  claim 17 , wherein the first portion and second portion of the piezoelectric element are coincident such that the injection molded plastic body is formed around the proof mass.  
   
   
       19 . The method of  claim 17  further comprising the step of forming a piezo bimorph strip by bonding the first portion of the piezoelectric element to a substrate, the substrate comprising a strip material made of one of the following: plastic, piezoelectric material, and metal.  
   
   
       20 . The method of  claim 19 , further comprising the step of leaving portions of the one or more conductive members of the lead frame exposed from the injection molded plastic body to form electrical contacts.