POWER MEMS ( micro electro mechanical system)
The term “Power MEMS” was first suggested by Epstein and Senturia in 1996 to describe microsystems which generated power or pumped heat. Their particular interest was MEMS heat engines, specifically Brayton cycles (such as gas turbines) and Rankine cycles (such as steam engines) and subsystems thereof. The promise identified was microsystems whose power densities equaled or exceeded those of the more familiar large-scale devices. Since that time, the Power MEMS system has evolved into a broader concept which includes other traditional thermal cycles, new heat engine concepts which may only be attractive at microscale, energy harvesting schemes, and even micro-fuel cells. Heat engines convert chemical energy into heat and then mechanical work. This mechanical energy may be used directly for applications such as vehicle propulsion or fluid pumping or converted into electric power. For example, propulsion is the goal of MEMS gas turbine and rocket engines, while MEMS gas turbine and internal combustion engines are being developed to power electric generators of various designs for electric power production. Power MEMS also encompasses heat engines which convert chemical energy directly to electrical energy, usually using the thermoelectric effect. These devices may be intended primarily as power generators or may have a different primary function such as fuel reforming for fuel cells with the power generation (or scavenging) being a secondary consideration. Power MEMS also includes devices which convert mechanical energy into electric power. This includes such devices as a self-charging electric watch and heel strike power generators.
The literature of MEMS power systems tends to fall into two categories: (1) descriptions of the overall system concept and its realizations, and (2) progress in the enabling technologies needed to realize such system concepts. The objectives of this review paper are twofold. The first is to informally survey ongoing Power MEMS projects. The second is to note technology challenges common to many of the approaches which may form fruitful research areas.