Thermally Induced Mechanical Loading on Microstructures

Mechanical loading created by thermal inhomogeneity in nonequilibrium systems has fascinated scientists since 19th century. As a unique actuation mechanism, mechanical forces can be created devoid of moving parts and physical contact. The early successful application of thermal force was made by Crookes in 1873, who devised the famous radiometer. Another well-known phenomenon induced by this type of force is thermophoresis, in which a small particle migrates in a gas under the influence of the thermophoretic force stemming from the temperature gradient. With the advent of microfabrication techniques, micro/nano devices with integrated heaters have been routinely made and employed for various applications. The small scale of and the large thermal gradient in these devices provide two necessary conditions for the creation of a new type of thermal force, which may benefit or deteriorate the performance of the devices. In this talk, Knudsen force/torque acting on micro/nano structures will be presented. Its fundamentals, influence on micro devices and potential applications will be discussed.