Thermal transpiration at the microscale: a Crookes cantilever.
Local temperature inhomogeneities in systems containing micron and submicron objects can result in unexpected consequences. If the mean free path of the host gas constituents is comparable to a characteristic length of the system, then a net exchange of momentum occurs between the constituents and the involved surfaces. For a given temperature gradient and a given pressure range, this results in the presence of Knudsen and Knudsen-like forces (KF). The pressure dependence of these forces has been studied using a microelectromechanical system composed of a microcantilever near a substrate surface. Nano-Newton scale KF are observed by the bending of the microcantilever as monitored by the charge variation on the microcantilever-substrate assembly in a capacitive mode.
Passian
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A
Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. passianan@ornl.gov
Warmack
R J
RJ
Ferrell
T L
TL
Thundat
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T