The existence of two motive forces on a Crookes radiometer has complicated the investigation of either force independently. The thermal creep shear force, in particular, has been subject to differing interpretations of the direction in which it acts and its order of magnitude. A horizontal vane radiometer design is provided, which isolates the thermal creep shear force. The horizontal vane radiometer is explored through experiment, kinetic theory, and the Direct Simulation Monte Carlo DSMC method. The qualitative agreement between the three methods of investigation is good. The quantitative agreement between the three methods of investigation is better than an order of magnitude in the cases examined. The thermal creep force is found to act from the hot side to the cold side of the vane. The peak in the radiometers angular speed as a function of pressure is found to be explained as much by the behavior of the drag force as by the behavior of the thermal creep force. In addition, this dissertation provides scaling laws between millimeter-scale and micron-scale horizontal vane radiometers, a design of a microelectromechanical system MEMS horizontal vane radiometer, and conceptual designs of two MEMS energy harvesting devices that exploit the thermal creep force.