Small force detection using microcantilevers: Search for sub-millimeter-range deviation from Newtonian gravity.

摘要

Newtonian gravity has been tested on length scales from the astronomical to roughly a millimeter, but this lower limit is still quite large compared to the pertinent quantum mechanical length scale of gravitation, the Planck length. All the other forces of nature have been studied at correspondingly small scales, roughly the Compton wavelength of the interacting particles. Recent theoretical work suggests that exploration of the gravitational force below a millimeter may help explain the hierarchy problem (gravity's weakness compared to the other forces) or put tighter constraints on supersymmetric models. It has been suggested that the discovery of non-Newtonian behavior is possible at length scales in the range of a micron to a millimeter.; In this thesis, the construction of an apparatus for the study of mass-dependent gravity-like forces at length scales below 100 microns is described, and the first data collected with this device are discussed. A silicon microcantilever was utilized as the force sensor in a miniaturized Cavendish-style experiment. Cantilevers of this sort have been recently employed to measure forces in the attoNewton regime, and their small size enables measurement of forces in very small experimental geometries. A metallized silicon nitride membrane was suspended between the attracting masses to minimize electrostatic background forces. This experiment is the first study of gravity-like forces in which the sizes of the masses, force sensor, and mass separation are all less than 1 millimeter; separation between the mass surfaces of 25 microns was attained. These measurements have produced the most stringent constraints on non-Newtonian physics in the range of tens of microns. Theories in which supersymmetry is broken at low energy scales are severely constrained by the almost total elimination of the scalar moduli from consideration.