New Experimental Constraints on Non-Newtonian Forces below $100\mu \mathrm{m}$

We have searched for large deviations from Newtonian gravity by means of a finite-frequency microcantilever-based experiment. Our data eliminate from consideration mechanisms of deviation that posit strengths $\sim {10}^4$ times Newtonian gravity at length scales of $20\mu \mathrm{m}$. This measurement is 3 orders of magnitude more sensitive than others that provide constraints at similar length scales.

Figure 1

Schematic top and side views of test mass on cantilever and drive mass below, showing alternating gold and silicon drive mass bars. Drive mass motion was in the $Y$ direction.

Figure 2

(a) Actuator voltage (left axis), raw cantilever displacement (right axis), and averaged cantilever displacement (right axis, 10 min averaging time) as a function of time over one period of actuator motion. (b) Averaged data for one period of actuator motion for five values of dc current through the drive mass meander.

Figure 3

Background and experimental signal, as well as theoretical thermal noise, as a function of averaging time. The experimental signal levels off at a force of $8.9\times {10}^{-17}\mathrm{N}$.

Figure 4

Strength versus length scale parameter space [see Eq. (1)] for non-Newtonian effects showing area excluded by present (darker shaded region bounded by signal plus $2\sigma$-level error) and previous (lighter shaded region) experiments. Lines labeled Lamoreaux, UWashington, UColorado, and Irvine are from [12], [2], [13], and [14], respectively. Theoretical predictions (dashed lines) are adapted from [15, 4] (dilaton and moduli) and from [1, 16] (gauge bosons).