  A micromechanical torsion oscillator has been used to strengthen the limits
on new Yukawa forces by determining the Casimir pressure between two
gold-coated plates. By significantly reducing the random errors and obtaining
the electronic parameters of the gold coatings, we were able to conclusively
exclude the predictions of large thermal effects below 1 $\mu$m and strengthen
the constraints on Yukawa corrections to Newtonian gravity in the interaction
range from 29.5 nm to 86 nm.
