A great challenge for the burgeoning field of nanotechnology is the design and construction of microscopic motors that can use input energy to drive directed motion in the face of inescapable thermal and other noise. Driving such motion is what protein motors—perfected over the course of millions of years by evolution—do in every cell in our bodies. 1
To put the magnitude of the thermal noise in perspective, consider that the chemical power available to a typical molecular motor, which consumes around 100–1000 molecules of adenosine triphosphate (ATP) per second, is 10−16 to 10−17 W. In comparison, a molecular motor moving through water exchanges about 4 × 10−21 J (the thermal energy kT at room temperature) with its environment in a thermal relaxation time of order 10−13 s. Thus, a thermal noise power of about 10−8 W continually washes back and forth over the molecule....
