© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.

Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.

B.4.3.3 Piston Operation in the Desorption and Viscous Regimes

A rectangular hydrogen-terminated diamond piston plate moves back and forth inside a cavity whose walls also consist of hydrogen-terminated diamond. The outward-facing surface of the piston plate and the inward-facing surfaces of the piston cavity are exposed directly to the external solvent environment. A molecular dynamics simulation of hexadecane wetting the Au(001) surface at 315 K shows that the initial monolayer is complete in ~1 x 10^-9 sec [3217]; another simulation study of liquid octane near a waxy interface required ~0.4 x 10^-9 sec for monolayer adsorption equilibration [3232], and equilibration times of 0.3-1 x 10^-9 sec are typical in alkane film adsorption or confined liquid studies [3185]. For our assembler design, we assume that predominantly n-octane molecules physisorb to the passivated diamond walls in a time t_adsorb ~ 1 x 10^-9 sec << t_piston = (2 n_piston)^-1 = 50 x 10^-9 sec. Hence, throughout each return stroke of the piston (wherein the cavity is reduced to zero volume), all cavity walls that are still exposed to solvent should be reliably coated with a complete physisorbed monolayer of n-octane molecules.

Last updated on 13 August 2005