Manufacturing of physical devices by stacking atoms together is the ultimate goal in nanotechnology. A mechanical manipulation device for such purpose would require positioning accuracy just a fraction of the distance between two adjacent atoms. It also has to be dexterous enough to maneuver the payload atoms around without interfering or causing damage to the work piece. Various mechanical devices have been proposed in the past for nano-scale manipulation ranging from robotic arms to parallel manipulators, including the Stewart platforms. This paper reviews (with an emphasis on Stewart platforms) the theory of parallel manipulators and discusses the feasibility of utilizing parallel mechanisms for molecular manufacturing and assembly.
Various functional requirements and architectural constraints are included in the feasibility study. Selective mechanical control of reactions in diamond requires position accuracy in the neighborhood of an angstrom. This implies that the manipulator must be stiff enough to resist thermal disturbances. It also requires high positional resolution actuators. Workspace requirements and dimensional constraints are also considered. Additional criteria desirable for the robotic approach are introduced including orientation capability and accuracy. Strategies that would loosen certain requirements at the component architectural level are also investigated.
Singularities of the parallel manipulator and its influence on molecular manufacturing are discussed. Since the stiffness of a parallel manipulator decreases near the singular positions, it is important that singularity avoidance be considered at both the design and the operational stage. Subsequently, issues pertinent to the optimal design and the operation of nano-manipulators are studied.
C. K. Kevin Jui
Department of Mechanical and Manufacturing Engineering, University of Calgary
2500 University Dr. N.W., Calgary, Alberta, Canada, T2N 1N2
Phone: (403)220-3632; Fax: (403)282-8406