R F. DeMara, R. Mercer, and M. Ebel, "Helical Latch for Scalable Boolean Logic 
Operations," Nanotechnology, Vol. 5, No. 3, July, 1994, pp. 137 - 156. 

Abstract: 
Nanomechanical computing elements which employ rotational symmetry and motion 
are designed and analyzed using a bounded continuum model. First, the Boolean 
logic functions of NOT, AND, OR, and XOR are realized using a helical latch, 
reset springs, and rod assemblies. Building upon these components, designs for 
shifters and two-level logic devices are developed. The helical latching 
mechanism calculates the Boolean output function as a positional displacement 
from a known reset state, which occurs exactly once during each 360 degrees 
instruction cycle. Operations of arbitrary word length can be performed by 
subdividing the logic disc into sectors where each sector operates on a single 
bit. Throughput can be increased by pipelining multiple-bit operands to yield a 
speedup which approaches a maximum value of (n+2) as compared to a single-level 
of non-pipelined logic with n inputs. Generally, speedup is bounded by (n+2)/p 
where p denotes the number of cycles between initiations of the pipe. An 
analysis of gate kinematics is performed to determine the device geometries and 
maximum operating frequencies for both non-pipelined and pipelined operation.

Complete Paper Available at:
http://www.cal.ucf.edu/journal/J29_demara_mercer-NANO.pdf