© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

7.2.4 Nanomechanical Communication

Internal communications (or interdevice communications through hard junctions between linked devices; Section 5.4.2) are readily achieved via sliding or rotating mechanical rods and couplings. A thin diamondoid rod producing 1-nm displacements and oscillating longitudinally at ~1 m/sec may transfer information at ~GHz frequencies. Similarly, a diamondoid transmission line carries acoustic compression pulses at ~17,300 m/sec, providing a >10 GHz bandwidth channel sufficient to support the ~GHz clocking speeds typical of sensors and nanomechanical computers (Section 10.1).

A simple communication mode between unlinked nanorobots operating in close quarters is simple physical tapping. During a 1 microsecond contact event, transfer of 1000 bits is allowed at a 1 GHz line frequency assuming single-threaded transmission; arrays of isolated transmission lines can transmit much more information. Cleavage energies for diamond range from E_cleave = 10.6 J/m² for the {111} crystal plane up to 18.4 J/m² for the {100} plane.⁵³⁶ Adopting the more conservative number to estimate the minimum hammer/anvil cleavage velocity v_cleave, and as a crude approximation, a rodlike diamondoid signal hammer 100 nm in length moving at velocity v_hammer with tip area A_tip = 100 nm² and mass m_hammer ~ 3.5 x 10^-20 kg impacting a diamondoid anvil at speeds of:

{Eqn. 7.14}

cannot cause cleavage in an unfractured anvil structure. The smallest detectable impact for this hammer has energy kT e^SNR = (1/2) m_hammer v_hammer², giving minimum detectable v_hammer ~ 1.3 m/sec for SNR = 2 (Section 4.3.1) at T = 310 K. At this speed, and neglecting anvil mass, a hammer cycled at n_hammer = 1 GHz (~10⁹ bits/sec) against a spring-loaded receiver anvil has a displacement stroke of:

{Eqn. 7.15}

well above the minimum detectable displacement of 10 pm (Section 4.3.1), giving a maximum power cost of kT e^SNR n_hammer ~ 32 pW (~32 zJ/bit).

Mechanical communication can also be achieved by more passive means, as for example the posting of Braille-like tactile-readable information mechanically on the nanorobot surface which may be scanned by neighboring nanorobots using compliant read tips at the distal ends of flexible manipulator arms (Section 5.3.2.5).

Last updated on 19 February 2003