Nanomedicine, Volume I: Basic Capabilities

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

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

Uninsulated wires risk electrical leakage and unnecessary heat transfer; unshielded wires produce stray fields that may attract unwanted attention from mobile elements of the immune system, e.g., electrosensitive leukotaxis (Section Thus coaxial cable or "coax" is the proper transmission line for in vivo electrical cable communications. Unlike waveguides, coaxial cable is not a resonant device, hence the traveling wave frequencies it carries may be varied continuously down to DC. The electric fields within a coax line have axial symmetry. However, serious design complications may arise if the transmitted wavelength (l) is less than the circumference of the annular dielectric space between the conductors, because a second (nonaxial) mode of rf propagation with diametral symmetry can then be excited simultaneously. To avoid this complication, a 1-micron diameter coax should be held to a practical upper frequency limit of c / p dcoax < 1 x 1014 Hz for cable lengths >> l.

Intracoaxial scattering and absorption are negligible, so for single-channel bandwidth the maximum coaxial bit rate 'Imax consistent with a nanorobot onboard communication power budget Pcomm using rf or microwave photons (hncoax / kT ln(2) << 1) occurs at the full-power transmission frequency

{Eqn. 7.16}

Thus the maximum coaxial transmission frequency is 0.1 GHz (108 bits/sec) for Pcomm = 0.3 pW, 1 GHz at 3 pW, and 100 GHz (1011 bits/sec) for Pcomm = 300 pW (>3 zJ/bit).


Last updated on 19 February 2003