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

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

4.9.1 Acoustic Macrosensing

4.9.1.1 Cyto-Auscultation

Can sounds generated by a single cell be detected, and thus be useful for diagnosis? Probably not, given that low frequency acoustic radiators are notoriously inefficient (Section 7.2.2.1). For example, mitochondrion organelles of the giant amoeba Reticulomyxa are shuttled back and forth by 1-4 cytoplasmic dynein motors while riding on the outside of a bundle of 1-6 microtubules.⁴⁵³ Each dynein motor generates 2.6 pN of force and drives the mitochondria at up to ~10 micron/sec, developing 0.3-1.0 x 10^-16 watts of mechanical power within each 320-nm diameter organelle. Taking each organelle as a cylindrical acoustic radiator with a mechanical input power of P_in ~ 10^-16 watts at n ~ 1000 Hz, the output acoustic pressure at the organelle surface is only ~10^-9 atm (Eqn. 7.6), an acoustic power intensity I ~ 10^-15 watts/m² (Eqn. 4.53) which is not detectable by micron-sized nanorobots. Nevertheless, cells and intracellular elements are capable of vibrating in a dynamic manner with complex harmonics that can be altered by growth factors and by the process of carcinogenesis,¹²⁰¹ so the possibility cannot be completely ruled out.

Last updated on 17 February 2003