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

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

6.3 Power Conversion

Almost all energy available to biological processes on Earth originates in the consumption of the highest naturally-available energy density resource -- nuclear fuels in the Sun. After transfer across space via high-energy photons, this energy is absorbed via photosynthesis by plant life on Earth and converted into chemical energy stores of moderate energy density. These chemical energy stores are then consumed by animal life and converted into mechanical or electric energy stores of lower energy density, or are completely degraded to heat.

Medical nanodevices join this energy ecology by consuming onboard energy stores (Section 6.2) or by absorbing fresh energy resources from the environment, converting these resources into other forms to accomplish useful work and possibly recovering for reuse a portion of this energy via reversible or regenerative processes, then finally releasing heat as the ultimate outcome of irreversible processes. Clearly the key to medical nanorobot power supply is the efficient conversion of energy from one form to another.

The energy conversion matrix in Table 6.2 provides a convenient conceptual framework with which to organize and guide our discussion. Representative technologies are listed for each cell in the matrix. An exhaustive discussion of every matrix element is beyond the scope of this book. Instead, a selection of the most important categories are illustrated with one or two specific examples. Serial chains of multiple conversion processes may in some cases provide increased efficiency over competing pathways, conserve volume or mass, provide faster conversion (e.g., permit higher power density), allow partial energy regeneration, or serve other specific design objectives.

A note on nomenclature: In this book, energy conversion processes are named using the source energy first, followed by the resultant energy form. Thus a device which converts chemical energy into acoustic energy employs a "chemoacoustic" process, and so forth.

Last updated on 18 February 2003