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

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

5.2.3 Intracellular Nanodevices

Nanodevices intended to perform tasks inside human tissues by leaving the bloodstream and entering the cell or nucleus will require a physical configuration consistent with the particular mission and the specialized tools required (Chapter 21). Metamorphic surfaces may assist in cyto devices in achieving nondisruptive membrane penetrations (Section 9.4.5), deployment and manipulation of flexible mechanical pseudopods or motive appendages (Sections 5.3.1 and 9.3.1.6), and reconfiguration of sensors or other subsystems (Section 5.3.5). Cell repair nanorobots could adopt one configuration to seek the target cell, a second to penetrate the membrane, and yet a third while operating within the cytosol.

Basic device shape will not be driven by hydrodynamic considerations because cell repair nanorobots spend the bulk of their operational time on site, not in transit, and need move only relatively slowly when they travel between worksites (Chapter 21). Nor will device shape be governed by tessellation rules (Section 5.2.4), since these machines will normally spend most of their time in solitary activity or at least out of direct physical contact with other nanorobots working nearby (Chapter 21). Thus the strongest purely geometric influence on these most complex of nanodevices may be volume storage efficiency. A spherical shape or near-spherical icosahedral shape (as in many viruses) can contain the largest possible mass of nanocomputers, mass memory, power supplies, repair consumables, specialized tools, communications and navigational equipment, and so forth.

However, cellular repair machines may also need to dock with other nanomachines at irregular intervals to receive supplemental materials, fuel, or information, so it would be convenient to use a shape with a large number of planar faces across which such transfers might readily be effected. A space-filling shape (Section 5.2.5) also allows ready aggregation of operational units in vivo for ad hoc conferencing plus efficient storage of unused units. A truncated octahedron with a total of 14 hexagonal and square faces (Section 5.2.5) is the space-filling polygonal shape with the highest volume/surface ratio, closest to the sphere (Table 5.1).

Last updated on 17 February 2003