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

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

5.4.1 Nanojunction Mechanisms

Neighboring nanorobots must be able to reliably identify the presence of others and then join together tightly into cohesive nanotissues, forming planar or three-dimensional arrays. In nanodevices, a broad array of fastening technologies from both the biological⁵³³ and the engineering¹⁶¹⁴ worlds is available for design inspiration.

For simple adhesion, micromechanical velcro,⁵³² sticky tethers,⁵³⁵ magnetic latches (F_min ~ 1600 nN for A_magnet = 1 micron², B = B_magnet = 1.4 tesla; Eqn. 4.45), or other mechanical adhesives offer the simplest means of attachment. Interlocking mechanisms are common in engineered materials (e.g., plug and socket, hook and eye, distension bulbs or dilators) -- many of which are simple derivations of two simple machines (the plane and lever) commonly employed in mechanical engineering. Hepatic cells comprising liver walls are connected by "pegs" that fit into depressions in neighboring cells in a crude analogy to snap fasteners (Section 8.2.5, and see below); similar knobbed adhesive interfaces¹⁰ and docking envelopes¹⁶¹⁴ have been proposed for nanodevices. Complementary knobs of various shapes may also be used on the surfaces of different nanorobot species, or on different faces of the same species, to provide simple mechanical recognition or orientational control. Judicious selection of device shape which mandates specific mateable junction geometries can force a large nanorobot aggregate into desired global configurations (e.g., structured nano-organs).

Pressed tightly together, two complementary diamondoid surfaces create a strong van der Waals adhesive interface with tensile strength ~3 x 10⁹ N/m²; interposing scattered atomic-scale bumps ~0.2 nm in diameter reduces this adhesion to ~3 x 10⁸ N/m² ,¹⁰ or ~3000 atm (Section 9.2.1). Providing each metamorphic nanorobot species with complementary Braille-like adhesion plates may provide either a simple means of universal attachment or a unique recognition and interlock pattern of great complexity. Adherent plates are readily detached by inserting corrugated wedge mechanisms or by deforming the adhesive pattern. For comparison, adhesion between biological cells (as determined by measurements of the force required for detachment of ~20-micron tissue cells by micromanipulation, shear, or jets of fluid) is typically ~1-100 nN/micron².^{1454,1455,1458,1459}

Reversible adhesion may also be achieved using surface-mounted matched nanomechanical manipulator arms (Section 9.3.1) which can grasp or release their counterpart in an adjacent cell, under computer control.

Last updated on 18 February 2003