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

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

7.4.6.1 Somesthetic Outmessaging

Human skin contains about 700,000 pressure or touch receptors, mostly concentrated on the fingers (~17,000 receptors on all fingertips) and on the face -- especially the lips and the tip of the tongue. In addition to information about the presence of tactile stimuli, touch receptors can also discriminate both intensity and spatial direction of the stimulus (Table 7.3). Meissner's corpuscle, located in the papillae of the corium just beneath the epidermis, is a receptor for light touch. The Pacinian corpuscle is a deep touch or pressure receptor located in the deep parts of the dermis, in the connective tissue around muscles, tendons, and joints, and in the mesenteries supporting the visceral organs.

A networked population of outmessaging nanorobots, with each nanorobot positioned near a Meissner's or Pacinian corpuscle and capable of triggering artificial nerve impulses (Section 7.4.5.6), could create coordinated spatial and temporal patterns of pressure sensations that could be interpreted by the patient as specific messages. For example, nanorobots neurally emulating the sensation of pressure in the fingers in the sequence Thumb-Thumb-Ring-Index-Thumb are communicating the message "11421" to the user at a transfer rate of 1-10 bits/sec. Similarly, stimulating the arrector muscles artificially triggers the nerve plexus surrounding epidermal hair follicles (which register hair motion), creating well-defined and potentially communicative patterns of "gooseflesh" on the skin.

Mild stimulation of pain receptors (nociceptors), consisting of unmyelinated free sensory nerve endings with pain sensation mediated by the peptide nociceptin, could also produce interpretable messages. For instance, some C fibers when sufficiently stimulated produce burning pain, while small D fibers signal a prickling pain. (There are ~228 pain receptors/cm² in the neck region, ~188/cm² on the back of the hand, ~95/cm² on the radial surface of the middle finger, and ~44/cm² on the tip of the nose).⁸⁶⁹ Heat receptors (brushes of Ruffini) and cold receptors (end bulbs of Krause) also may be employed for outmessaging. Cold spots outnumber warm spots by a factor of 4-10, with temperature receptors concentrated on the face and hands and specific regions showing marked differences in the mix of sensor types (e.g., the forehead contains 0.6 warm receptors/cm² but 8.0 cold receptors/cm²). Nanorobots could employ these neural channels to communicate temporally and spatially-ordered sensations of burning pain, prickly pain, or heat and cold. The maximum serial transfer rate of each of these outmessaging channels to the conscious human mind may be only ~1 bit/sec, although complex spatial and temporal patterns using multiple parallel channels involving significantly higher data flows may be employed in creating full-immersion virtual reality simulations and in related applications (Chapter 25).

The Optacon (Optical-to-Tactile Converter), originally developed by NASA, scanned normal inkprint and converted the characters into a tactile format on a 24 x 6 vibrating-pin array, enabling the blind to feel-read without Braille. Average users achieved ~30 words/min, or up to ~100 words/min in exceptional cases. The Optacon was first sold in 1970 by Telesensory Inc. but is no longer manufactured. Blazie Engineering, Inc., which acquired all rights to the Optacon in 1998, also sells Power Braille, an 81-character 8-dot refreshable Braille display for desktop computer applications.

Last updated on 19 February 2003