Biomedical Engineering Reference
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topological form that cells and fascia will tolerate. Squeeze a water balloon in one hand and a
sphere of solid rubber in the other, and the differences become quickly apparent (Hanson and
White, 2004). The use of currently available materials causes the resulting mechanism to be power
hungry, massive, and costing more than $80,000 to manufacture (Menzel and D'Aluisio, 2000); yet,
animatronic-face hardware nevertheless sells vigorously in niche-markets of movie and theme park
animatronics. However, to impact wider markets and to realize the potential of social robots, new
facial materials are necessary.
To overcome this essential hurdle, the author's work advances novel materials that affect human
facial expressions more realistically, with approximately 1/20th the force required by solid elasto-
mers (see Figure 6.13). These materials are low cost, nontoxic (made of medical grade materials),
and altogether practicable for mass production.
The first pass at the material was a urethane-based foamed elastomer which elongated approxi-
mately 500%, yet compressed like a conventional sponge or foam rubber. Dubbed ''F'rubber'' (a
contraction of ''face'' and ''rubber''), the material exhibits physical characteristics much closer to
human skin versus a solid elastomer. The cells of the material are filled with air rather than liquid,
which cause the volume of the simulated tissue to be variable, unlike the practically invariable
volume of liquid-filled facial tissues. Nevertheless, these new materials fold, wrinkle, and bunch in
ways that are highly naturalistic, much more so than can be achieved with solid elastomer. In
addition to improved verisimilitude in simulated facial expressions, this material decreases the
force requirements by an order of magnitude, enabling lower power, lower cost expressive robots,
rendering them applicable to a wider range of art and science.
Figure 6.13 (See color insert following page 302)
UTD human emulation robots with F'rubber.
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