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A Robot with a Soft Touch!

Posted on April 20th, 2016 by in New Materials & Applications


Are you up on your knowledge of robots?  An unofficial survey indicates Star Trek – New Generation’s Data, Star War’s R2D2 and Wall.E from the movie with the same name are among the top favorites.  These robots are fun even though or maybe because they function in ways far removed from reality. Famously Lieutenant Commander Data was in all ways human-like except for the ability to feel.  R2D2 is entirely too beepy and too geeky.  The sentimental favorite, for his sensitivity, intelligence and even falling in love with the she-robot Eve, has to be Wall.E.  Give it to Wall.E, he appears to have audio and some rudimentary tactile sense and can detect things that his hands or treads touch.  All those abilities have been, of course, wishful thinking, given the current state of Robotics.  But with smart structures coming of age some of the dreams may be getting closer to reality than we thought. Let’s start with artificial skin, really…

An article in the Proceedings of the National Academy of Sciences defined smart structures as:

“A smart structure is a system containing multifunctional parts that can perform sensing, control, and actuation; it is a primitive analogue of a biological body. Smart materials are used to construct these smart structures, which can perform both sensing and actuation functions.”[1]

Old examples of smart materials include piezoelectric and pyroelectric plastics.  A few examples of materials include inorganic crystals and polymers like polyvinylidene fluoride.  Films of the latter prepared under special conditions respond proportionally to tensile and compressive stress (piezo) and to heat (pyro) by generating a small electric current.  Among the applications of piezoelectric films are stain gauges, vibration sensors, and microphone sensors.  Pyroelectric materials have found use in thermal detectors for temperature measurement and detection of broadband radiation.

There are strong incentives to develop an artificial or electronic skin (e-skin)[2].  Flexible and multifunctional e-skins can find applications in humanoid robotics, skin prosthetics and wearable health monitoring devices.  One critical requirement to using the e-skins for human skin–like tactile sensor applications is the ability to simultaneously perceive and differentiate between multiple spatiotemporal tactile stimuli such as static and dynamic pressure, temperature, and vibration.  E-skins with these capabilities may enable, for example, humanoid robots that can precisely grasp and manipulate objects, discern surface texture and hardness, and feel the warmth of living objects.  Equipping Data with e-skin may be the first step to enabling him to feel too.

In the last decade a number of research groups have demonstrated progress in the development of flexible electronic skins with high tactile sensitivities capable of mimicking the tactile sensing capabilities of the human skin. In October 2015 a paper published by South Korean researchers in Scientific Advances Journal reported significant progress towards building a workable e-skin[2].  The working mechanisms of the human fingertips became the inspiration for those researchers project (Figure 1).

Figure 1 Human skin–inspired multifunctional e-skin. (A) Structural and functional characteristics of human fingertips. (B) Flexible and multimodal ferroelectric e-skin

Fingertip skin consists of slow adapting mechanoreceptors for static touch, fast adapting mechanoreceptors for dynamic touch, free nerve endings (for temperature, fingerprint patterns for texture, and epidermal/dermal interlocked microstructures for tactile signal amplification.  In human fingertips, the fingerprint patterns and interlocked epidermal-dermal micro-ridges play a critical role in amplifying and transferring tactile signals to various mechanoreceptors, enabling spatiotemporal perception of various static and dynamic tactile signals skin[2].

Inspired by the structure and functions of the human fingertip, the researchers fabricated fingerprint-like patterns and interlocked microstructures in ferroelectric films, which can enhance the piezoelectric, pyroelectric, and piezo-resistive sensing of static and dynamic mechano-thermal signals. Our flexible and micro-structured ferroelectric skins can detect and discriminate between multiple spatiotemporal tactile stimuli including static and dynamic pressure, vibration, and temperature with high sensitivities.

As proof-of-concept demonstration, the sensors were used successfully for the simultaneous monitoring of pulse pressure and temperature of artery vessels, precise detection of acoustic sounds, and discrimination of various surface textures skin[2].  The future artificial skins may find applications in robotic skins, wearable sensors, medical diagnostic devices and in number of yet-to-be-determined uses.

Future of Life Institute includes a handful of deep thinkers and public figures such as Elon Musk and Stephen Hawking.  They worry about the day in which humanity is steamrolled by powerful programs run amuck.  Why worry?  It may be a more rational, humane, peaceful and just world!  I can’t recall where I read it: future robots will be just like humans except that humans are flawed.  Just remember Data is now able to feel…

All opinions shared in this post are the author’s own.

[1] W. Cao, H. H. Cudney, and R. Waser, Smart materials and structures, Proc Natl Acad Sci; 96(15): pp8330–8331, July 1999

[2] J. Park, M. Kim, Y. Lee, H. Sang Lee, H. Ko, Fingertip skin–inspired microstructured ferroelectric skins discriminate static/dynamic pressure and temperature stimuli, October 2015



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