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Analog Angle Blog

Circuitry: Heal Thyself!

There's no doubt that software has gotten smarter, and individual and networked processors have become much more powerful in the past few years. Combined, they can do some amazing things, and the pairing has advanced many aspects of artificial intelligence (AI) quite far, to where these systems can do some impressive things.

Of course, much of the assessment of progress depends on how you define and then measure this “intelligence,” which is as much a philosophical issue as a technical one. After all, things we humans find fairly trivial to do, such as identifying where the road is when driving despite visual clutter, poor and erratic lighting, and generally bad conditions is actually fairly difficult and a very processor/software-intensive image-processing task for an autonomous vehicle.

Yet despite these impressive advances, there's one major area where the physical reality of electronic circuitry still has a long way to go before it can be judged as even close to “life-like.” Many living organisms and creatures are “self-healing” at least to some extent, but there's no comparable capability for circuits. Yet nature is different: a tree with a branch removed (whether due to a storm or a chainsaw) can seal the wound and usually survive nicely, some worms can regrow when cut, and moderate cuts and even broken bones in a person will spur growth of new tissue to try to repair the damaged areas, with results ranging from” so-so” to as good as new.

It's true that there are fault-tolerant systems which can identify and localize a problem, then reconfigure themselves to work around it by re-routing the signal path or switching in backup circuitry; this is often done with power supplies and a paralleled, N+1 topology. However, this type of fault-tolerant design is not the same as one which truly “organically” repairs itself. (True self-healing is a common theme in science-fiction stories and movies; think of the eponymous title character in The Terminator from 1984). While some self-healing materials are available, they require application of external stimuli such as light or heat to activate repair, but a true self-healing function would be self-activated.

The bad news is that any actual implementation of a useful self-diagnosing and healing circuit is not happening anytime soon. The good news is that there is a lot of work being done at universities and NASA-related facilities on various aspects of the problem. NASA certainly makes a lot of sense for this research as spacecraft, especially unmanned ones, obviously would benefit from any viable self-healing technologies.

One of the things I do to keep up with interesting R&D developments which may be somewhat outside the mainstream is to follow the various NASA Tech Briefs updates, usually via their print editions which are easy to scan through. These include lead publication NASA Tech Briefs, plus siblings Medical Design Briefs, Aerospace & Defense Technology, and Medical Design Briefs, and cover both NASA and non-NASA efforts.

Self-healing conductors, interconnects, and insulation would be a nice place to start, as their functions are relatively straightforward, and they are also common sources of system failure. Over the past few years I've seen these reports related to self-healing developments (and you can easily do a broader search through Google, as “self-healing” is a clear and unambiguous keyword):

Making Electronics More Flexible with Self-Healing Gel (see Figure 1)

Figure 1

This self-healing gel combined two gels--a self-assembling metal-ligand gel that provides self-healing properties, and a polymer hydrogel that conducts (from University of Texas at Austin, Cockrell School of Engineering, New 'Self-Healing' Gel Makes Electronics More Flexible).

This self-healing gel combined two gels—a self-assembling metal-ligand gel that provides self-healing properties, and a polymer hydrogel that conducts (from University of Texas at Austin, Cockrell School of Engineering, New ‘Self-Healing’ Gel Makes Electronics More Flexible).

Self-Healing Sensor for ‘Electronic Skin’ (see Figure 2)

Figure 2

A new kind of synthetic polymer is key to development of a self-healing, flexible sensor that mimics the self-healing properties of human skin (from Technion/Israel Institute of Technology, Self-healing-sensor-brings-electronic-skin-closer-to-reality ).

A new kind of synthetic polymer is key to development of a self-healing, flexible sensor that mimics the self-healing properties of human skin (from Technion/Israel Institute of Technology, Self-healing-sensor-brings-electronic-skin-closer-to-reality ).

Self-Healing Spacecraft Material Plugs Holes in Seconds

Self-Healing Electronics Could Reduce Waste

Inkjet-Assisted Creation of Self-Healing Layers Between Composite Plies

Scientists Invent Self-healing Battery Electrode

Self-Healing Wire Insulation (scroll down slightly)

Developing a New Type of Polymer

What's your experience with using some form of redundant circuitry to work around faults? If you could focus on one area for self-healing, what would it be?

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1 comment on “Circuitry: Heal Thyself!

  1. D Feucht
    May 21, 2016

    Interesting topic, Bill. The examples we have of structural reorganization are all biological and they are all “wetware”, not solid-state. We went through the (electron) gas phase with electron tubes, now the solid-state phase with transistors. Perhaps the last and most profound will be liquid-state circuits.

    Liquids have some very strange behaviors involving nonlinear (and chaotic) dynamics, such as the Belousov-Zhabotinsky reaction which shows self-organizing properties caused by nonlinearity. Even something as simple as water flow in an open channel at relatively low speeds can result in hydraulic jumps that are related to shock phenomena in high-speed gases.

    Maybe we should all go back and get our biochemical engineering degrees!

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