The Future is Soft?

As Synthetic Biology develops it will converge with, and mutually accelerate, many other disciplines. It is already beginning to do this with its closest relatives and, in this author’s opinion, one potentially very fruitful confluence of disciplines could still be found in the merging of Synthetic Biology and Soft Robotics. They both celebrate unconventionality and are at their core the engineering of unique biomimetic devices. As a result, they are highly complementary.

 

So, what is Soft Robotics? It is not a well-known discipline, although that may soon change with Hollywood exposure (see Big Hero 6), and I find it’s best described by initially thinking about traditional robotics. What do you picture when you hear the word robot? Predominantly humanoid looking machines made out of traditional materials like metal and plastic? They probably also have traditional electrical power and control systems (electrochemical batteries and printed circuit boards). I imagine you are probably thinking something along the lines of a Dalek or the Terminator (the T 800 not the T 1000).

 

All of these components and systems are very rigid, inelastic and completely antithetical to natural biological tissues. This can mean trying to use inspiration from nature to improve robots built from traditional, rigid hardware can be very difficult. This is because you are trying to translate phenomena that has emerged from a soft/hybrid morphology. Soft Robotics is attempting to broaden the horizon of robotics to include novel (soft) materials and control systems. This allows the discipline to be more biomimetic and use natural systems for inspiration (potentially unlocking unique functionalities). Why can’t robots look like a crawling caterpillar or an undulating octopus (i.e. have a motility dependent on cyclical squelching)? Could they run on chemical reactions within a microfluidics circuit? Could they be biodegradable? Or made out of hydrogels, flexible plastics or cell-like vesicle aggregates etc.

 

If you look in biology, and you ask what Darwinian evolution has coughed up, there are all kinds of incredible solutions to movement, sensing, gripping, feeding, hunting, swimming, walking and gliding that have not been open to hard robots

George Whitesides

 

For example: our legs actuate using antagonistic pairs of muscles (like the biceps and the triceps cooperating in our arms). A lot of the efficiency in their movement comes from the structure of the muscles themselves. Due to their elasticity they store mechanical energy when compressed and stretched. This means during running they are passively recycling a lot of the energy put into them. That kind of locomotion cannot be reiterated in hard materials. This ability of a material, via its composition or morphology, to unconsciously respond to external stimuli to improve its own performance is called ‘embedded intelligence’. It is very common in natural biological tissues and it is a key tenet of soft robotics.

 

Materials that are highly compliant (i.e. soft) can mitigate unpredictability and can translate simple types of actuation into complex motion. They are also more biocompatible. Wouldn’t an exoskeleton be more comfortable and compatible if it could flex and twist like our body can? And there is no need to stop at wearable technologies. Soft robotics could also be used in regenerative medicine, replacing or enhancing tissues/limbs, or tiny soft robots could be in a pill you swallow which then go on to do something inside your body e.g. perform a diagnosis or a surgery. Soft robotics is also particularly amenable for the miniaturization of mechatronics (utilizing smart materials and nanotechnology etc.), interacting with sensitive objects (such as picking fruit) and unconventional sensing devices (like deformable tactile sensors).

 

However, one of the biggest challenges in soft robotics right now is a lack of holistic design i.e. a completely soft device made completely out of deformable materials. Most contemporary soft robots currently remain attached or tethered to hard energy sources such as batteries or compressed air tanks. But soft robotics, like synthetic biology, is still in its infancy. Is it possible that SynBio could build some of the materials that soft robotics needs to develop? Could soft robots run on a microbial fuel cell (housed within a soft body) battery? And could Synthetic Biology design microbes efficient enough to run the battery? Why can’t control be more similar to the neuronal or endocrine systems we have? Could a soft robot run on photosynthesis or a close analogue? Why not?

 

 

 

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