A new kind of pump – as thin and small as a credit card – could pave the way for wearable assistive devices for people with disabilities and people suffering from age-related muscle degeneration.
The study is published in the Feb 17. edition of Science Robotics .
A stretchable, twistable muscle-like material has frequently been used to power soft robots and assistive clothing. The pneumatic artificial muscles, however, have been traditionally powered by conventional, motor-driven electromagnetic pumps, which are bulky, noisy, complex, and expensive.
Researchers from Bristol's SoftLab and Bristol Robotics Laboratory, led by robotics Professor Jonathan Rossiter , have successfully demonstrated a new electro-pneumatic pump that is soft, bendable, low-cost, and relatively simple to make, according to the team.
In a short Q&A with Tech Briefs below, Rossiter describes how the new, card-sized soft pump can power pneumatic-bubble artificial muscles and a variety of other intriguing applications, like stylish, power-assisting clothing.
Tech Briefs: What is robotic clothing, and what role will your pump play in supporting it?
Prof. Jonathan Rossiter: For people who have problems moving around, for example, if they are suffering from age-related muscle weakness or stroke, robotic power assistance can help them maintain their independence.
Current robotics exoskeletons can help but are made of motors and hard metals and plastics, and these make them uncomfortable, difficult to put on, difficult to adapt to different people, expensive, and ugly.
Robotic clothing is a bit like an exoskeleton that you wear as clothing. It will be comfortable, unobtrusive, low-cost, and easy to put on and take off. Instead of motors, we use soft artificial muscles to provide the mechanical power assistance and help people move.
Tech Briefs: What’s the operating principle of this new pump, and how does it differ from conventional electromagnetic pumps?
Prof. Rossiter: Our power clothing uses artificial muscles driven by air. This makes them very low-cost and flexible. Until now, we have had to use motor-driven pumps to generate the compressed air for the muscles. Unfortunately, these pumps are bulky, noisy, and hard, and are not easy, or comfortable, to put in clothing. This has held back the development of truly soft robotic garments.
Our new Electro-Pneumatic pump can also drive our artificial muscles but, in contrast to motor-driven pumps, is flexible and thin (thinner than a credit card), and can be incorporated easily in clothing. The Electro-Pneumatic pump uses two physical electrostatic phenomena, working in tandem, to effectively squash air between two flexible conducting electrodes. This squashing generates the pneumatic power needed to drive artificial muscles. Because the Electro-Pneumatic pump runs off electricity, the only hard component in the power clothing will be the battery, and this could be as small as the battery inside a mobile phone.
Tech Briefs: Why have soft pumps been such a challenge to make, and how did your design overcome those challenges?
Prof. Rossiter: Hard electric motors are very well understood and very efficient. To replace them in a soft design is not easy!
The physics is different and has taken much work to understand and perfect. Instead of using magnetics — the science behind motors — we have used electrostatics which exploit the interplay of electrical charges. One of our challenges has been to scale up electrostatic forces, which are very strong at the micro and nano scales, to the centimeter scale needed for power clothing. We have been able to do this by incorporating a very small amount of special fluid — called a liquid dielectric — to amplify the forces.
Tech Briefs: How does the pressure that can be generated by these pumps compare to a conventional motor-driven pump? Are you thinking about how to power them?
Prof. Rossiter: Our Electro-Pneumatic pump uses much less power than a motor-driven of the same volume, and yet delivers about the same amount of air. We can easily stack them to create larger pressures and flow rates. We envisage an array of small soft pumps distributed across the clothing to deliver assistance precisely where it is needed, like at the hip or the ankle. The Electro-Pneumatic pump uses higher voltages, but lower currents, than motor-driven pumps, so we are developing small electrical power converters to link portable batteries and the pumps.
Tech Briefs: Why is it so important to make the electro-pneumatic pumps smaller and smaller?
Prof. Rossiter: Smaller pumps are easier to configure for a wider range of power clothing. It is generally better to have a larger number of small pumps than one large one. It also makes the system more robust to failure. If one small pump fails, the others can share the load.
Tech Briefs: What is the most exciting application that you envision with this pump?
Prof. Rossiter: Power clothing! As we get older we will all need assistance to move around. I see assistive clothing driven by our new soft pumps as a great boon to independence, quality of life and happiness.
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