Biologic – biofilm for active materials

I have often advocated bio-inspired and biomimetic design, and at the extreme end of that spectrum lies biomaterials—new materials built from biological products or organisms.

A group from the MIT Tangible Media Group are exploring one such material which they term ‘biologic’.

Using a microbe discovered centuries ago in Japan, they are creating hybrid fabrics that respond to humidity. The Natto bacteria expands when the air is humid, making it a naturally evolved “nonactuator”.

The team has done remarkable work to incorporate these living microorganisms into a hybrid “biofilm”, which can be fabricated in configurations to perform useful behavior (e.g., to allow more air flow for cooling). They have also worked out methods for actually building these ideas. (A glance at their videos shows just how non-trivial that part truly is.)

This group has adapted ideas for “responsive structures”, which have been used in “origmi” robots, and self-assembling furniture, etc.. In this case, the expansion and contraction of the biofilm is turned into useful work by the origami style folding. Combinations of simple curved and angular bending are used to create structures that change shape in 3D.

The actuation is driven by humidity, so they experimented with techniques for rapidly wetting and drying the film. In principle, these mechanisms should make it possible to control the action of the film.

They also developed an “ink jet” deposition system for fabrication, which is kind of neat. (See the video.)

They have demonstrated some applications.

One is a cute tea bag timer, which has a leaf shaped flag that unrolls as the bag is saturated, indicating when the tea is ready to drink. I didn’t really need this, but it’s really cool!

Another application is “second skin”, which is a garment that opens ventilation holes in response to sweating. In this way, the garment adapts to the activity of the wearer, to help keep cool. The biofilm requires no batteries, and is completely automatic.

Other origami like applications are also possible, items that fold or unfold in response to humidity and heat. They point out that the microbe is food safe, so we could imagine “actuated food”. I’m not sure I’m ready for my fish to start wriggling, but it might be cool to have something like cookies that not lonely look like, say, animals, but actually move!

One thing that isn’t really clear to me is just how rugged this material might be. Does it “die out”? How long does it live? It is sensitive to high heat, soap, or other chemicals?

The latter point is important for use in garments: can I wash it without killing the cool biofilm? Will it die if I leave in the sun, or in a dark drawer, or the freezing luggage compartment of an airliner? What happens if you get caught in the rain, or swim in it? What happens if I dry it over a campfire?

Anyway, well done, all.

  1. Lining Yao,, Jifei Ou, Chin-Yi Cheng, Helene Steiner, Wen Wang, Guanyun Wang, and Hiroshi Ishii, bioLogic: Natto Cells as Nanoactuators for Shape Changing Interfaces, in Proceedings of the 33rd Annual ACM Conference on Human Factors in Computing Systems. 2015, ACM: Seoul, Republic of Korea. p. 1-10.

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