When you cut yourself, you bleed, then clot, and finally heal. But if you drop your phone, only tech service can help -- if you are lucky!
Could our phones someday heal themselves? Could the delicate electronic structures hidden inside grow in much the same way your skeleton formed itself, responding only to the steering messages of the chemical environment in our bodies?
Researchers at MIT have just demonstrated a big step forward in designing living materials. They started with E. coli, a bacteria that grows a biofilm of what are cutely called "curli fibers". Normally E. coli grows these curli fibers to help it attach to surfaces.In this case, the scientists engineered the E. coli to produce curli fibers only when a special trigger molecule is present. This allows the scientists to use the trigger molecule as a switch to turn curli fiber production on or off. They designed two variations on this: one responding to a trigger called AHL and the other responding to a trigger known as Tc.
"Ultimately, we hope to emulate how natural systems, like bone, form. No one tells bone what to do, but it generates a material in response to environmental signals", says Timothy Lu, an assistant professor of electrical engineering and biological engineering and senior author of the paper describing the team's work in Nature Materials
The bacteria triggered by Tc grow curli fibers with an amino acid, histidine, built in. The histidine will naturally pick up gold nanoparticles in the environment. The bacteria triggered by AHL have no histidine tags. By varying the concentrations of AHL and Tc, the scientists can create a biofilm laced by rows of gold nanowires, creating a network that conducts electricity.
By further engineering some bacteria that produce the trigger molecules, the scientists also demonstrated that "cells can coordinate with each other to control the composition of the biofilm." This is a first small step towards creating a system that could recognize a deficiency and react to repair itself, not as a conscious process such as the phone tech would use to diagnose and repair, but as a natural consequence of maintaining balance in the "organism" that is a hybrid of cells and engineered materials.
Additional experiments explored creating biofilms with a mixed system of gold particles and quantum dots.
Of course, if we own products based on genetically engineered organisms, we will have to evaluate and control the risks of those unnatural living cells spread widely throughout our environment. Using bacteria for production but releasing only the finished product (without any living organisms remaining in it) would be a safer first step, containing genetically engineered organisms in a limited environment where they can be better controlled. But to create products that would truly be self-healing would presumably require those products to exist as living systems in the hands of consumers.
While I would rather have GE in my phone than in my food, we still have a long way to go to understand the risks of these new technologies and manage them properly. But if the power of nature could help us harness materials to replace fossil fuels with solar power or design scaffolds for replacement organs, it may be a risk worth managing.