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Engineers Combine Biological Energy-Harvesting with Electronic Circuits

The future promises bomb-sniffing dogs on a chip and so much more.
Mitochondria visualized. Image: Cell Signalling Technology

Engineers at Columbia University have, for the first time, successfully plugged an electronic circuit into a biological energy-harvesting system constructed only from raw molecular materials. The advance, described Monday in Nature Communications, offers a new pathway into any number of awesome sci-fi contraptions, from computers that can process biological sensory data, such as smell and taste, to electronics powered by the same things as living cells, e.g. sugar.

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Previous experiments have accomplished similar-sounding schemes—energy harvested within an inner-ear, tree-powered nanoelectronics—but with the critical limitation of requiring actual biological cells. It turns out to be a bit simpler to take an existing unit of biology and plug into some electronics than it is to take molecular raw materials and build your own custom ion-pump machinery.

It's not all that far-fetched to imagine a unification between the evolution-fashioned power plants employed by our cells and the electric charges powering our computers. Our cells store energy in the form of compounds called ATP, which is scooted around from place to place and used in a few different ways. One of those involves the process of ion pumping, in which positively charged ions (like an atomic nucleus without its usual electron cloud) are distributed across a protein membrane, with the result being potential energy stored as a difference in electric charges from one end of the membrane to the other.

It's a bit like storing something at the top of a steep hill, only instead of gravity trying to pull it down, the energy potential (of rolling down the hill/gradient) takes the form of electric charge. The hilltop is positive, the bottom is negative.

Image: Trevor Finney and Jared Roseman/Columbia Engineering

So, by mimicking this setup, you can get an electrical potential at the cost of ATP, which is the same stuff your body uses as energy. This potential is used to move an electric current and, hey check it out, you're harvesting electricity from sugar (ultimately). You can just imagine the original ion gradient as a weird transistor.

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Why not just use a normal transistor?

"Biological systems are good at certain things, silicon chips are good at other things," Ken Shepherd, of Columbia's Bioelectronic Systems Lab and the current study's lead author, told Motherboard in a phone interview. "Ion pumps act like transistors, [and] from an [electronics engineering] perspective they are transistors." These transistors, however, offer an "expanded palette of functionality."

An example would be a bomb-sniffing dog, or, perhaps even better, a cancer-sniffing dog (my example). It's thought that some dogs, with their superior biological noses, are able to pick up slight traces of some compounds given off by tumors, particularly in a patient's urine and-or breath. When it comes to medical diagnostics, it's not too hard to see how it might be advantageous to exclude the actual dog from the laboratory in favor of just the smelling part. (Dogs have better uses in hospitals, after all.)

Other applications have more to do with the process by which living cells harvest energy in the first place. ATP doesn't just cruise around in blood, it occurs within a cell and only within a cell. If you were designing an implantable system meant to exist solely within a single cell, which is perfectly reasonable scale-wise, not having to leave that cell to power up would be a big benefit.

Taking a step back, the system is remarkable just as an example of pure bioengineering—biology that bypasses the whole "living" part of living things. In other words, it's biology based "not on whole living cells, not living plants, not living animals," Shepherd said. "It's just the part you want."