Embedding Transistors in Living Tissue

Last week Nature Materials published a paper by researchers at Harvard and MIT on growing nanoelectronic structures in living tissue. 

To integrate electronics into living tissue, the electronics must have openings within them large enough so as not to interfere with biological processes, and their structure and mechanical properties must be similar to biomaterials.  The Nature Materials article focuses on building wires and FETs using nanoelectronic scaffolds.  The FETs can amplify measurements of conductivity in very precise locations.  Nanosensors without this amplification would not provide a high enough signal-to-noise ratio. 

The transconductance of these FETs in is the 3µS range, which is four or five orders of magnitude worse than a macroscopic PCB-mounted FET.  The article gives the impression that the gate threshold voltage of these transistors is much lower than a normal transistor’s, but they do not go into detail on the electrical characteristics.  The potentially useful new element of their research is that the transconductance of the FETs does not vary with FET location or how the network of FETs bends along with the tissue it’s embedded in.  If they can increase the number of FETs per unit volume and work out a way to address them with a MUX/de-MUXing scheme, they could collect 3-D data from sensors in living tissue.  This would allow monitoring individual cells’ response to drugs. 

The nature of this research invites comparisons to science fiction.  That is reasonable to the extent that it’s one example of technology being melded with biological tissue.  It would be interesting to hear if anyone in the medical or biological research professions has any need for a network of sensor embedded in live tissue and providing real-time data localized down to the cellular level or if this is just possible infrastructure for some future technology. 

While researching this article, I noticed the latest edition of Nature has an article about public fear of nanotechnology.  Searching for that, I found many articles on that topic.  This is not surprising because even as a scientifically-minded person, the notion of webs of electronics grown in tissue is unsettling on a visceral level.  What was surprising is that anti-nanotechnology extremists have targeted nano-researchers with bombs. 

The researchers point out this is fueled by hype from researchers themselves promoting their work as revolutionary and by popular articles that repeat those claims and draw analogies to science fiction.  This rings true, but there are also legitimate questions about at what point nanotechnology will find applications in weapons.  This not sucfficient reason, though, to fear the technology itself.

As for the science fiction analogies, if we ever solve the countless problems associated with interfacing technology to the human body, the ability to embedded transistors in tissue could be a one part of it. 

Image is from the Lieber Research Group.     

For Further Reading:

For the moment, non-subscribers to Nature can find the article on the research group’s website. 

Cabe Atwell commented briefly on this research last week.