Nov 27 2023

Hybrid Biopolymer Transistors – Implications for Brain Machine Interface

There are several technologies which seem likely to be transformative in the coming decades. Genetic bioengineering gives us the ability to control the basic machinery of life, including ourselves. Artificial intelligence is a suite of active, learning, information tools. Robotics continues its steady advance, and is increasingly reaching into the micro-scale. The world is becoming more and more digital, based upon information, and our ability to translate that information into physical reality is also increasing.

Finally, we are increasingly able to interface ourselves with this digital technology, through brain machine interfaces, and hybrid biological technology. This is the piece I want to discuss today, because of a recent paper detailing a hybrid biopolymer transistor. This is one of the goals of computer technology going forward – to make biological, or at least biocompatible, computers. The more biocompatible our digital technology, the better we will be able to interface that technology with biology, especially the human brain.

This begins with the transistor, the centerpiece of modern computing technology. A transistor is basically a switch that has two states, which can be used to store binary information (1s and 0s). If the switch in on, current flows through the semiconductor, and that indicates a 1, if it is off, current does not flow, indicating a zero. The switch is also controlled by a gate separated by an insulator. These switches can turn on and off 100 billion times a second. Circuits of these switches are designed to process information – to do the operations that form the basis of computing. (This is an oversimplification, but this is the basic idea.)\

This new hybrid transistor uses silk proteins as the insulator around the gates of the transistor. The innovation is the ability to control these proteins at the nano-scale necessary to make a modern transistor. Using silk proteins rather than an inorganic substance allows the transistor to react to its environment in a way that purely inorganic transistors cannot. For example, the ambient moisture will affect the insulating properties of these proteins, changing the operation of the gates.

These hybrid transistors can function in one of two modes. One is a traditional mode, by which an electrical field turns the switch either on or off (allows current to flow or not). But also these transistors can function in a completely separate mode, where the switch is turned on or off based upon the morphology and biochemistry of the organic silk-protein layer. This allows the transistor to respond to the environment.

To illustrate this principle, the researchers created a breath sensor which can detect and measure the humidity level in air breathed across it. The authors write that this feature allows the combination of the performance of standard silicon computer chips with the functionality of a biopolymer. This allows for a reconfigurable platform, one that can interact with its environment, including biology.

As always, it is difficult to predict how any one specific technology will pan out in the future. I don’t know if silk protein transistors will be big one day. It is easier to make predictions about a type of technology – transistors that are either entirely biological or a hybrid of biological and inorganic components. Bio-hybrid computer technology, as the authors say, allows for new possibilities. It may simply turn out to be another option with specific applications.

The hope is, however, where this technology might lead, and that is a more and more seamless integration of computer technology with biology, and specifically (but not limited to) the human brain. I have written before about this. We already can interface brain activity with computer chip function, through electrodes place on or near the brain. All cells are electrical, and brain cells are specialized to use electrical signals to store and process information. They are, in a way, biological computers. Efforts are underway to make computers function more like brains, and to interface the two.

The end-stage of this technology is something like the Matrix – all inputs and outputs from the brain can go from and to a computer. If you have complete control over those inputs and outputs, you can essentially replace external physical reality with a virtual reality – the Matrix. But along the way, there are lots of potentially powerful things you can do, and we have already begun.

The ability to insert a computer chip into the brain that can react to brain states and alter brain states can, for example, stop a seizure from progressing. It can suppress the tremor of Parkinson’s disease. These things are already essentially happening, but the better the interface, the more powerful the control. We are likely to see an increasing number of such clinical applications, using a brain-machine interface to treat a host of neurological diseases and disorders. This is a new paradigm of treatment. Instead of using chemistry to alter the biochemistry of the brain, we can use electrical and/or magnetic stimulation to alter the electrical function of the brain. This approach is potentially more powerful than the chemical (drug) approach, and is not limited by the inherent specificity limitations of biology. We can only make drugs that act on existing receptors, and those receptors have only so much specificity (hence side effects). But there is no theoretical limit to the specificity of activating a single circuit or even neuron – only technical limits.

Beyond patching brain disorders, more sophisticated technology can allow for the replacement of lost function, such as controlling a robotic prosthetic for a missing body part, or replacing a lost sense such as vision or hearing. Again, we are at the early stages of this technology already.

As we keep going, we get beyond treating maladies to enhancing function. At present this is just science fiction, but it is a direct extrapolation of current technology. Biological or hybrid computer components, ones that are increasing biocompatible and able to function for extended periods, could theoretically be used to replace or augment any neurological function. The mature version of this technology might be a computer-based “third hemisphere” of the brain, interfacing seamlessly with the other two, adding to and augmenting your cognitive function.

Imagine if everyone (or some ones) were also a supercomputer, with all the functionality that implies. They could communicate to each other wirelessly, and to the cloud of information and virtual existence. That would fundamentally change the nature of human existence.

OK, that is a long trip from a computer chip with silk proteins, but that is where all of this is very deliberately headed. There are no theoretical limitations here, and no fundamental breakthroughs needed (although there likely will be breakthroughs). Steady incremental advances in computer, AI, and biocompatible technology is all that is needed, and we are already on our way.


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