Biological Silk-Based Hybrid Transistors: A New Era in Technology

Researchers at Tufts University’s Silklab have pioneered the use of biological silk as an insulating component in transistors. This innovation enables these devices to interact with their surroundings in a manner akin to living organisms. Such hybrid transistors are capable of identifying various substances and environmental conditions, potentially transforming health monitoring and computational technology. By manipulating the ionic composition of the silk insulator, these devices can adaptively process information, akin to the mechanisms of analog computing. This significant advancement in microprocessor technology could pave the way for self-adaptive microprocessors and novel interfaces between electronic devices and biological systems.

Transistors at the microprocessor scale are now able to sense and react to biological and environmental factors.

Consider the more than 15 billion miniature transistors in your smartphone’s microprocessor chips. These components, traditionally made from silicon, metals like gold and copper, and insulators, convert electric currents into digital signals for data communication and storage. These materials are fundamentally inorganic, originating from minerals and metals.

Imagine, however, the possibility of creating these essential electronic components with partial biological characteristics, enabling them to directly respond to environmental changes and mimic living tissues.

Innovations at Tufts University’s Silklab

This vision was realized by the team at Tufts University Silklab, who replaced the conventional insulating materials in transistors with biological silk. Their groundbreaking work was published in the journal Advanced Materials.

Silk fibroin, the primary structural protein in silk fibers, can be accurately deposited on surfaces and chemically or biologically modified to alter its properties. Silk, when modified in this way, can detect a broad range of substances from both the human body and the environment.

These hybrid biological transistors can alter their electronic behavior in response to various gases and molecules in their surroundings.

Applications in Health Monitoring

The team’s initial demonstration involved using these hybrid transistors in a highly sensitive, rapid-response breath sensor capable of detecting humidity changes. Future adaptations of the silk layer could enable the detection of certain cardiovascular and pulmonary diseases, sleep apnea, carbon dioxide levels, and other diagnostic gases and molecules in breath. When applied to blood plasma, they might provide vital information about oxygenation, glucose levels, circulating antibodies, and more.

Even before developing these hybrid transistors, the Silklab, under the leadership of Fiorenzo Omenetto, Frank C. Doble Professor of Engineering, had utilized fibroin in creating bioactive inks for environmental and bodily sensing fabrics, under-skin or dental health monitoring tattoos, and pathogen-detecting sensors.

Explaining Hybrid Transistor Mechanics

A transistor essentially acts as an electrical switch, with metal leads for electrical input and output, separated by a semiconductor material which conducts electricity under certain conditions.

The gate, insulated from other components, functions as the switch’s control mechanism. It activates the transistor when a specific threshold voltage creates an electric field across the insulator, initiating electron movement in the semiconductor and allowing current to flow through the leads.

In biological hybrid transistors, a silk layer serves as the insulator. When this silk absorbs moisture, it forms a gel carrying various ions. The gate activates the transistor by rearranging these ions in the silk gel. Altering the silk’s ionic content changes the transistor’s operation, allowing activation by a range of gate values.

The Future of Computing and Biological Integration

According to Omenetto, this development introduces the possibility of merging biology with computing within modern microprocessors. “Imagine creating circuits that process variable information, akin to analog computing, influenced by changes in the silk insulator,” he said. The greatest known biological computer, the human brain, processes information using variable levels of chemical and electrical signals.

The challenge was creating hybrid biological transistors at a nanoscale, as fine as 10nm or less than 1/10000th the diameter of human hair. “Now that we’ve achieved this, we can produce hybrid transistors using the same methods as commercial chip manufacturing,” said Beom Joon Kim, a postdoctoral researcher.

Billions of transistor nodes, reconfigurable through biological processes in silk, could lead to microprocessors resembling neural networks in AI. Omenetto envisions circuits that self-train, respond to environmental cues, and directly record memory, expanding the boundaries of computing.

Future possibilities include devices that detect and respond to complex biological states and the development of large-scale analog and neuromorphic computing. Omenetto remains optimistic about future advancements in this field, foreseeing significant fundamental discoveries and applications at the intersection of electronics and biology.

Reference: “Bimodal Gating Mechanism in Hybrid Thin-Film Transistors Based on Dynamically Reconfigurable Nanoscale Biopolymer Interfaces” by Beom Joon Kim, Giorgio Ernesto Bonacchini, Nicholas A. Ostrovsky-Snider and Fiorenzo G. Omenetto, 28 August 2023

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More about biological silk transistors

• Tufts University Silklab
• Biological silk in electronics
• Health monitoring advancements
• Silk fibroin applications
• Hybrid transistors research
• Analog computing and biology integration
• Advanced Materials journal publication