Diodes and resistors could be assembled from proteins by quantum physics

Written By O. Love

As part of a pilot study, scientists have created self-assembling circuits based on proteins that can perform simple logical functions. The work demonstrates the possibility of creating stable digital circuits that use the properties of an electron on a quantum scale.

One of the stumbling blocks in the creation of molecular circuits is that as the size of the circuit decreases, they become unreliable. This is because the electrons needed to create the current behave like waves at the quantum level, not like particles. 

For example, in a circuit with two wires one nanometer apart, an electron can “tunnel” between the two wires and actually be in both places at the same time.

Kyōchi and co-author Xingkai Qiu of the University of Cambridge built the new circuits by first placing two different types of fullerene cells on patterned gold substrates.

They then immersed the structure in a solution of photosystem one (PSI), a widespread chlorophyll protein complex.

Various fullerenes induced PSI proteins to self-assemble on the surface in certain orientations, creating diodes and resistors after depositing top contacts from the liquid gallium-indium metal eutectic EGaIn on them.

This process simultaneously eliminates the shortcomings of single-molecule compounds and preserves the molecular-electronic function.The researchers coupled self-assembling protein assemblies with human-made electrodes and created simple logic circuits that used electron tunneling behavior to regulate current.

The researchers created simple diode-based AND/OR logic gates from these circuits and incorporated them into pulse modulators that can encode information by turning one input signal on or off depending on the voltage at another input.

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