Researchers have developed self-assembled, protein-based circuits that can do simple logic functions in proof-of-concept research. The work demonstrates that it is possible to develop stable digital circuits that benefit from an electron’s properties at quantum scales.
Molecular circuits
One of the stumbling blocks in developing molecular circuits is that the circuits become unreliable as the circuit size lowers—the electrons required to create current act like waves, not particles, at the quantum scale. On a circuit with two wires that are one nanometer apart, the electron can “tunnel” in between the two wires and efficiently be in both places concurrently, making it challenging to control the current direction. Molecular circuits can minimize these problems, but single-molecule junctions are short-lived or low-yielding due to difficulties associated with making electrodes at that scale.
” Our objective was to try and create a molecular circuit that utilizes tunneling to our benefit, instead of fighting against it,” states Ryan Chiechi, associate professor of chemistry at North Carolina State University and co-corresponding author of a paper explaining the work.
Chiechi and co-corresponding author Xinkai Qiu of the University of Cambridge built the circuits by first placing two kinds of fullerene cages on formed gold substrates. Afterward, they immersed the structure into a photosystem one (PSI) solution, a typically utilized chlorophyll protein complex.
The different fullerenes caused PSI proteins to self-assemble on the surface in certain orientations, producing diodes and resistors as soon as top-contacts of the gallium-indium liquid metal eutectic, EGaIn, are printed on top. This process both addresses the downsides of single-molecule junctions and protects molecular-electronic function.
” Where we wanted resistors, we patterned one sort of fullerene on the electrodes upon which PSI self-assembles, and where we wanted diodes, we patterned another kind,” Chiechi claims. “Oriented PSI remedies current– signifying it only permits electrons to flow in one direction. By controlling the net orientation in ensembles of PSI, we can determine just how charge flows via them.”
Circuit development
The scientists combined the self-assembled protein sets with human-made electrodes and made straightforward logic circuits that utilized electron tunneling behavior to modulate the current.
” These proteins spread the electron wave function, moderating tunneling in manner ins which are still not fully understood,” Chiechi states. “The result is that in spite of it being 10 nanometers thick, this circuit works at the quantum level, operating in a tunneling regime. Furthermore, because we are using a team of molecules instead of single molecules, the structure is stable. We can print electrodes on top of these circuits and construct devices.”
The researchers developed simple diode-based AND/OR logic gates from these circuits. They included them in pulse modulators, which can encode information by changing one input signal on or off, relying on the voltage of another input. The PSI-based logic circuits could switch a 3.3 kHz input signal– which, while not similar in speed to modern logic circuits, is still one of the fastest molecular logic circuits reported to date.
” This is a proof-of-concept rudimentary logic circuit that depends on diodes and resistors,” Chiechi says. “We have shown here that you can build durable, integrated circuits that work at high frequencies with proteins.
” In terms of immediate utility, these protein-based circuits could lead to the development of electronic devices that improve, supplant, and/or extend the functionality of classical semiconductors.”
The research appears in Nature Communications. Co-authors Chiechi and Qiu were previously at the University of Groningen, the Netherlands.
Read the original article on Science Daily.
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