The effort to integrate molded parts and electrical circuitry is as old as injection molding itself.
Eugen and Karl Hehl built their first injection molding machine in 1954 to protect electrical connectors in camera flash bulbs from corrosion. Later, molders used two-component molding and hot stamping to produce molded interconnect devices or MIDs. A modern concept employs lasers to activate electrical circuits on specially compounded plastics.
Now comes a candidate from the world of genetic engineering. And if it can be made into a commercial process, it’s a doozy, particularly for medical applications where use of electronic sensors is booming.
Researchers at the University of Massachusetts Amherst say they have genetically designed a new strain of bacteria that spins out extremely thin and highly conductive wires made up solely of non-toxic amino acids.
“New sources of electronic materials are needed to meet the increasing demand for making smaller, more powerful electronic devices in a sustainable way,” says researcher Derek Lovley. Potential applications include biocompatible sensors, computing devices and as parts of solar panels.
The basis of the technology is the Geobacter, a common microorganism that secretes electrically conductive protein filaments.
“As we learned more about how the microbial nanowires worked we realized that it might be possible to improve on nature’s design,” says Lovley. “We knew that one class of amino acids was important for the conductivity, so we rearranged these amino acids to produce a synthetic nanowire that we thought might be more conductive.
“We designed a synthetic nanowire in which a tryptophan was inserted where nature had used a phenylalanine and put in another tryptophan for one of the tyrosines. We hoped to get lucky and that Geobacter might still form nanowires from this synthetic peptide and maybe double the nanowire conductivity.
“We were blown away by this result,” says Lovley. The conductivity of biowire exceeds that of many types of chemically produced organic nanowires with similar diameters. The extremely thin diameter of 1.5 nanometers (over 60,000 times thinner than a human hair) means that thousands of the wires can easily be packed into a very small space.
This research was supported by the Office of Naval Research and the National Science Foundation’s Nanoscale Science and Engineering Center