Date: Apr 15, 2009 Author: Joan Zimmermann Source: MDA (
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by Joan Zimmermann/jzimmermann@nttc.edu
Inkjet printing has revolutionized the photo business, to where it is now trivial to produce clear, glossy photos with your home printer. Now, a simple inkjet technique developed by NanoSonic, Inc. (Blacksburg, VA), may offer hope to electronics makers seeking faster, simpler, more environmentally friendly methods for producing circuitry.
The NanoSonic technique uses several different inks that include low- and high-resistance materials to deposit circuit traces with a conventional inkjet printer. Typically, printing of circuit boards relies upon a multistep process that involves toxic metals such as lead, and organic solvents such as trichloroethylene.
The secret to NanoSonic's approach is in its electrostatic self-assembly (ESA) technique, which has been funded through MDA Phase I and Phase II SBIRs to develop missile electronics, and nonlinear optical thin films for optical communications.
ESA can be used to precisely build stacks of highly uniform, nanometer-thick layers, like bone builds itself upon its scaffold. NanoSonic has produced a library of more than 2,000 materials, including polymers; metal and oxide nanoclusters; and complex molecules such as "buckyballs." Proteins and other biological molecules can also be constructed using ESA.
NanoSonic can precisely control the placement of the building blocks of these materials, as well as the order of the molecular layers, allowing control over electrical, optical, magnetic, thermal, mechanical, and other properties, important to many engineering devices and applications. In experiments for its circuit board applications, NanoSonic first used a complicated laboratory printer, but has since graduated to a modified inexpensive desktop printer.
MDA's interest in ESA techniques for circuitry applica-tions dates back to the late 1990s. It then awarded a Phase II SBIR to further develop NanoSonic's self-assembling materials for manufacturing next-generation radio frequency (RF) and microwave device components onto flexible substrates using low-cost inkjet print self-assembly methods. Through that continuing Phase II MDA project, NanoSonic developed the capability to inkjet print metal nanocluster solutions onto substrates to form patterned, electrically conductive lines at room temperature. Effectively, says NanoSonic founder and CEO Richard Claus, "this means that you can use a desktop printer with cartridges containing ‘special' ink to print the conductive traces for electronic circuits," or for MDA's purposes, advanced electronic devices. Inkjet deposition of metals at room temperature was an important step. Room-temperature printing enables printing on plastics that would otherwise melt at high temperature, compared with traditional methods of deposition that may require heating the ink.
With other government grants, NanoSonic parlayed the ESA technique into a material called MetalRubber™, a substance that can conduct electricity as well as copper wire can, but with a fraction of the metal content. It can be stretched to 1,000 percent of its size and snap back to its original shape with no loss of properties, heated to over 700ºF, and endure acetone or jet- fuel baths with impunity. MetalRubber has multiple abilities all in one material: conductivity; elastic modulus; thermal properties; and response to specific electromagnetic signals.
While NanoSonic's materials are still in development, ESA technology has ignited the imagination of many future watchers—foldable TV monitors, morphing aircraft wings, and all manner of electronic origami are being considered as possible products. The company sells MetalRubber sensors, and 6- and 12-inch-square sheets of the material. In addition, NanoSonic continues to work closely with multiple partners to develop applications for the technology.
