Re-Defining the Concept of Printing: Mass Producing 3-Dimensional Micro Scale Machines

A Redwood City, California, company has developed a new technique for building micro-scale machines layer by layer, using a "printer" supplied with specially formulated "inks" containing materials from metals to ceramics to polymers. Various micro-scale structural features can be built in, including tiny passages and chambers. This Technology Review story goes into more detail:

Each layer is cured by a flash of ultraviolet light before the next layer is printed, and once all of the layers have been printed, the whole assembly is fired at high temperatures, about 850 degrees Celsius , depending on the materials used. These materials have to be carefully selected so that they shrink at the same rate during the firing, and so that the space-holding materials can diffuse through the other materials, leaving behind empty spaces.


One of the company's first devices, a fuel-cell "reformer" for stripping hydrogen from methanol, will supply enough hydrogen for micro fuel cells that recharge 20-watt two-way radios used in emergency areas, where grid power isn't reliably available. The 300-layer device shows the complexity possible with the printing technique, Chait says. The layers form a total of 33 discrete components, such as heating coils, catalyst beds, "chambers, passageways, a diffuser section, a reformer section, and a combustion section," he says. Methanol is fed into the device, and the combination of steam and catalysts free the hydrogen. The entire reformer is the size of two dominoes.
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Chait says his company is working with several others to create prototype devices based on the new technique, which can produce complex, three-dimensional structures out of multiple materials--and do so in a high-throughput process that can lower costs. The new method is an improvement over other printing-based techniques, Chait says, such as those that print designs on pre-formed ceramic sheets. The new method requires no pre-forms, which simplifies the process, cuts costs, and allows for more-complex designs, he says.


EoPlex is applying the concept to manufacturing micro-reactors, devices now often made from silicon, which quickly combine small amounts of precursor compounds to form high-value chemicals. Because they work with small amounts of chemcials at a time, such micro-reactors could be safer than conventional techniques when interacting with toxic or volatile chemicals. EoPlex has also designed an electrical generator smaller than a dime that uses piezoelectric materials to transform vibrations in a vehicle into electricity for powering wireless sensors. While wireless air-pressure sensors are now available on luxury cars, Chait says the new power source could lead to much smaller devices. The new printing technique would help make the sensors inexpensive enough to be put on all new cars.


Printing technologies have promise because "they are amenable to low-cost mass production," says Michael Cima, materials-science and engineering professor at MIT. "If you're talking about sensors for cars, you've got to make millions of them, and you've got to make them cheaply." ....

Source.

This technology is even more intriguing than similar silicon micro-scale fabrication methods, due to the use of several different materials together in the same micro-machine. This is a technology to be watched--because this type of process almost inevitably is shrunk in size over time, like silicon lithography for micro-electronics.