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Phone Sensors Could Meld with Human Body

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Microscopic sensors and motors in smartphones detect movement, and could one day help their cameras focus. Now scientists have devised components for these machines that are compatible with the human body, potentially making them ideal for use in medical devices such as bionic limbs and other artificial body parts, researchers say.

The technology is called microelectromechanical systems, or MEMS, and involves parts less than 100 microns wide, the average diameter of a human hair. For example, the accelerometer that tells a smartphone if its screen is being held vertically or horizontally is a MEMS sensor; it convert signals from the phone's environment, such as its movement, into electrical impulses.

MEMS actuators, which may focus your next smartphone's camera, work in the opposite way, by converting electrical signals into movement.

MEMS are typically produced from silicon. But now researchers have devised a way to print highly flexible parts for these micro-machines from a rubbery, organic polymer more suitable for implantation in the human body than is silicon. [7 Cool Uses of 3D Printing in Medicine]

The new polymer is attractive for MEMS because of its high mechanical strength and how it responds to electricity. It is also nontoxic, making it biocompatible, or suitable for use in the human body.

The method the scientists used to create MEMS components from this polymer is called nanoimprint lithography. The process works much like a miniaturized rubber stamp, pressing a mold into the soft polymer to create detailed patterns, with features down to nanometers, or billionths of a meter, in size. The scientists printed components just 2 microns thick, 2 microns wide and about 2 centimeters long.

"The printing actually worked, that is to say that we were able to get the recipe right," researcher Leeya Engel, a materials scientist at Tel Aviv University in Israel, told LiveScience. "Fabrication at small scales is a very tricky business, especially when using new materials."

The fact that nanoimprint lithography does not rely on expensive or cumbersome electronics makes the new process simple and cheap.

"The use of new, soft materials in micro-devices stretches both the imagination and the limits of technology, but introducing polymer MEMS to industry can only be realized with the development of printing technologies that allow for low-cost mass production," Engel said.

Scientists have previously created biocompatible MEMS parts, Engel noted, but her team's method offers an advantage: it can manufacture these biocompatible parts quickly and inexpensively.

"Other methods, especially when you want to reduce the scale below a micron, can get very expensive and take a long time," Engel said.

For example, using an electron beam to create a large array of MEMS parts "might take running the machine all night, which is very costly," Engel said. "The process we reported took about 15 minutes."

As a bonus, MEMS parts made from this organic polymer are highly flexible; they may be hundreds of times more flexible than such components made from conventional materials. This flexibility could make, for example, MEMS sensors more sensitive to vibrations and MEMS motors more energy efficient, leading to better cameras and smartphones with longer battery lives.

The researchers now plan to manufacture functional devices constructed nearly entirely out of the polymer.

"If the printing processes really do allow for mass production of polymer devices, then we will be looking at the possibility of devices so cheap that they can even be disposable," Engel said.

"I think that printing processes are the technology of the future," Engel added. "It will take a bit more tweaking, but I do believe that one day it will be possible to mass-produce sophisticated sensors and actuators made of organic materials using printing."

The researchers cautioned they have not yet implanted devices based on this technology in humans, "although our technology might enable this," Engel said.

The scientists will present their findings Sept. 19 at the International Conference on Micro and Nano Engineering in London.

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