Positioning miniature microelectromechanical devices in medical applications traditionally relies on a combination of actuators that cause movement and sensors that detect position. Now, the ability to precisely control the position and movement of miniature devices is being taken into new territory with scientists developing tinier and simpler devices without a single sensor. The prototype devices also use a single actuator rather than the several usually required. Having a single actuator enabled the researchers to reduce the size of their devices and also reduce the complexity of the electronics and power supply.

The devices developed by scientists at King Abdullah University of Science and Technology (KAUST; Thuwal, Saudi Arabia) are fabricated from a wafer of silicon on an insulator, with final dimensions of 2 by 2.5 millimeters width and just 0.4 millimeters thick. The simplicity of the design in being constructed from a single wafer of material is another significant innovation: alternative devices generally require several distinct parts. The scientists developed and tested several versions of their devices and were pleased with the promising results.

They demonstrated that applying a suitable voltage can switch the mobile section through a series of fixed positions a mere 10 micrometers apart. This would carry whatever component was being positioned in a real-world application. A row of serrated catches and grippers on either side of the moving part holds it in stable positions without the need for any sensors. Changing the voltage can return the system to its original configuration.

The scientists believe that the performance demonstrated by their prototypes could one day be used to precisely control miniature surgical instruments, allowing extremely fine techniques not currently possible. Or it might be used to deliver drugs at very precise locations and times. They hope it might also find applications in many areas of industry where miniaturization and microdevices are taking technology to ever lower scales.

“The devices can be implemented in very narrow spaces without adding the congestion that might be involved using alternative methods,” said Hossein Fariborzi, professor of electrical engineering. “Because of the simple design and control, we can remove direct electrical connections and enable remote activation and thereby greatly increase the flexibility of this microsystem for use in various applications.”

“Our novel approach gets rid of sensors,” explained postdoc Hussein Hussein. “The basic design could be easily adjusted to fit any application and put it into practice.”

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