Single Actuator System Provides Sensorless Precision Control of Miniature Surgical Instruments – Surgical Techniques


Image: New miniature microelectromechanical devices could find medical applications (Photo courtesy of KAUST)

Positioning of miniature microelectromechanical devices in medical applications traditionally relies on a combination of actuators that cause movement and sensors that detect position. Today, the ability to precisely control the position and motion of miniature devices is being taken into new territory with scientists developing smaller, simpler devices without a single sensor. Prototype devices also use a single actuator rather than several usually required. Having a single actuator allowed the researchers to downsize 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 silicon wafer on an insulator, with final dimensions of 2 x 2.5 millimeters wide and only 0.4 millimeters thick. The simplicity of the design by being constructed from a single wafer of material is another significant innovation: alternative devices typically require multiple separate parts. The scientists developed and tested several versions of their devices and were pleased with the promising results.

They demonstrated that the application of an appropriate voltage can switch the moving section through a series of fixed positions only 10 micrometers apart. This would carry any component positioned in a real world application. A row of latches and serrated clamps on either side of the moving part hold it in stable positions without the need for 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, enabling extremely fine techniques currently not possible. Or it can be used to deliver medication to very specific places and times. They hope it could also find applications in many areas of industry where miniaturization and microdevices are taking technology to ever lower scales.

“Devices can be implemented in very tight spaces without adding the congestion that might be involved using alternative methods,” said Hossein Fariborzi, professor of electrical engineering. “Due to the simple design and control, we can eliminate direct electrical connections and allow remote activation and thus greatly increase the flexibility of this microsystem for use in various applications.”

“Our new approach gets rid of the 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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