Investigation of the Huber effect and its application to micromotors

The micromotor is an extremely small device a few millimetres or less in size. Micromotors in the order of microns are realised by MEMS technology. Important applications in biomedicine include ultrasound probes for blood vessels,1 microrobots for colon intervention,2 smart pills and nanolitre pumps. Other uses include actuators for MOEMS and small variable capacitors. One exciting implication of micromotors is that they can be powered by rectifying mechanical vibrations (Feynman-micromotor3) . MEMS are playing an important role in our daily life as these systems are widely used in optics, communication and information systems, fluidics, biotechnology and medicine, scanning probe microscopes, automobiles and aerospace. There are a number of technical challenges with micromotors, including the need to reduce stiction and increase torque. The precise geometry of the motor is usually tightly coupled to the stiction effect —the sticking of adjacent surfaces after release due to static friction. Piezoelectric, electrostatic and electromagnetic effects have been investigated to produce the electromotive force for the micromotor. However, we propose a micromotor design based on the Huber effect456 , as this will allow a new range of geometries and hence possibilities for managing stiction. To date, there have been no reported attempts at using the Huber effect, and this is possibly due to it being a poorly understood phenomenon. The reason for this is that large motors that utilise the Huber effect are selfdestructive and hence have never been reliably characterised. Such motors are shown to be able to operate from a dc or ac source, and this property may be valuable in some MEMS applications.