A researcher at the University of Warwick’s Centre for Nanotechnology and Microengineering has designed a device – a multi-function Tribological Probe Microscope (TPM) – that is said to deliver measurements of friction, hardness, elasticity and surface shape of high tech materials.
Dr Ping Liu’s Tribological Probe Microscope is able, in one pass, to measure an area of 100 by 100 micrometres of surface and give an accurate measurement of the surface topography (shape), friction, surface elasticity, and hardness. These four simultaneous surface measurements can then be accurately correlated.
The device uses a Berkovich tip with a 100 nanometre radius mounted on a silica rod a few millimetres long, fixed on a thin beryllium/copper foil acting as a flexible spring.
A small permanent magnet, surrounded by a coil, is attached to the other side of the beam. The force with which the tip contacts the sample surface is controlled by passing a current in this coil, which delivers a constant force in a range of 0.01- 30mN.
The tip slides along the sample measuring the shape or topography of the sample surface down to a resolution of 0.1nanometres. At the same time the friction of the surface causes the probe tip to tilt and by measuring the amount of tilt the device is able to get a measure of the surface’s friction properties.
Finally as the tip exerts a downward force the probe is said to record the depth of penetration of the probe as a measure of the surface hardness at that point.
It then records how far the depressed surface recovers to its original shape after the applied force has been removed as a measure of the surface’s elasticity.