A prototype MEMS-based atomic force microscope (AFS) promises to reduce the complexity and the cost of these devices. The device’s small size also may make it suitable for small-scale operations, such as inspecting silicon wafers for faults.

MEMS-based AFS microscope attached to printed circuit board.  Credit: University of Texas at DallasMEMS-based AFS microscope attached to printed circuit board. Credit: University of Texas at DallasStandard AFS microscopes, which are used to examine material surfaces at nanometer scale, are large, bulky, and expensive. An educational AFS can cost $30,000 to $40,000. A laboratory-quality instrument runs to half a million dollars or more.

The MEMS-based device, developed by a team at the University of Texas at Dallas, is about the size of a dime. It is mounted on a credit-card-sized printed circuit board that contains circuits, sensors, and other miniature components that control the microscope.

Full-sized AFS microscopes use small probes attached to a cantilever arm to explore a surface either by touching the surface with a constant force or by maintaining a constant distance above the sample. The constant-force approach can damage softer materials.

The UT-D team’s device operates in “tapping mode,” which means the cantilever and tip oscillate up and down perpendicular to the sample, and the tip alternately contacts then lifts off from the surface. As the probe moves back and forth across a sample material, a feedback loop maintains the height of that oscillation, ultimately creating an image.

The small size of the MEMS AFS chip lends itself to mass production, potentially reducing cost per chip to a few dollars.

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