Atomic force microscope on-a-chip

February 17, 2017 // By Julien Happich
By leveraging a readily available Silicon-On-Insulator MEMS manufacturing process (with the help of MEMS-foundry MEMSCAP), researchers at the University of Texas at Dallas have designed the fully actuated probe stage of an Atomic Force Microscope (AFM) on a single chip measuring only a few millimetres square.

Additional driving circuitry, an external signal conditioning board and a few stepper motors (to approach the samples) are all what would be needed to build a fully functional AFM possibly orders of magnitude simpler and cheaper than today's bulkier solutions.

Their paper "On-Chip Dynamic Mode Atomic Force Microscopy: A Silicon-on-Insulator MEMS Approach" published in the Journal of Microelectromechanical Systems details the fabrication and characterization of such a MEMS-based AFM probe-scanner

The main novelty is that rather than relying on the deflection of a laser beam on the back of a micro-cantilever to monitor the AFM's tip position, here the MEMS probe-stage integrates not only X-Y electrostatic actuators for scanning a sample but also a piezoelectric layer able to both actuate the micro-cantilever out-of-plane and senses its deflection. Thanks to this integrated piezoelectric feedback loop, the intricate three-degree-of-freedom design can be operated in tapping-mode, yielding topographic AFM images with an imaging range of up to 8×8μm.

The fabricated MEMS probe scanner, with close-up SEM images highlighting major components of the device.