Spiral Scanning And Encased Cantilevers For High Spatial And Temporal Resolution In Atomic Force Microscopy

Atomic Force Microscopy in vacuum readily achieves atomic resolution however imaging in fluid has substantially lower resolution due to the damping of the cantilever by the fluid. We reduced the damping and force noise of the probe by building a protective encasement around the cantilever which keeps the cantilever dry but allows the tip to probe the sample in solution. The substantially lower viscosity of the air leads to orders of magnitude improvement in force noise. Furthermore, encased cantilevers retain high resonance frequencies and Q factors when immersed in liquid such that they are thermally limited even at high stiffness. This enables high resolution imaging and force spectroscopy on all commercial AFM systems in liquid. Raster scanning is not ideal for high speed AFM. Less than half of the scan time is used to create an image because trace and retrace can not be interlaced due to piezo hysteresis. Furthermore, the scanner resonance distorts triangular waveforms or requires sinusoidal scanning, where images are rendered from even less than half of the scan time. using advanced image processing tools, such as Inpainting, enables image rendering from 100% of the scan time and use of scan waveforms that best match the inertial limits of the scanner. We have also developed a Z piezo with over 300 kHz bandwidth enabling high scan speeds frame rates. Spiral scanning together with encased cantilevers will lead to significant advances in temporal and spatial resolution for soft biological samples imaged by Atomic Force Microscopy.