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Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) enables the characterization of individual biological molecules through the application of mechanical force. The spatiotemporal resolution of such measurements depends greatly on the AFM cantilever that is used, specifically its stiffness, hydrodynamic drag, and material composition. Prior work has shown that focused ion beam (FIB) lithographic modification of small cantilevers can be used to lower the spring constant (and thus force noise) and drift while maintaining a relatively fast time response. Published methods for implementing such optimization rely on specific FIB instruments and cantilever types, limiting broad implementation of these methods to improve SMFS data quality. Here, we show that it is possible to achieve such optimized properties using generalized techniques applicable to a broader array of FIB instruments and starting from new types of cantilevers that are presently commercially available. Modified cantilevers exhibited a 90% reduction in spring constant, sub-pN force drift to tens of seconds, and a time response of ∼25 μs in the liquid environment relevant to biological measurements.
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Hollow Atomic Force Microscopy Cantilevers with Nanoscale Wall Thicknesses
Abstract In atomic force microscopy, the cantilever probe is a critical component whose properties determine the resolution and speed at which images with nanoscale resolution can be obtained. Traditional cantilevers, which have moderate resonant frequencies and high quality factors, have relatively long response times and low bandwidths. In addition, cantilevers can be easily damaged by excessive deformation, and tips can be damaged by wear, requiring them to be replaced frequently. To address these issues, new cantilever probes that have hollow cross‐sections and walls of nanoscale thicknesses made of alumina deposited by atomic layer deposition are introduced. It is demonstrated that the probes exhibit spring constants up to ≈100 times lower and bandwidths up to ≈50 times higher in air than their typical solid counterparts, allowing them to react to topography changes more quickly. Moreover, it is shown that the enhanced robustness of the hollow cantilevers enables them to withstand large bending displacements more readily and to be more resistant to tip wear.
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- Award ID(s):
- 1845933
- PAR ID:
- 10361039
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small
- Volume:
- 17
- Issue:
- 51
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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