The long-term objective of this proposal is to develop high performance atomic force microscope (AFM) cantilevers for application to biomedical research. The AFM is emerging as a powerful tool for biomedical research, and has found applications that include imaging of DNA, measuring local surface electrostatics on membranes, mapping mechanical properties of cells and single molecule protein mechanics. It is also considered a central enabling technology in nanotechnology. One of the limiting elements in current AFMs is the cantilever. The performance of a cantilever is primarily characterized by a combination of spring constant and resonance frequency. We propose to develop new cantilevers with resonance frequencies in the range 1-100 MHz in solution, for cantilevers with a spring constant of 0.1 N/m. This resonance frequency is approximately one to three orders of magnitude better than the best cantilevers that are currently available. The new cantilevers will be constructed by two independent methods, focused ion beam milling of conventional silicon or silicon nitride cantilevers and electron beam deposition. Cantilevers with leg a thickness of 100 nm or less will and widths of 100 nm or less will be milled using an ion beam from the material at the end of a conventional cantilever, producing a compound cantilever with a small high performance cantilever at the free end of the larger one. Similar compound cantilevers will be constructed by electron beam deposition plastic like nanostructures in the shape of small cantilevers. Among other things, these new cantilevers will allow faster scanning, increase the temporal resolution of force measurement, improve measurement sensitivity by reducing cantilever noise, and improve sensitivity by reducing cantilever spring constant. To use these new cantilevers, we propose to construct an AFM head with appropriate optics to work with very small cantilevers and position sensor with data acquisition system with a detection bandwidth of at least 100 MHz. This detector will be used to characterize physical properties of the new cantilevers. In addition, we will test the performance of the new cantilevers in electrostatic mapping experiments where we expect improve sensitivity and a bilayer fusion experiment in which we expect to uncover new dynamics lipid rearrangement during fusion.
| Kumar, S; Hoh, J H (2001) Probing the machinery of intracellular trafficking with the atomic force microscope. Traffic 2:746-56 |
