This award supports refinement of a new, low mass cantilever for use in atomic force microscopy (AFM), and the related development of a novel scan head. AFM is uniquely capable of producing very high resolution data in real time using samples held in a biological environment. AFM measures the surface structure of samples by the effect of the surface on a small flexible probe, called the cantilever, whose motion is affected by the atomic force exerted by the sample. The effect on the cantilever is measured by deflection of a laser beam using the optical system in the scan head. Biological AFM is typically carried out in water, and the damping of its motion by the water determines the response of the cantilever. Commercially available soft cantilevers are long and experience substantial drag in water; shorter cantilevers experience less drag. Preliminary work has led to a prototype torsion cantilever that is about 20% the length of commercially available cantilevers, and has a resonant frequency in water about an order of magnitude higher than commercially available cantilevers. With the support of this award, the design of the prototype and the fabrication process for making it will both be improved substantially. To facilitate use of the new tip in combination with other measurement tools, such as the patch clamp, the PI will also develop a smaller scan head. This will permit simultaneous use of a standard optical microscope, required for the patch clamp procedure, in combination with the AFM. The size reduction will be accomplished by use of a GRIN lens; the optical properties of such lenses derive from the structure of the glass used in its construction, rather than from the shape of the lens as with standard lenses. The GRIN lens will act as the cantilever support while also focusing the laser beam and collecting the deflected light. The proposed cantilever design is expected to be useful in biology, physical sciences and engineering. The scan head should also be of general utility, and by being compact, is expected to improve background noise performance in any setting.
