Atomic force microscopy, a tactile-based probe technique, provides a three-dimensional nanoscale image of a material by gliding a needle-like arm across the material's surface. The core of AFM imaging workhorse is a cantilever with a sharp tip that deflects as it encounters undulations across a surface. Due to a minimum force required for imaging, conventional AFM cantilevers can deform or even tear apart living cells and other biological materials. While scientists have made strides in reducing this minimum force by making smaller cantilevers, the force is still too great to image cells with high resolution. Indeed, for imaging objects smaller than the diffraction limit of lightthat is, nanometer dimensionsthis approach hits a roadblock as the instrument can no longer sense minute forces.
Now, however, scientists with the Molecular Foundry, a U.S. Department of Energy User Facility located at Berkeley Lab, have developed nano-sized cantilevers whose gentle touch could help discern the workings of living cells and other soft materials in their natural, liquid environment. Used in combination with a revolutionary detection mechanism, this new imaging tool is sensitive enough to investigate soft materials without the limitations present in other cantilevers.
"Whether we are considering biological systems or other complex, self-assembling nanostructures, this organization will be done in a liquid," says Paul Ashby, a Molecular Foundry staff scientist who led this research in the Foundry's Imaging and Manipulation of Nanostructures Facility. "If we have an investigative probe that excels in this environment, we could image individual proteins as they function on the cell surface."
Says Babak Sanii, a post-doctoral researcher in the Foundry, "Shrinking the cantilever down to nanoscale dimensions dramatically reduces the force it applies, but to monitor the movements of such a small cantilever, we needed a new detection scheme."
|Contact: Aditi Risbud|
DOE/Lawrence Berkeley National Laboratory