The objective of this Phase I SBIR project is to demonstrate fully the feasibility of nano-thin, high strength, polyimide membrane as a significantly improved sample support for Transmission Electron Microscopy (TEM). TEM samples are currently supported on metal mesh grids and on fragile membranes of thinned formvar and other fragile materials.
Our aim i s to produce a fundamentally new tool for TEM, viz., unobstructed TEM sample substrates with millimeter-scale sample apertures and with no intervening grid bars -a tool that may be highly useful for TEM scientists and technicians. Preliminary tests with 1.5mm diameter open aperture films have shown that 40-70nm thick membranes of high strength polyimide have very desirable TEM properties. These include high electron beam transmission, excellent dimensional stability during beam illumination, absence of image artifacts or background texture, low X-ray background emission, and minimal sample stain uptake. The robust character of this new sample support approach was most apparent during the sample preparation process. These early prototypes have been used in the same manor as conventional metal grids to pickup TEM samples from aqueous surface films. These initial experiments were done without film failure and without unusual care. In another demonstration of robustness, a number of these membrane grids were shipped by car and plane without special protection and without damage. None of these results could be reliably expected from a similar Formvar sample geometry. The proposed research collaboration is an investigation of the full range of application enhancements that this new sample support technology can contribute to TEM science. We will also develop the manufacturing techniques needed to produce high quality, affordable membrane gridless sample holders in commercial quantities. The specific product will be a new class of robust TEM sample supports with large (2mm) unobstructed apertures and ease of use similar to conventional metal grids. The high reliability of these sample supports will be a particular benefit where loss of irreplaceable or high-value samples must be avoided. ? ?
