MRI: Acquisition of a Field Emission Cryo-Scanning Electron Microscope for Nanocharacterization and Patterning of Soft Materials

0922522

Libera

Stevens Institute of Technology

Technical Summary: This project applies a new, state-of-the-art, cryo-scanning electron microscope (SEM) to measure soft-materials morphology at high spatial resolution. This new microscope will advance over ten research projects at Stevens Institute of Technology and enable them to follow important directions that amplify their ongoing and anticipated aims. All involve soft materials ? either synthetic polymers, biological structures, or combinations of the two. Among the materials being studied are: self-assembled, weak-polyelectrolyte, responsive micelles; nanoparticle composites; degradable scaffolds that mimic natural bone; infection-resistant orthopedic implants; natural extracellular matrix; and synthetic nanofiber extracellular matrices. Synthetic and natural polymers are challenging materials to study by electron microscopy because of their radiation sensitivity, weak intrinsic contrast, and susceptibility to electrical charging. This new microscope provides controllable electron accelerating voltages enabled at low voltages by a field-emission (FEG) electron source; gas compensation to mitigate specimen charging; high-efficiency electron detectors that minimize the required incident dose; robust methods for digital image acquisition/processing; cryo-imaging capabilities for studying frozen-hydrated materials; and hardware/software for robust electron-beam lithography. All of these features are either inadequate or unavailable on the SEM the new microscope replaces. Importantly, the new SEM is housed in a central user facility with a history of successful multidisciplinary training that spans high school through post-graduate school. Users receive substantial training both by concentrated hands-on self-user practice and by graduate lecture/lab course work. In addition to serving the immediate Stevens research community, the instrument plays an important role in community outreach and education by way of collaborative activities with the Stevens Center for Innovative Engineering and Science Education, an established K-16 outreach organization, and the Project SEED program of the American Chemical Society.

Layman Summary: Scanning electron microscopes (SEMs) are used to study the surfaces of materials at magnifications between about 20 and 500,000 times. They can provide important information about the structure and composition of materials. So-called soft materials, such as plastics and biological tissue, are typically more challenging to study by electron microscopy than metals or semiconductors, because soft materials can become both electrically charged and chemically changed by the electrons used in the microscope. At Stevens Institute of Technology there are more than ten research projects, all of which involve soft materials, whose progress is limited by the need to do more and better SEM imaging and analysis. The newest scanning electron microscopes incorporate innovative features that can help Stevens researchers overcome the problems of specimen charging and chemical damage. To take advantage of these, this project is using a new, state-of-the-art, SEM to measure soft-materials morphology and help Stevens researchers make new discoveries. These scientists are, for example, using the microscope to develop new ways to delivery drugs, to make hip and knee implants more infection resistant, and to help heal major bone fractures. Because this new microscope is a complex instrument, it is housed in a laboratory with a dedicated staff and facilities to both maintain the microscope and provide the advanced training needed for university students to make the best use of this new tool. Importantly, however, many aspects of the microscope are relatively easy to use and understand, so this microscope is also helping Stevens develop connections to the surrounding community through a variety of high-school outreach programs designed to get more young people aware of and interested in science and engineering.