Leang Recieves Molecular Vista/DOE Grant
February 17, 2015
Mechanical engineering associate professor Kam Leang and industry collaborator Molecular Vista, Inc. received a nine-month Department of Energy (DOE) grant for $150,000. The project is entitled, “Video-Rate Atomic Force Microscope for Functional Gas and Liquid Environments”.
Molecular Vista, Inc. (MVI) in collaboration with the University of Utah and others will develop a high speed (~ 10 frames/second) atomic force microscope (HS AFM) for real-time in-situ characterization of electrochemical, photoelectrochemical, and fuel cell reactions. HS AFM and associated scanning probe techniques will provide insights into various fundamental questions and applied challenges in surface dynamics at the nanoscale. The goal is to develop a user-friendly, high resolution and ultrafast AFM for functional gas and liquid environment to support basic science in energy research as specified in topic 7b. The proposed instrument is expected to have roughly a thousand-fold increase in throughput compared to typical commercially available systems with comparable scan range and resolution.
High speed (> 2 frames/second) and high resolution (molecular resolution) AFM imaging of biomoleculesin liquid environment has yielded progress in fundamental understanding in the protein and nucleotide dynamics. Similarly HS PFM (Piezo Force Microscopy) at 1 frame/second has led to direct observation of ferroelectric domain as it evolves. The only commercial instrument that is available currently for high speed imaging is not practical for wide-spread use due to limitations on scan range and sample size. Additionally, the ultra-small cantilever utilized in the tool cannot be adequately protected against the harsh and corrosive environment via additional coatings since the concomitant increase in the force constant will lower the sensitivity. Finally, the required beam bounce detection mechanism for the ultra-small cantilever makes the instrument difficult to operate.
The proposed new instrument will be based on quartz crystal sensor known as length extension
resonator (LER) operated in frequency modulation AFM (FM AFM) mode. In UHV, LER operated in FMAFM has demonstrated true atomic resolution. While Q (~ 400) of typical non-contact AFM cantilevers in air increases to about 35,000 in UHV, Q for LER sees only a modest increase from air (~ 20,000) to UHV (~ 50,000). Therefore, we anticipate only a modest reduction in Q for LER and sustained sensitivity for true atomic resolution even when fully immersed in liquid. Other benefits of using LER include (1) ease-of-use due to electrical excitation and sensing and (2) ability to concurrently bias the metallic tip during AFM operation to provide additional flexibility in electrochemistry research.
In Phase I, MVI will (1) develop an encapsulation for LER for passivation against corrosive liquid while maintaining high Q in liquid; (2) demonstrate imaging with high sensitivity in full liquid immersion; (3) prototype a high-bandwidth demodulation circuitry for high speed FM AFM; (4) prototype a high-speed sample scanner and a prototype HS LER AFM head; and (5) demonstrate the feasibility of high speed imaging in air using the prototypes. Item (3) will be headed by Tom Albrecht, our consultant who first demonstrated FM AFM while item (4) will be performed by Prof. Kam Leang’s laboratory in University of Utah; the rest will be carried out at MVI.