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Tevis D. B. Jacobs, PhD
Associate Professor
538-E Benedum Hall | 3700 O’Hara Street | Pittsburgh, PA 15261 P: 412-624-9736
tjacobs@pitt.edu
Nanoscale Contact Phenomena
The focus of the Jacobs Research Group is to reveal the atomic-scale processes governing the mechanical and transport properties of surfaces and interfaces at the nanoscale. Contacting surfaces are of critical importance in advanced nanoscale applications, including micro-/nano-electromechanical systems, manufacturing schemes, and microscopy applications. The function of such applications depends on the ability to precisely predict and control contact parameters such as contact stiffness, contact area, adhesion, and electrical contact resistance. Our group uses novel combinations of scanning probe microscopy, electron microscopy, and mechanical testing techniques to interrogate the mechanical behavior of contacts between nanoscale bodies, and the interdependence between mechanical properties and functional properties of the contact.
Scanning probe techniques are used inside of a transmission electron microscope (TEM). By simultaneously achieving Angstrom-scale spatial resolution and nanonewton force resolution, we can interrogate individual nanoscale bodies – including the formation and separation of their contact, and its evolution under load. Using an in situ TEM nanomanipulator with specialty scanning probe microscopy tips, we can simultaneously measure transport properties – such as electrical contact resistance and heat transfer. This enables the quantitative interrogation of the load-dependence of functional properties, and the effects of surface properties, such as roughness or structure/ chemistry of surface layers.
Scaling up Insights from Nanocontacts to Describe Behavior of Micro- and Macro-scale Surfaces
Nano-/micro-mechanical testing is performed on rationally designed multi-point contacts – either few-asperity tips, or nominally flat surfaces with nanoscale roughness. Insights from single nanocontacts are used to describe larger-scale behavior. Our goal is to develop quantitative, fundamental, and predictive understanding of nanoscale contact behavior, which will enable tailored properties for advanced technologies across length scales.
Figures: Left, top: Scanning probe microscopy techniques are employed in the transmission electron microscope. Right: An example lattice-resolved image of a nanoscale contact during an in situ loading test. Left, bottom: A micro-mechanical tester is used on larger samples enabling connections across length scales.
