Accessing
`Inaccessible
`Interfaces: In Situ
`Approaches to
`Materials Tribology
`
`W. Gregory Sawyer and Kathryn J. Wahl,
`Guest Editors
`
`Abstract
`The field of materials tribology has entered a phase of instrumentation and
`measurement that involves accessing and following the detailed chemical, structural,
`and physical interactions that govern friction and wear. Fundamental tribological
`research involves the development of new experimental methods capable of monitoring
`phenomena that occur within the life of a sliding contact. Measuring friction phenomena
`while the process is ongoing is a major improvement over earlier techniques that
`required the surfaces to be separated and analyzed, thereby interrupting the friction-
`causing event and modifying surface conditions. In the past, MRS Bulletinhas
`highlighted how insituapproaches can greatly enhance our understanding of materials
`structure, processing, and performance. This issue highlights insituapproaches as
`applied to materials tribology, namely, the study of contacting surfaces and interfaces in
`relative motion.
`
`Introduction
`Tribology is a field of study that is
`focused on the fundamental investigations
`of friction and wear. As recently summa-
`rized in a report on the “Frontiers of
`Fundamental Tribology,”1 new tools are
`needed to monitor tribological phenom-
`ena that are occurring within buried
` interfaces. These tools are essential for fun-
`damental studies of friction and wear
`because they are not intrinsic properties of
`a material; rather, they are functions of the
`tribological system (which includes the
`contacting surfaces that are in relative
`motion, the local environment, the back-
`ground temperature, the surface rough-
`ness and preparation, the sliding speeds
`and loads, and a host of other contribu-
`tors). Over the past half century, tribologi-
`cal systems have been discussed and
`described in terms of three basic groups of
`thematically linked elements:2 (1) the types
`
`of materials in contact and the contact
`geometry; (2) the operating conditions,
`including the gross motion, loads, stresses,
`and duration of operation; and (3) the
`environment and surface conditions,
`including the surface chemistry, surface
`topography, and ambient temperature.
`The incredibly large number of factors
`affecting tribological performance makes
`fundamental studies of materials tribology
`exceedingly difficult.
`Energy and material losses in moving
`mechanical devices as a result of friction
`and wear impose an enormous cost on the
`national economy. Engineering tribology
`involves the designs of bearings, bush-
`ings, and a wide variety of interfaces that
`support our everyday mobility and often
`aims to simultaneously reduce both fric-
`tion and wear. Practical solutions to miti-
`gate friction and wear have traditionally
`
`been through the use of fluid lubricants
`such as oils and greases. However, there
`are a number of applications where tradi-
`tional fluid lubrication strategies are either
`precluded or undesirable.3,4 Materials tri-
`bology, and in particular solid lubrication,
`is an area of research that aims to control
`friction and wear through both the appro-
`priate selection of known materials and
`the development of new materials and
`surface treatments.
`The contact between macroscopic sur-
`faces occurs on asperities, which are irreg-
`ularly shaped protuberances that exist on
`all engineering surfaces.5 Like fractals,
`these surface features occur across all
`length scales and define the distribution
`and shape of the real area of contact,
`which is orders of magnitude smaller than
`the apparent contact area.6–8 Thus, friction
`and wear arise from microscopic contacts
`that are under tremendous stresses and
`might have contact lifetimes of microsec-
`onds. In macroscopic systems, these con-
`tact locations are unknown and are buried
`in an apparent area of contact that is typi-
`cally inaccessible by most measurement
`techniques.
`Most materials tribology studies have
`focused on the friction coefficient and the
`wear rate. As shown in Figure 1, the fric-
`tion coefficient (µ) can be defined as the
`ratio of the friction force (Ff) to the normal
`force (Fn). The wear rate (K) is typically
`defined as the ratio of the volume of
` material removed (V) to the product of
`the applied normal load (Fn) and the dis-
`tance of sliding (d). Both the friction coef-
`ficient and the wear rate are sensitive to
`the starting conditions, load, speed, tem-
`perature, and environment. The initial
`transients during the approach to steady-
`state sliding are usually monitored but not
`modeled, and many of the reported and
`tabulated values for friction coefficients
`and wear rates are for steady-state
` conditions.
`To date, despite considerable efforts at
`understanding the origins of friction,
`there is no model capable of predicting
`friction coefficients from first principles.
`Similarly, there is no model for wear
`(which is often defined as the gradual
`removal of material from contacting sur-
`faces in relative motion) that is based on
`first-principles arguments. Thus, careful
`and proven experimental techniques rep-
`resent the most sophisticated and reliable
`approach for investigating, designing, and
`assessing the tribological worthiness of
`new materials. Fundamental studies of
`friction involve developing an under-
`standing of the real area of contact, surface
`chemistry, adhesion, and shear strength
`of the interface, as well as the nature of
`
`MRS BULLETIN (cid:127) VOLUME 33 (cid:127) DECEMBER 2008 (cid:127) www.mrs.org/bulletin
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`

`Accessing Inaccessible Interfaces: In SituApproaches to Materials Tribology
`
`Macroscopic Tribology
`Testing
`
`Fn
`
`Ff
`
`pin-on-disk
`configuration
`
`friction coefficient
`(ratio of friction force to normal force)
`µ = Ff/Fn
`
`wear rate
`(volume lost per unit normal load per distance of sliding)
`
`K =
`
`V
`Fn d
`
`(
`
`mm3
`N m
`
`)
`
`Fn
`
`real area of
`contact
`
`Ff
`
`flat-on-flat configuration
`
`locally high pressures
`within the real area of contact
`
`plowing and plastic
`deformation
`
`debris
`generation
`
`fn
`
`ff
`
`hard asperity or probe tip
`
`counterface material
`
`Wear and Friction at the Nanoscale
`
`Figure 1. Tribology measurements for friction coefficient (µ) are traditionally made dynamically through force transducers that record both
`the lateral, or friction force (Ff) and the normal force (Fn). Whether a spherically tipped pin or a flat countersurface, the real area of contact
`(shown in blue) is a very small component of the apparent or projected contact area. The wear rate (K), defined as a ratio of the volume of
`material removed (V) to the product of the normal load (Fn) and the sliding distance (d), is rarely measured under dynamic conditions.
`As shown in the inset (lower right), the contact pressures at the asperity level (ƒf and ƒn, where Ff = ∑ƒf and Fn = ∑ƒn) are typically large
`and approach the flow stress of the softer material. Single-asperity tribology measurements of friction can be accessed using atomic force
`microscope probes, and the deformation and structural transformation at this scale can be studied using tools such as insitutransmission
`electron microscopy.
`
`deformation and energy dissipation
`occurring at the asperity junctions.
`
`State of the Art
`There are no standard reference samples
`(such as the standard kilogram prototype
`maintained by the International Bureau of
`Weights and Measures) in materials tribol-
`ogy because the specimens are consumed
`during testing. Thus, friction and the pro-
`gression of wear must be monitored by
`sensitive force and displacement measure-
`ments and with periodic interruptions to
`examine the contacting surfaces. As illus-
`trated in Figure 2, two common in situ
`approaches are used to follow and link
`chemical, structural, and physical interac-
`tions with friction and wear processes.
`
`The most common in situ tribology
`approach has been to perform detailed
`measurements on the surface of the sam-
`ple within the environment but outside
`the contact. The tribofilms and surface
`topography that develop during testing
`can be carefully studied between contacts;
`postprocessing of the data enables cycle-
`by-cycle analysis that can be used to link
`data from the current cycle with the fric-
`tion and wear measurements of the previ-
`ous cycle. The advantage here is that the
`testing of the samples can take place
`under the appropriate tribological system
`conditions in an environment that is not
`varying during observation and experi-
`mentation. Full-scale engineering compo-
`nents down to devices on the scale of
`
`microelectromechanical systems can be
`analyzed in this way. A serious limitation
`is that the analytical measurements are
`not carried out within the contact, so infer-
`ences need to be drawn between the
`observations outside the contact and
`the probable dynamics (chemical and
`mechanical) that exist within the contact.
`In situ approaches that enable meas -
`urements within a contact are ideal.
`However, such approaches frequently
`require compromises of sample composi-
`tion, geometry, and testing environment
`to be made. For example, transparent
`materials enable observations of the inti-
`mate contact areas but are often not the
`traditional counterface material for the
`application. Additionally, spherical or pla-
`
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`

`Accessing Inaccessible Interfaces: In SituApproaches to Materials Tribology
`
`in situ approaches
`within the contact
`
`Fn
`
`Ff
`
`pin/counterbody
`
`real area of
`contact
`
`in situ approaches
`within the environment
`
`specified
`environment
`
`tribofilm
`
`wear track
`and debris
`
`solid lubricant
`coatings or bulk
`materials
`
`Figure 2. Various insituapproaches have been employed in tribological studies.
`Fundamental measurements of the real area of contact, the interfacial film or tribofilm
`chemistry, and the wear track morphology and wear rates are common goals. Here,
`microscope objectives illustrate pathways for insitustudies. The most common approach is
`to examine the surfaces emerging from a contact within the specified environment. A more
`complex scenario is to perform the measurements within the contact, as illustrated by the
`objectives looking through a transparent counterbody from above, below, or the side. Some
`compromise of the sliding contact (for example, materials, geometry, or scale) is typically
`required to achieve an insitumeasurement of this type.
`
`nar geometries are frequently selected for
`their suitability to the measurement rather
`than to the application. A number of ana-
`lytical techniques have been employed for
`in situ tribology studies. Many of these
`techniques are listed in Table 1, with
`examples of the measurement application,
`resolution, and limitations.
`The miniaturization of force and dis-
`placement measurement technologies
`have enabled a new suite of tribological
`test equipment that can be relatively easily
`integrated within a variety of existing
` surface analytical instruments. In other
`cases, advances in surface-science instru-
`mentation have enabled these tools to
`be integrated with existing tribological
`equipment. Together, the merging of
` surface analytical instrumentation and
`careful tribological instrumentation is pro-
`viding new and exciting opportunities to
`study the fundamentals of friction and
`wear.
`
`In This Issue
`In this issue of MRS Bulletin, we high-
`light the possibilities of applying in situ
`methods to the study of buried sliding
`interfaces found in tribological contacts.
`We have selected topics describing the
`state of the art in five areas ranging from
`the propagation of interfacial slip along
`crack fronts that simulate geological inter-
`faces relevant to earthquakes to nanoscale
`single-asperity contacts probing how
`small collections of atoms accommodate,
`and are transformed by, sliding. Whereas
`previous MRS Bulletin issues tackling
`materials tribology9–11 have highlighted a
`combination of parallel experimental and
`computational methods, the focus of this
`issue is on the development of experimen-
`tal approaches allowing direct probing of
`materials mechanics and chemistry active
`in sliding contacts. Two of the articles
`address fundamental studies of liquid and
`solid lubrication using a range of in situ
`
`microscopy and spectroscopy approaches.
`The article by Cann reviews the applica-
`tion of infrared and Raman microscopy to
` liquid-lubricated contacts, showing how
`the relationship between molecular con-
`formation, pressure, additives, and lubri-
`cant degradation can be correlated to
`friction performance. The article by Wahl
`and Sawyer reviews in situ approaches
`to understanding
`solid
`lubrication
` phenomena. Examples are provided to
`illustrate how optical and interference
`microscopy, Raman microscopy, and elec-
`tron microscopy are applied to link real-
`time changes in interfacial film chemistry,
`morphology, and rheology to friction and
`wear events.
`The remaining three articles address the
`state of the art in examining tribological
`contacts controlled by asperity-scale inter-
`actions. Marks et al. describe advances in
`in situ transmission electron microscopy to
`understand asperity–asperity interactions.
`The tools for controlling indentation
`and sliding of nanoscale contacts within
`the field of view of an electron microprobe
`provide unprecedented opportunities to
`observe atomic-scale tribological deforma-
`tion processes in real time. The article by
`Bennewitz and Dickinson reviews another
`aspect of the state of the art in in situ
`atomic-scale measurements of wear. In this
`case, carefully prepared surfaces and
` controlled chemical environments allow
`examination of the role of defects and
`chemistry in the initiation of wear and its
`relation to atomic-scale friction. The last
`article, by Rubenstein et al., describes
`in situ optical measurements of the onset of
`sliding that show that the crack front
`motion comprises velocities from sluggish
`(tens of meters per second) to beyond the
`shear wave speed (>1,000 m/s). These
`direct observations indicate how the onset
`of sliding is influenced and controlled by
`these unusual crack propagation modes.
`These articles illustrate a subset of the
`wide range of possibilities for applying
`in situ experimental methods to the chal-
`lenge of understanding the materials and
`interface science of buried sliding inter-
`faces. The in situ approaches could confirm
`or refute commonly accepted lubrication
`models and will allow closer comparison
`with molecular simulations of friction
`processes. Progress in materials tribology
`will depend on developing a detailed
`understanding of what is happening in
`buried sliding interfaces.
`
`Acknowledgments
`W.G.S. and K.J.W. gratefully acknowl-
`edge the support of the Office of Naval
`Research and the Air Force Office of
`Scientific Research.
`
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`

`

`Accessing Inaccessible Interfaces: In SituApproaches to Materials Tribology
`
`Table I: In situapproaches used for tribological interface studies
`
`Technique
`
`Measurement
`
`Optical microscopy
`
`Tribofilm formation and motion, contact size
`
`Interferometry (contact)
`
`Contact separation
`
`Interferometry (wear track) Wear
`
`Raman microscopy
`
`Composition/chemistry, film thickness
`
`ATR-FTIR spectroscopy
`
`Chemical bonding
`
`TEM + EELS + AFM/
`nanoindentation
`
`Microstructural transformation, interfacial film
`formation composition, chemistry
`
`SEM/EDX
`
`Surface morphology, composition
`
`Cross section of sliding surfaces w/o separation
`
`Structure
`
`Spatial
`Resolution
`~ 1 µm
`~ 1 µm
`~ 1 µm
`
`Limitations
`
`One counterface must be optically transparent.
`
`One counterface must be optically transparent.
`
`Index of refraction or reflectivity changes can
`distort results.
`
`One counterface must be optically transparent.
`
`~ 1 µm
`mm to cm One counterface must be IR-transparent.
`(width of
`crystal)
`
`0.1 nm
`
`10 nm
`
`0.1 nm
`µm’s
`
`Interface region must be electron-transparent;
`vacuum environment
`
`Contact charging, contamination in low
`vacuum environments
`
`Potential beam damage from FIB sectioning
`
`Requires synchrotron access
`
`SEM + FIB
`SFA + x-ray diffraction
`or neutron relativity
`
`AFM
`
`AES
`
`XPS
`
`Friction, surface topography, contact stiffness, wear
`
`~ 1 nm
`
`Difficult to ascertain contact size, chemistry
`
`Composition
`
`Composition, chemical state
`
`10 nm
`10s of µm
`
`Cannot probe inside contact zone
`
`Cannot probe inside contact zone
`
`Contact resistance
`
`Coating thickness, damage, interfacial film formation
`
`Note:ATR-FTIR, attenuated total reflection Fourier transform infrared spectroscopy; TEM, transmission electron microscopy; AFM, atomic force microscopy; EELS,
`electron energy loss spectroscopy; SEM, scanning electron microscopy; EDX, energy dispersive x-ray spectroscopy; FIB, focused ion beam; SFA, surface force
`apparatus; AES, Auger electron spectroscopy; XPS, x-ray photoelectron spectroscopy.
`
`References
`1. S.S. Perry, W.T. Tysoe, Tribol. Lett. 19 (3), 151
`(2005).
`2. F.P. Bowden, D. Tabor, Br. J. Appl. Phys. 17
`(12), 1521 (1966).
`3. P.J. Heaney, A.V. Sumant, C.D. Torres, R.W.
`Carpick, F.E. Pfefferkorn, Diamond Relat. Mater.
`17 (3), 223 (2008).
`
`4. M.R. Hilton, P.D. Fleischauer, Surf. Coat.
`Technol. 55 (1–3), 435 (1992).
`5. J.A. Greenwood, J.B. P. Williams, Proc. R. Soc.
`London A 295 (1442), 300 (1966).
`6. B.N.J. Persson, Phys. Rev. Lett. 8711 (11),
`116101 (2001).
`7. B.Q. Luan, M.O. Robbins, Nature 435 (7044),
`929 (2005).
`
`8. C. Campana, M.H. Muser, M.O. Robbins,
`J. Phys.: Condens. Matter 20 (35) (2008).
`9. “Materials Tribology,” MRS Bull. 16 (10),
`(1991).
`10. “Nanotribology,” MRS Bull. 18 (5), (1993).
`11. “Fundamentals of Friction,” MRS Bull. 23
`■■
`(6), (1998).
`
`Mechanical and
`Aerospace Engineering,
`Gainesville, FL 32611,
`USA; and e-mail
`wgsawyer@ufl.edu.
`Sawyer is the N.C.
`Ebaugh Professor of
`Mechanical and
`Aerospace Engineering
`at the University of
`Florida. He received his
`PhD degree from
`Rensselaer Polytechnic
`Institute in 1999.
`Sawyer’s research
` interest is in the area of
`materials tribology. Over
`the past decade, the
`
`Tribology Laboratory at
`the University of Florida
`has developed numerous
`experimental appara-
`tuses for interrogating
`materials under extreme
`environments, including
`vacuum, cryogenic, and
`high temperature. The
`laboratory also designed
`and built an array of tri-
`bometers that are cur-
`rently scheduled to be
`operated in space as
`part of a 2009
`NASA–Materials
`International Space
`Station Experiment.
`
`Sawyer also has been
`active in developing
`polymeric nanocompos-
`ites for solid lubrication
`(recently demonstrating
`ultra-low wear with
`polytetrafluoroethylene
`nanocomposites) and
`probing the molecular
`origins of friction and
`wear (using a coupled
`computational simula-
`tion and experimental
`tribology program at the
`University of Florida).
`Additionally, Sawyer
`was chair of the 2008
`International Joint
`
`W. Gregory Sawyer
`
`Kathryn J. Wahl
`
`W. Gregory Sawyer,
`Guest Editor for this
`issue of MRS Bulletin,
`
`can be reached at the
`University of Florida,
`Department of
`
`1148
`
`MRS BULLETIN (cid:127) VOLUME 33 (cid:127) DECEMBER 2008 (cid:127) www.mrs.org/bulletin
`
`Regeneron Exhibit 1166.004
`Regeneron v. Novartis
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`

`

`Accessing Inaccessible Interfaces: In SituApproaches to Materials Tribology
`
`Roland Bennewitz
`
`Gil Cohen
`
`J. Thomas Dickinson
`
`Jay Fineberg
`
`Laurence D. Marks
`
`Tribology Conference
`and serves on the edito-
`rial boards of the jour-
`nals Wear and Tribology
`Letters.
`
`Kathryn J. Wahl, Guest
`Editor for this issue of
`MRS Bulletin, can be
`reached at U.S. Naval
`Research Laboratory,
`Code 6176, Washington
`DC 20375, USA; tel.
`1-202-767-5419; and
`e-mail kathryn.wahl@nrl.
`navy.mil.
`Wahl heads the
`Molecular Interfaces and
`Tribology Section at the
`Naval Research
`Laboratory (NRL). She
`joined the NRL in 1992 as
`a National Research
`Council Postdoctoral fel-
`low and became a staff
`scientist in 1995. She
`received a B.A. in
`Physics and Mathematics
`from St. Olaf College in
`1987, and a Ph.D. in
`Materials Science and
`Engineering from
`Northwestern University
`in 1992. Her research has
`focused on fundamental
`physics and chemistry of
`sliding and adhesive
`interfaces, both at macro-
`scopic and nanometer
`scales. Currently, her
`research efforts include
`the development of
`in situ chemical and
`mechanical methods to
`probe bioadhesive con-
`tacts created by marine
`biofoulants, such as bar-
`nacles. Wahl chaired the
`2008 Tribology Gordon
`
`Research Conference,
`serves on the editorial
`boards of Tribology Letters
`and Wear, and is a fellow
`of the American Vacuum
`Society.
`
`Roland Bennewitz can
`be reached at INM—
`Leibniz Institute for New
`Materials, Campus D2 2,
`66123 Saarbrücken,
`Germany; and e-mail
`roland.bennewitz@inm-
`gmbh.de.
`Bennewitz is head of
`the Nanotribology Group
`at the INM—Leibniz
`Institute for New
`Materials in Saarbrücken,
`Germany. He received
`his Habilitation degree
`from the University of
`Basel, Switzerland, in
`2002. Bennewitz was an
`assistant professor at
`McGill University in
`Montreal, Canada, from
`2004 until 2008, where he
`also held the Canada
`Research Chair in
`Experimental
`Nanomechanics. His
`main research focuses are
`the microscopic mecha-
`nisms of friction and
`wear and the mechanical
`properties of materials
`with a nanometer-scale
`structure.
`
`Philippa M. Cann can be
`reached by e-mail at
`p.cann@imperial.ac.uk.
`Cann is a principal
`research fellow in the
`Tribology Group at
`Imperial College
`London. Throughout the
`
`last 20 years, her research
`has focused on experi-
`mental studies of lubrica-
`tion and lubricants,
`particularly grease lubri-
`cation of rolling element
`bearings. More recently,
`Cann has been develop-
`ing experimental meth-
`ods in biotribology and,
`in particular, synovial
`joint lubrication research.
`Her research has been
`recognized by a number
`of awards: the IMecE
`Thomas Stephen Prize
`(1996), the STLE Walter
`D. Hodson Award (1998),
`the STLE Wilbur Deutsch
`Award (2001), the NLGI
`Authors Award (2000),
`and the Royal Swedish
`Academy of Engineering
`Sciences, Jacob
`Wallenberg Foundation
`Grant (2004). In 2004,
`Cann was awarded the
`Institution of Mechanical
`Engineers, Tribology
`Silver Medal from the
`Tribology Trust.
`
`Gil Cohen can be
`reached at the Racah
`Institute of Physics,
`Hebrew University of
`Jerusalem, Givat Ram,
`Jerusalem 91904, Israel;
`tel. 972-2-6585720; fax
`972-2-6584437; and
`e-mail gilc@vms.huji.ac.il.
`Cohen has been a labo-
`ratory researcher at the
`Hebrew University of
`Jerusalem since 2003. He
`received his PhD degree
`from the Hebrew
`University of Jerusalem
`in 2000. His research
`
`interests include friction,
`fracture, nonlinear phe-
`nomena, and biophysics.
`
`J. Thomas Dickinson
`can be reached at
`Washington State
`University, Pullman, WA
`99164-2814, USA; tel.
`509-335-4914; and
`e-mail jtd@wsu.edu.
`Dickinson is the Paul
`A. Anderson Professor
`of Physics and Regents
`Professor at Washington
`State University (WSU).
`He also leads the Surface
`Dynamics Group at
`WSU. Dickinson
`received his bachelor’s
`degree from Western
`Michigan University
`and his PhD degree in
`physics at the University
`of Michigan. He joined
`the faculty at WSU in
`1968. Dickinson’s work
`has focused on the
`interaction and conse-
`quences of mechanical,
`chemical, and radiative
`stimuli on primarily
`nonmetallic materials.
`His current research
`interests include
`nanometer scale
`tribochemistry and
`VUV/femtosecond laser-
`surface interactions. He
`is the author/co-author
`of more than 320 refereed
`publications and is a
`fellow of MRS, APS, AVS,
`and AAAS.
`
`Jay Fineberg can be
`reached at the Racah
`Institute of Physics,
`Hebrew University of
`
`Jerusalem, Givat Ram,
`Jerusalem 91904, Israel;
`tel. 972-2-6585207; fax
`972-2-6584437; and
`e-mail jay@vms.huji.ac.il.
`Fineberg has been a
`faculty member at the
`Hebrew University of
`Jerusalem since 1992 and
`holds the Max Born
`Chair in Natural
`Philosophy. He received
`his PhD degree from the
`Weizmann Institute of
`Science in 1988. His inter-
`ests include fracture, the
`dynamics of friction,
`nonlinear wave interac-
`tions, and nonlinear phe-
`nomena. The recipient of
`a number of prestigious
`awards, Fineberg also
`has authored numerous
`scientific papers.
`
`Laurence D. Marks can
`be reached at the
`Department of Materials
`Science and Engineering,
`Northwestern University,
`Evanston, IL 60208, USA;
`tel. 847-491-3996; and
`e-mail L-marks@
`northwestern.edu.
`Marks is a professor of
`materials science and
`engineering at
`Northwestern University.
`After receiving his BA
`degree in chemistry at
`the University of
`Cambridge, UK, and his
`PhD degree in physics at
`the Cavendish
`Laboratory, Cambridge,
`UK, Marks was a post-
`doctoral researcher at
`Cambridge and at
`Arizona State University.
`
`MRS BULLETIN (cid:127) VOLUME 33 (cid:127) DECEMBER 2008 (cid:127) www.mrs.org/bulletin
`
`1149
`
`Regeneron Exhibit 1166.005
`Regeneron v. Novartis
`IPR2021-00816
`
`

`

`Accessing Inaccessible Interfaces: In SituApproaches to Materials Tribology
`
`Arno Merkle
`
`Andrew Minor
`
`Shmuel M. Rubinstein
`
`Oden L. Warren
`
`He joined the faculty of
`Northwestern University
`in 1985. Marks’ current
`research interests include
`nanotribology,
`dry-cutting, transmission
`electron microscopy,
`oxide surface science and
`catalysis, nanoparticles,
`solid-oxide fuel cells,
`nanoplasmonics, and
`density- functional theory.
`In addition, he is the
`author or co-author of
`more than 250 refereed
`articles.
`
`Arno Merkle can be
`reached at Carl Zeiss
`SMT Inc., One
`Corporation Way,
`Peabody, MA 01960,
`USA; tel. 617-515-5031;
`and e-mail
`a.merkle@smt.zeiss.com.
`Merkle is a transmis-
`sion electron microscopy
`(TEM) specialist at Carl
`Zeiss SMT Inc. for their
`operations in North
`America. In 2001, he
`received a BA degree in
`physics at Gustavus
`
`Adolphus College in St.
`Peter, MN. Merkle
`earned his PhD degree in
`2007 from the Materials
`Science and Engineering
`Department at
`Northwestern University.
`His research experience
`and collaborations
`extend to a number of
`institutions worldwide,
`including Argonne
`National Laboratory
`(USA), the Max Planck
`Institute for Metals
`Research in Stuttgart,
`Germany, and the
`Fraunhofer Institute for
`the Mechanics of
`Materials in Freiburg,
`Germany. Merkle’s
`research interests com-
`bine both theoretical
`(physical model genera-
`tion) and experimental
`(in situ TEM) approaches
`to understanding funda-
`mental nanoscale mecha-
`nisms at tribological
`interfaces. He is the
`recipient of a DAAD
`research grant and was
`named teaching
`
`assistant of the year
`while at Northwestern
`University.
`
`Andrew Minor can be
`reached at 1 Cyclotron
`Road, MS 72, Berkeley,
`CA 94720, USA; tel. 510-
`495-2749; fax 510-486-
`5888; and e-mail
`aminor@berkeley.edu.
`Minor is an assistant
`professor of materials
`science and engineering
`at the University of
`California, Berkeley
`(UCB), and also a
`faculty scientist at the
`National Center for
`Electron Microscopy
`at the Lawrence
`Berkeley National
`Laboratory. He
`received his bachelor’s
`degree in economics
`and mechanical engi-
`neering from Yale
`University and
`his MS and PhD degrees
`in materials science
`and engineering from
`UCB. Minor’s research
`group focuses on
`
`nanomechanical
`size effects, characteriza-
`tion of soft materials,
`and novel in situ TEM
`methods for materials
`science research.
`
`Shmuel M. Rubinstein
`can be reached at the
`Racah Institute of
`Physics, Hebrew
`University of Jerusalem,
`Givat Ram, Jerusalem
`91904, Israel; tel. 972-2-
`6584330; fax 972-2-
`6584437; and e-mail
`rshmuel@vms.huji.ac.il.
`Rubinstein is nearing
`completion of his PhD
`degree studies at the
`Racah Institute of
`Physics of the Hebrew
`University of Jerusalem.
`He received his BS
`and MS degrees from
`the Hebrew University
`of Jerusalem. The
` recipient of the Charles
`Clore fellowship in
`2007, Rubinstein’s
`interests include the
`dynamics of friction,
`fracture, and nonequilib-
`
`rium electro-osmotic
`instabilities.
`
`Oden L. Warren can be
`reached by e-mail at
`owarren@hysitron.com.
`Warren is the chief
`technology officer of
`Hysitron, Inc. He received
`his PhD degree in physi-
`cal chemistry from Iowa
`State University, where he
`performed ultrahigh-
`vacuum surface science
`research on ultrathin-
`film systems. Thereafter,
`Warren advanced the
`interfacial force micro-
`scope as a postdoctoral
`fellow at Sandia National
`Laboratories, New
`Mexico, and the
`University of Western
`Ontario, Canada. He
`joined Hysitron in 1998,
`where he has led a
`number of major instru-
`mentation development
`projects related to
`nanomechanical
`testing—including
`serving as the principal
`investigator of several
`U.S. Department of
`Energy Small Business
`Innovation Research
`grants. Warren has
`co-authored more than
`50 papers in surface
`science, nanomechanics,
`and nanotribology
`fields and has received
`an R&D 100 Award
`for the development
`of a quantitative
`nanoindenter for the
`transmission electron
`microscope.
`
`■■
`
`1150
`
`MRS BULLETIN (cid:127) VOLUME 33 (cid:127) DECEMBER 2008 (cid:127) www.mrs.org/bulletin
`
`Regeneron Exhibit 1166.006
`Regeneron v. Novartis
`IPR2021-00816
`
`