http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Graphene-polymer nanocomposites for structural and functional applications

Tribology of polymers: Adhesion, friction, wear, and mass-transfer

Electrical conductivity of compacts of graphene, multi-wall carbon nanotubes, carbon black, and graphite powder

Highly sensitive sensor arrays are in high demand for prospective applications in remote sensing and imaging. Measuring microscopic deflections of compliant micromembranes and cantilevers is developing into one of the most versatile approaches for thermal, acoustic and chemical sensing. Here, we report on an innovative fabrication of compliant nanocomposite membranes with nanoscale thickness showing extraordinary sensitivity and dynamic range, which makes them candidates for a new generation of membrane-based sensor arrays. These nanomembranes with a thickness of 25–70 nm, which can be freely suspended over large (hundred micrometres) openings are fabricated with molecular precision by time-efficient, spin-assisted layer-by-layer assembly. They are designed as multilayered molecular composites made of a combination of polymeric monolayers and a metal nanoparticle intralayer. We demonstrate that these nanocomposite membranes possess unparalleled sensitivity and a unique autorecovering ability. The membrane nanostructure that is responsible for these outstanding properties combines multilayered polymer/nanoparticle organization, high polymer-chain orientation, and a pre-stretched state.

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Freely suspended nanocomposite membranes as highly sensitive sensors

FUNDAMENTALS OF ELECTRICAL CONTACTS Introduction to Electrical Contacts . Introduction . Summary of Basic Features Contact Mechanics . Surface of Solids . Surface Topography . Modern Techniques of Measuring Surface Parameters . Contact of Smooth Surfaces . Contact between Rough Surfaces Tribology . Friction . Wear . Lubrication . Current Trends in Tribology Contact Materials . Metallic Contact Materials . Coatings for Electrical Contacts . Composite Contact Materials . Nanostructured Materials Current and Heat Transfer across the Contact Interface . Contact Resistance . Interfacial Heating Reliability Issues in Electrical Contacts . Significance of Electrical Contacts Reliability . Electrical Contact Requirements . Factors Affecting Reliability . Connection Degradation Mechanisms . Impact of Connection Degradation APPLICATIONS OF ELECTRICAL CONTACTS Power Connections . Types of Power Connectors . Design Features and Degradation Mechanisms . Mitigating Measures . Installation Procedures Electronic Connections . Types of Electronic Connections . Materials for Electronic Connections . Degradation Mechanisms in Electronic Connections . Mitigating Measures Sliding Contacts . Tribology of Electrical Contacts . Dry Metal Contacts . Lubricated Metal Contacts . Composite Contacts DIAGNOSTIC AND MONITORING TECHNOLOGIES Electrical Methods in Tribology . Surface Characterization . Diagnosis of Contact Area and Friction Regimes . Evaluation of Tribological Performance of Materials and Lubricants Monitoring Technologies . Thermal Measurements . Resistance Measurements . Monitoring Contact Load (Pressure) . Ultrasonic Measurements . Wireless Monitoring . Cost Benefits of Monitoring and Diagnostics Techniques Appendix 1: Methods of Description of Rough Surface Appendix 2: Shape-Memory Materials Appendix 3: Electrical Contact Tables References Index

Electrical Contacts: Fundamentals, Applications and Technology

Scanning force microscopy (SFM) was used for probing micromechanical properties of compliant polymeric materials. Classic models of elastic contacts, Sneddon's, Hertzian, and JKR, were tested for various indentation depths and for a variety of polymeric materials. We selected extremely compliant polyisoprene rubbers (Young's modulus, E = 1−3 MPa), elastic polyurethanes (E = 5−50 MPa), and hard surfaces of polystyrene (PS) and polyvinylchloride (PVC) (E = 1−5 GPa). Both Sneddon's and Hertzian elastic models gave consistent and reliable results in the range of indentation depths up to 200 nm which are close to JKR solution. Close correlation is observed between absolute values of elastic moduli determined by SFM and known values for bulk materials.

Micromechanical Properties of Elastic Polymeric Materials As Probed by Scanning Force Microscopy

The approach developed for the microindentation of layered elastic solids was adapted to analyze atomic force microscopy probing of ultrathin (1–100 nm-thick) polymer films on a solid substrate. The model for analyzing microindentation of layered solids was extended to construct two- and tri-step graded functions with the transition zones accounting for a variable gradient between layers. This “graded” approach offered a transparent consideration of the gradient of the mechanical properties between layers. Several examples of recent applications of this model to nanoscale polymer layers were presented. We considered polymer layers with elastic moduli ranging from 0.05 to 3000 MPa with different architecture in a dry state and in a solvated state. The most sophisticated case of a tri-layered polymer film with thickness of 20–50 nm was also successfully treated within this approach. In all cases, a complex shape of corresponding loading curves and elastic modulus depth profiles obtained from experimental data were fitted by the graded functions with nanomechanical parameters (elastic moduli and transition zone widths) close to independently determined microstructural parameters (thickness and composition of layers) of the layered materials.

/pdf/nanomechanical-probing-of-layered-nanoscale-polymer-films-1dzouqctl4.pdf

Nanomechanical probing of layered nanoscale polymer films with atomic force microscopy

Polymer tribology is a fast growing area owing to increasing applications of polymers and polymer composites in industry, transportation, and many other areas of economy. Surface forces are very important for polymer contact, but the real origin of such forces has not been fully investigated. Strong adhesive interaction between polymers leads to an increase in the friction force, and hence, the asperities of the material may be removed to form wear particles or transfer layers on the counterface. The theory of polymer adhesion has not been completely elucidated yet and several models of adhesion have been proposed from the physical or chemical standpoints. This paper is focused on the research efforts on polymer adhesion with emphasis on adhesion mechanisms, which are very important in the analysis of polymer friction and wear.

/pdf/adhesion-and-surface-forces-in-polymer-tribology-a-review-lss3qez6pv.pdf

Nikolai K. Myshkin

Papers

Tribology of polymers: Adhesion, friction, wear, and mass-transfer

Electrical Contacts: Fundamentals, Applications and Technology

Micromechanical Properties of Elastic Polymeric Materials As Probed by Scanning Force Microscopy

Nanomechanical probing of layered nanoscale polymer films with atomic force microscopy

Adhesion and surface forces in polymer tribology—A review