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

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

Biological materials: Structure and mechanical properties

Discrete particle simulation of particulate systems: Theoretical developments

Mussels attach to solid surfaces in the sea. Their adhesion must be rapid, strong, and tough, or else they will be dislodged and dashed to pieces by the next incoming wave. Given the dearth of synthetic adhesives for wet polar surfaces, much effort has been directed to characterizing and mimicking essential features of the adhesive chemistry practiced by mussels. Studies of these organisms have uncovered important adaptive strategies that help to circumvent the high dielectric and solvation properties of water that typically frustrate adhesion. In a chemical vein, the adhesive proteins of mussels are heavily decorated with Dopa, a catecholic functionality. Various synthetic polymers have been functionalized with catechols to provide diverse adhesive, sealant, coating, and anchoring properties, particularly for critical biomedical applications.

Mussel-Inspired Adhesives and Coatings

Contact angle measurement and contact angle interpretation

This paper discusses the influence of surface energy on the contact between elastic solids. Equations are derived for its effect upon the contact size and the force of adhesion between two lightly loaded spherical solid surfaces. The theory is supported by experiments carried out on the contact of rubber and gelatine spheres.

Surface energy and the contact of elastic solids

A novel rolling-contact experiment has been devised with the object of making direct observations of viscoelastic behaviour of elastohydrodynamic lubricant films. A 'point contact' disk machine has been used which permits the axes of the disks to be either tilted or skewed through small angles relative to each other. Tilt subjects the film to cyclic shear while skew subjects it to unidirectional shear. By measuring and comparing the resultant shear forces developed by the film in each case, its viscoelastic properties can be deduced. Experiments at 23 degrees C with a high-viscosity mineral oil revealed viscoelastic behaviour above a contact pressure of about 0.5 GPa. In the pressure range 1.0 to 2.0 GPa the effective elastic shear modulus of the oil was found to vary from 0.1 to 1.0 GPa. At a pressure of 0.8 GPa the oil exhibited a viscoelastic transition in the temperature range 70 to 30 degrees C. The investigation was restricted to small shear strains for which the behaviour is linear.

A. D. Roberts

Papers

Surface energy and the contact of elastic solids

Observations of Viscoelastic Behaviour of an Elastohydrodynamic Lubricant Film