Title: High-Throughput Adhesion Testing of Combinatorial Libraries with Multi-lens Arrays

Authors: Aaron M. Forster, Wen-Hua Zhang, Christopher M. Stafford

The NIST Combinatorial Methods Center (NCMC) has adapted the Johnson, Kendall, and Roberts (JKR) test to develop a high-throughput adhesion measurement platform. Traditionally, the JKR test utilizes a single hemispherical lens compressed against (loading) and removed from (unloading) a substrate. After the test, the JKR theory is used to model the contact behavior between two elastic solids to quantify the adhesive forces as a function of contact area, contact geometry, and load or displacement. The high-throughput adaptation of this test utilizes an array of hemispherical lenses, rather than a single lens, to conduct multiple adhesion tests during one loading/unloading cycle. Essential to the quantification of adhesion energies with the JKR equation is the measurement of two of three variables: load, contact area, and displacement. Typically, the contact area and load are measured during the test and this data is fit to the JKR equation to determine E and G, the system modulus and energy release rate, respectively. Experimentally, displacement is not used due to difficulties in determining the initial contact point for a single lens test. The application of multiple lenses should yield a better estimation of the initial contact point, thus allowing a more precise determination of the energy release rate.

In this presentation, multi-lens adhesion tests will be compared to single lens tests to determine the potential for utilizing displacement of the multi-lens array as an experimental variable to quantify strain energy. Also, we discuss the use of single lens experiments, in conjunction with infrared and fluorescence measurements, to investigate epoxy curing along a temperature gradient. The main focus of this discussion will be the ability and applicability of contact adhesion measurements to characterize the extent of epoxy curing and the comparison of adhesion measurements to both infrared and fluorescence measurements.

Division: Polymers Division

Laboratory: Materials Science and Engineering Laboratory

Room and Building address: B224 and building 224

Mail Stop: 8542

Telephone: 975-4877

Fax: 975-4924

Email: aaron.forster@nist.gov

Sigma Xi member: No

Relevant Category: Materials and Engineering