One-Dimensional Constrained Blister Test to Measure Thin Film Adhesion

Schematic of a pressurized 1D rectangular film adhering to a rigid constraining plate above

Mechanical response of (a) contact length, c, (b) contact angle, θ, and (c) force to keep plate in equilibrium, F, as functions of applied pressure for w₀ = 1 and fixed adhesion energy. Initial loading along OA causes the film to bulge but yet to touch the plate. For γ = 5, pressurization along AB causes (a) contact to expand from null to maximum, (b) θ to remain at zero, and (c) F to increase to counterbalance the rising pressure. Initial depressurization along BCD causes (a) c to remain constant, (b) θ to increase to raise G, and (c) F to diminish. Further decrease in p causes delamination along DP, where (a) contact shrinks, (b) θ to rise further, and (c) F to diminish further. Pinch-off occurs at P when the contact area reduces to a line and the film spontaneously detaches from the plate. Stronger adhesion with γ = 20 retraces the loading path OAB. Initial depressurization along BCDHK where the contact remains unchanged. Further decrease in p leads to delamination along KQ. Pull-off occurs at Q when dp/dc = 0.

Changing film profile for w₀ = 1. (a) Initial pressurization along OAB causes the film to bulge and the contact to expand. (b) For γ = 5, pressure decreases along BCDP. Along BCD, the contact area remains unchanged but θ increases. Delamination occurs along DP until pinch-off at P. (c) For γ = 20, pressure decreases along BCDHKQ with pull-off at Q. The curves are labeled based on Fig. 2.

Contact length as a function of applied pressure for w₀ = 1 and a range of adhesion energy. The lowest curve corresponds to γ = 0, and the area underneath is forbidden. Curves labeled γ = 5 and γ = 20 correspond to those shown in Figs. 2 and 3. Curve labeled γ^† = 8 indicates the transition from pinch-off to pull-off. The locus of pull-off (dp/dc = 0) is shown as gray curve.

Relations of “pull-off” parameters for a range of w₀. (a) Critical pressure and (b) contact length as functions of adhesion energy with a range of gap w₀. (c) Critical contact length as a function of critical pressure. The symbols denote the transition γ = γ^† from pinch-off to pull-off.