Adhesion and Detachment Adhesion and Detachment Mechanisms of - PowerPoint PPT Presentation

Adhesion and Detachment Adhesion and Detachment Mechanisms of Polymer Surfaces Mechanisms of Polymer Surfaces Victor Murillo Victor Murillo Biochemistry Major Biochemistry Major Ventura College Ventura College Hongbo Zeng Zeng Hongbo Dr. Jacob Israelachvili Israelachvili Dr. Jacob NSF, DOE, NASA NSF, DOE, NASA

Big Picture Big Picture This project primarily focuses on adhesion and separation of This project primarily focuses on adhesion and separation of polymers polymers Patterns associated with these processes. Patterns associated with these processes. There is a broad range of applications from this research. There is a broad range of applications from this research.

Processes Processes Measure surface and interfacial Preparation of polymer thin films energy Conclusion Measure the adhesion and the (relate the experiment results friction of polymer films to theory)

Spin Coating Spin Coating

Surface and interfacial energy Surface and interfacial energy Set up used for contact Set up used for contact angle measurements and angle measurements and radius spread. radius spread. Drop is recorded using a Drop is recorded using a digital camera. digital camera. With contact angle, we With contact angle, we can calculate the surface can calculate the surface energy of the polymer. energy of the polymer. We can also plot the data We can also plot the data to get graphs which can to get graphs which can help us see the growth help us see the growth rate of the radius and the rate of the radius and the decrease rate of the decrease rate of the contact angle. contact angle.

High surface energy vs. low High surface energy vs. low surface energy surface energy Water Water 45 0 100 0 0 Block polymer with Block polymer with high surface energy low surface energy

Surface Force Apparatus (SFA) Surface Force Apparatus (SFA) Approximately 3.5” ”x5 x5” ”x4 x4” ”. . Approximately 3.5 Price of box itself is Price of box itself is $200,000. $200,000. Designed by Dr. Jacob Designed by Dr. Jacob Israelachvili. Israelachvili . Measure the thickness, Measure the thickness, adhesion and friction adhesion and friction forces, contact distance, forces, contact distance, and pull off velocity of and pull off velocity of polymer films. polymer films. We can also relate this We can also relate this information with surface information with surface 4’’ and interfacial energy. and interfacial energy. 3.5’’ 5’’

Fringes of Equal Chromatic Order Fringes of Equal Chromatic Order (FECO) (FECO)

Our Results: Symmetric Case Our Results: Symmetric Case S-T instabilities r o r i

Growth of the contact region Growth of the contact region 0.1 1 10 100 1000 10000 180 Black dots- gap 160 Minimum gap distance, D (nm) Contact diameter, 2r o , 2r i ( µ m ) distance PS 800 Blue- outer contact 140 100 radius Blue white- inner 120 contact radius 2 =0.99608 1st exponential decay, R 100 2 =0.99941 2nd exponential decay, R 10 0.1 1 10 100 1000 10000 Contact time, t (s) = − τ − τ + + t / t / D C e C e C ฀ 1 2 = + ∝ n 1 2 3 r ( r r ) / 2 , t i o where C1, C2, C3 are constants, where n =0.2-0.3 and τ 1 << τ 2

Future Plans Future Plans Our research is mostly fundamental which Our research is mostly fundamental which practices theoretical methods. practices theoretical methods. Adhesion and detachment mechanisms can Adhesion and detachment mechanisms can contribute to many fields. contribute to many fields. Make better adhesive polymers. Make better adhesive polymers. Propose better theories for detachment Propose better theories for detachment mechanisms. mechanisms. Have a better understanding of adhesion Have a better understanding of adhesion mechanisms and theories. mechanisms and theories. Thin film, related to cell- -cell coalescence cell coalescence Thin film, related to cell (potential application). (potential application).

What did I learn in this research? What did I learn in this research? Surface energy. Surface energy. Adhesion of polymers, thin films Adhesion of polymers, thin films Liquid- -liquid coalescence. liquid coalescence. Liquid Effects of viscosity on adhesion and Effects of viscosity on adhesion and detachment. detachment. Finger instabilities with adhesive contacts Finger instabilities with adhesive contacts of materials from liquid- -like to solid like to solid- -like. like. of materials from liquid Contact angle measurements and its Contact angle measurements and its relation to surface energy. relation to surface energy.

Acknowledgements Acknowledgements Hongbo Zeng Zeng Hongbo Dr. Jacob Israelachvili Israelachvili Dr. Jacob Interfacial Laboratory Interfacial Laboratory CNSI CNSI INSET INSET