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 Hongbo Zeng Zeng

• Dr. Jacob
• Dr. Jacob Israelachvili

Israelachvili 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

Preparation of polymer thin films

Measure surface and interfacial energy Measure the adhesion and the friction of polymer films Conclusion (relate the experiment results 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

Block polymer with low surface energy

Water

Block polymer with high surface energy

100 0 0 45 0

Surface Force Apparatus (SFA) Surface Force Apparatus (SFA)

Approximately 3.5 Approximately 3.5” ”x5 x5” ”x4 x4” ”. . 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 and interfacial energy. and interfacial energy.

4’’ 5’’ 3.5’’

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

Our Results: Symmetric Case Our Results: Symmetric Case

S-T instabilities ri ro

Growth of the contact region Growth of the contact region

0.1 1 10 100 1000 10000 10 100 0.1 1 10 100 1000 10000 100 120 140 160 180 Contact diameter, 2ro, 2ri (µm) Contact time, t (s) PS 800

1st exponential decay, R

2=0.99608

2nd exponential decay, R

2=0.99941

Minimum gap distance, D (nm)

Black dots- gap distance Blue- outer contact radius Blue white- inner contact radius

i

• (

) / 2 ,

n

r r r t = + ∝

1 2

/ / 1 2 3 t t

D C e C e C

τ τ − −

+ + ฀

where C1, C2, C3 are constants, and τ 1 << τ 2 where n =0.2-0.3

=

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 Thin film, related to cell-

• cell coalescence

cell coalescence (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-

• liquid coalescence.

liquid coalescence. Effects of viscosity on adhesion and Effects of viscosity on adhesion and detachment. detachment. Finger instabilities with adhesive contacts Finger instabilities with adhesive contacts

• f materials from liquid
• f materials from liquid-
• like to solid

like to solid-

• like.

like. Contact angle measurements and its Contact angle measurements and its relation to surface energy. relation to surface energy.

Acknowledgements Acknowledgements

Hongbo Hongbo Zeng Zeng

• Dr. Jacob
• Dr. Jacob Israelachvili

Israelachvili Interfacial Laboratory Interfacial Laboratory CNSI CNSI INSET INSET