Introduction to Compact Discs

• Compact discs have many different uses such as music and data storage

• The information stored on the disc is done so in small pits stamped into the polycarbonate layer

There are several layers to a compact disc Graphic layer – above data layer Lacquer layer – above data layer Reflective layer – above data layer Polycarbonate layer – data layer is on top

Data Layer of Compact Disc magnified 3000x

 

Successful vs. Unsuccessful

Wood glue magnified 3000x

Elmer’s glue magnified 2370x

Tacky glue magnified 3000x

Matthew Javener, Dr. John KirkDepartment of Chemistry, University of Wisconsin-Stout

Compact Discs: Music, Data, Lithography?

Introduction to Soft Lithography

• Soft lithography is a low cost method for the formation of nanostructures

• The process involves stamping nano- or micro-structures into a polymer to form a pattern

Soft lithography process

Start with master Pour on elastomer

Remove polymer Allow to polymerize

Uses for soft lithography

Biotechnology – this process gives people the ability to pattern complex molecules that are associated with biology

Electronics – this process allows people to reproduce very small features on electronics quickly and with little cost

 

Step 1 – Removing Protective Layers

• Duct tape was pressed firmly against the top layers and then peeled off

Outer layers removed using duct tape

• This process was done several times to obtain the clearest surface possible

Polymer Advantages and DisadvantagesBackground• This experiment was designed to determine whether or not simple adhesives could be used in combination with a compact disc as a soft lithography method

• Soft lithography is an expensive process which leads to many young students never learning how it is done

• The nature of this process makes it unique and useful in many aspects of life such as:

Biotechnology, Electronics, Optics, and Biochemistry

 

Polymer Cost Advantages Disadvantages

Wood Glue $1.67• Fast curing (1 hr. approx.)• Easily removable• Low Cost

• Degrades at high magnification with SEM

White Glue $0.97• Easily removable• Low Cost• Low viscosity

• Degrades at high magnification with SEM• Slow curing (3 hr. approx.)

Tacky Glue $1.97• Low Cost• Fast curing (30 min approx.)

• High viscosity

• Wood glue is a possible polymer to use for lithography

• This image shows that the wood glue forms the reverse image of the disc

• White glue is a possible polymer to use for lithography

• This image shows that the white glue forms the reverse image of the disc

• Tacky glue was an unsuccessful polymer to use for lithography

• This image shows no sign of the data layer from the disc due to the high viscosity of the polymer

Conclusion• Soft lithography can be done using a compact disc and readily available polymers

• With a more viscous polymer the chance is greater that the lithography will work

• Care should be taken when imaging these types of polymers to avoid damaging the structure

• The process done throughout this experiment would be an excellent way to teach young students about lithography

Step 2 – Applying Different Polymers

• Common adhesives (polymers) were applied to the exposed surface of the disc

Elmer’s Glue Wood Glue Tacky Glue

• Each polymer was allowed to cure overnight

• After the polymers were cured they were removed from the surface

• Care was taken to avoid scratching the features on the polymer

Step 3 – Examining Products

• The disc was coated with a thin layer of gold and examined under a scanning electron microscope

• The polymers that were peeled off were coated with gold and examined under the microscope

• The polymers had to be examined at slow scan speeds and lower magnification to avoid destruction of the surface

• Once images were taken they were compared to determine whether or not the polymer produced a reverse image of the disc

Polyvinyl Acetate (PVA)

Vinyl acetate monomer Polyvinyl acetate polymer

• PVA is the polymer that is present in each of the three glues that were used in this experiment

• Although these glues are each made of the same polymer they act differently because of the formation of cross-links

• Cross-links form when one polymer chain is connected to another chain

Cross-linking between two polymer chains

• Cross-links can form at different rates depending on what other chemicals are present in the glue

• The more cross-linking that is present the more dense the material will become

Acknowledgments I would like to extend a special thanks to the follow people for their help on this experiment

Dr. Ray for his help on experimental design Jack Stransky for his help teaching me how to use the SEM