# Presentation: 477907

## Physico-Chemical Characterization and Processing of Nanocomposite Polymers for Microfluidic Applications

- Surface hydrophobicity can be controlled via remote plasma of spun-cast thin films of polylymethylmethacrylate-45% polyhedral oligomeric silsesquioxane (PMMA-POSS) from highly hydrophobic to highly hydrophilic depending on exposure conditions.
- Work is ongoing to understand the surface chemistry change affected by plasma exposure.
- Prior results with contact angles and ToF-SIMS data suggested that the surface becomes enriched with SiOx and that the plasma degrades the isobutyl groups surrounding the POSS cages.
- Current work involves XPS and spectroscopic ellipsometry (SE) data.
- Film thickness as-deposited is ~ 130Å
- SE shows that the film etches up to ~22Å after plasma exposure and then appears to stop etching suggesting that the SiOx layer passivates the surface (Figure 1).
- A calculation of the thickness of 45 wt% PMMA-POSS film required to be removed to fully cover the surface is ~25Å.
- Ongoing work is to repeat this experiment with 10 wt% PMMA-POSS film to determine if this saturates at a greater thickness change.
- XPS data shows a decrease in C percentage with a corresponding increase in O and Si percentage (Figure 2).
- Ongoing high resolution XPS is being performed to understand changes in surface chemistry of the plasma treated films.

- Brian H. Augustine, Wm. Christopher Hughes, James Madison University **DMR-0405345**
**RECENT ACTIVITIES**

- A novel method to rapidly prototype polymeric mcrostructures has been developed that we have called “Micromolding using Polymerization in Capillaries (-PIC)”. The fabrication procedure follows and is depicted below in Figure 3:
- A silicon master is produced via conventional microlithography techniques.
- PMMA beads can be used as spacers to control the thickness of the -PIC layers.
- A prepolymerized solution of PMMA / MMA with a photoinitiator is flowed between a PMMA baseplate and the Si master via capillary force.
- The structure is photopolymerized under UV irradiation.
- Advantages of this technique include:
- Ability to rapidly prototype polymeric microstructures
- Excellent fidelity in pattern transfer from the master
- Ability to produce microstructures made from novel materials that can be either photopolymerized or thermally initiated
- Fabrication of multi-layered structures
- Fabrication of buried layered structures

**FIGURE 1:** Thickness change of PMMA-45%-POSS thin film after 95% N2 / 5% O2 remote plasma exposure as determined by SE.

**FIGURE  3:** Schematic of -PIC micromolding process.

**Plasma Surface Modification of POSS-Based Polymers**

**Micromolding Using Polymerization **
**in Capillaries (********-PIC)**

**FIGURE 2:** Atomic % of Si, O and C as measured by XPS of plasma-treated POSS-based thin films

## Physico-Chemical Characterization and Processing of Nanocomposite Polymers for Microfluidic Applications

- Eight undergraduate students were directly funded through this project from the Departments of Physics and Chemistry at James Madison University this past year. For the summer 2006 term, rising senior, **Jacob Forstater** (Physics), is working on development of -PIC PCR devices and rising sophomore, **John Wyrick **(Physics), is working on a rapid prototype scheme for polymer microfluidic fabrication. Summer 2005, six students were funded through this grant. These were **Forstater** and rising seniors, **Katy Zimmermann** and **Patrick Turner** (Chemistry) who worked on plasma surface modification of POSS based polymers and characterization and soft lithographic patterning of polymers, respectively. May 2006 graduate **Melissa Lane** and May 2005 graduate **Rozine Lindamood **(both Chemistry) worked on microfabrication of polymeric structures.
- A middle school science teacher, **Karen Bland** (May 2003 graduate in physics) worked for eight weeks on a project of microfabrication of demonstration devices for middle and high school science teachers.
- Three women funded through this project this past year are enrolled or will be enrolling in graduate school:
- Ms. **Toni Bonhivert** is enrolled in a PhD in chemistry at Georgia Tech studying biomaterials / materials chemistry
- Ms. **Rebekah Esmaili** is enrolling in a PhD program in Materials Science and Engineering at North Carolina State University
- Ms. **Karen Bland** is enrolling in a MS program in astrophysics at Baylor University.
- Forstater, Zimmerman, Turner and Wyrick plan on attending graduate school in SMET disciplines after graduation
- Jacob Forstater has worked half of the summer 2006 in the Augustine / Hughes lab at JMU and is currently spending six weeks working in the lab of Dr. James Landers at the University of Virginia. He is working on comparison of device performance of polymeric -PIC PCR chips with glass PCR devices fabricated by the Lander’s group.

- Brian H. Augustine, Wm. Christopher Hughes, James Madison University **DMR-0405345**
**Undergraduate Mentoring and R1 Collaboration**

**Katy Zimmerman ***(JMU Chemistry)*** **describing spectroscopic ellipsometry to CAA university provosts at Colonial Academic Alliance conference Research After Hours.

**Jacob Forstater ***(JMU Physics)*** **presenting research at Colonial Academic Alliance poster session April 2006.

**STUDENT PRESENTATIONS**
- _K. Zimmerman_, W. C. Hughes, B. H. Augustine, “Synthesis and Characterization of Polymer Brushes”, Colonial Academic Alliance Conference, James Madison University, Harrisonburg, VA  April  2006
- _J. Forstater_, W. C. Hughes, B. H. Augustine, “A Novel Technique for Fabricating Microfluidic Devices by Photopolymerization”, Colonial Academic Alliance Conference, James Madison University, Harrisonburg, VA  April 2006
- _R. Esmaili_, J. Forstater, B. H. Augustine, W. C. Hughes, “Modification of Nanocomposite POSS-PMMA Surfaces by Exposure to Reactive Oxygen”, American Physical Society March Meeting Baltimore, MD 2006
- _P.L. Turner_, B.H. Augustine, “*In-situ* Monitoring of Polymer Biodegradation Using Atomic Force Microscopy”, 30th National American Chemical Society Meeting, Washington, DC August, 2005
- _K. Zimmerman_, W.C. Hughes, B.H. Augustine, “Characterization of Polymer Brushes”, 30th National American Chemical Society Meeting, Washington, DC August, 2005