# Presentation: 279550

## 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 polyhedral oligomeric silsesquioxane-co-polylymethylmethacrylate (POSS-MA) from highly hydrophobic to highly hydrophilic depending on exposure conditions and POSS concentration (See Figure 1).
- Current analysis work involves XPS, ToF-SIMS, contact angle, atomic force microscopy and spectroscopic ellipsometry (SE) data.
- Film thickness as-deposited is ~ 180Å
- SE shows that the film etches after plasma exposure, but the etch rate decreases with increasing POSS percentage. This suggests that a SiOx layer passivates the surface (Figure 2).
- XPS data shows a decrease in C percentage with a corresponding increase in O, Si and Ta percentage (Figure 3).
- High resolution XPS data confirms model of SiOx surface enrichment in plasma-treated films.
- AFM data suggests that 2000 s plasma treatment results in significant surface damage. AFM also reveals in interesting surface morphology for the 45 wt. % POSS-MA that suggests phase separation of the materials that is currently under study.

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

- A novel method to rapidly prototype polymeric microstructures has been developed that we have called “Micromolding using Polymerization in Capillaries (-PIC)”. This work is currently being written up for submission to *Lab on a Chip*.
- 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:** Change in contact angle of POSS-MA thin films with varying POSS composition after 95% N2 / 5% O2 remote plasma exposure.

**FIGURE  4:** SEM of -PIC PCR well with buried Au mirror.

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

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

**FIGURE 3:** Atomic % of 45 wt% POSS-MA films for Si, O, C and Ta as measured by XPS of plasma-treated POSS-based thin films with varying exposure time.

**FIGURE 2:** Thickness change of POSS-MA thin films after 95% N2 / 5% O2 remote plasma exposure as determined by SE.

- B.H. Augustine, W.C. Hughes, K.J. Zimmermann, A.J. Figuerido, X. Guo, C.C. Chusuei, J.S. Maidment, *Langmuir*, **23**, 4346-4350 (2007)

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

- Six undergraduate students were directly funded through this project this past year. For the summer 2006 term, recently graduated senior, **Jacob Forstater** (JMU Physics), worked on development of -PIC PCR devices and rising junior, **John Wyrick **(JMU Physics), worked on a rapid prototype scheme for polymer microfluidic fabrication. Summer 2007, four students were funded through this grant. These were rising seniors, **Patrick Turner** (JMU Chemistry) and **Ashley Figuerido (**Sweet Briar College Biochemistry), rising sophomore **Matthew Bradley** (JMU Chemistry) and recently graduated senior senior, **Katy Zimmermann** (JMU Chemistry). Figuerido and Zimmermann worked on plasma surface modification of POSS based polymers. Bradley worked on silane surface modification strategies of plasma-treated POSS surfaces, and Turner worked on -PIC development.
- Five students who have directly worked on this project are enrolled or will be enrolling in graduate school:
- Ms. **Katy Zimmermann** is enrolled in a MS program in environmental science at the University of California-Riverside
- Mr. **Jacob Forstater** is enrolled in a PhD program in Physics and Astronomy at the University of North Carolina-Chapel Hill
- Figuerido, and Wyrick plan on attending graduate school in SMET disciplines after graduation. Turner is planning on an MD/PhD program after graduation.
- Students worked with Dr. Lindsay Legendre in the laboratory of Dr. James Landers at the University of Virginia in the Department of Chemistry on the design and fabrication of polymeric PCR microchips with imbedded Au mirrors for IR mediated PCR.
- Three undergraduate student authors on recent *Langmuir* paper: Zimmermann (JMU), Figuerido (Sweet Briar College), and Maidment (Randolph Macon Women’s College)

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

**Ashley Figuerido ***(Sweet Briar College Biochemistry)*** **preparing a POSS-MA sample for plasma treatment in the cleanroom at JMU.

**Patrick Turner ***(JMU Chemistry, foreground)*** **looking at -PIC device using an optical microscope and** Matthew Bradley ***(JMU Chemistry, background)*** **literature searching.

**STUDENT PRESENTATIONS**
- _A. J. Figueiredo_*, B. H. Augustine, W. C. Hughes, K. J. Zimmermann*, C. C. Chusuei, “Plasma Surface Modification of POSS-MA Films on Ta-Coated Si Wafers”, 233rd National American Chemical Society Meeting, Chicago, IL CHED 804 (3/26/07) (Chem Ed: Polymer Chemistry)
- _K. J. Zimmermann_*, B. H. Augustine, W. C. Hughes, A. J. Figuerido*, “Surface Modification and Characterization of POSS-Based Acrylic Thin Films”, 233rd National American Chemical Society Meeting, Chicago, IL COLL 287 (3/26/07) (Fundamental Research in Colloid and Surface Chemistry)
- _B. H. Augustine_, W. C. Hughes, K. J. Zimmermann*, A. J. Figuerido*, X. Guo, C. C. Chusuei, “Surface Characterization of Oxygen Plasma Treated POSS-Based Acrylic Polymer Thin Films”, 233rd National American Chemical Society Meeting, Chicago, IL POLY-549 (3/26/07) (Sci-Mix)