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Biomaterials

Biomaterials - Poster Session E

O29 - Investigating Phase Separation Behavior and Substrate Influence in Rapid Prototyping of Porous Membranes for Cell Culture Applications

Saturday, October 11, 2025
10:00 AM - 11:00 AM PDT
Location: Exhibit Hall F, G & H

    Presenting Author(s)

  • CS

    Caleb Sefranek

    Undergraduate Research Assistant
    Rochester Institute of Technology
    Pittsford, New York, United States

    • Primary Investigator(s)

  • CS

    Caleb Sefranek

    Undergraduate Research Assistant
    Rochester Institute of Technology
    Pittsford, New York, United States

    • Co-Author(s)

  • Leanna H. Frasch

    Research Assistant
    Rochester Institute of Technology
    Rochester, New York, United States

    • Last Author(s)

  • Thomas Gaborski

    Professor and Department Head
    Rochester Institute of Technology
    Rochester, New York, United States


Introduction: : With the rise of research related to tissue on a chip technology for mimicking physiological conditions and the effect of substrate interactions on extracellular vesicle (EV) production for cell types such as Mesenchymal stem cells (MSCs) - having consistent cost-effective methods to tune the properties of commonly used deformable substrates such as Polydimethylsiloxane (PDMS) is valuable for advancing understanding of cellular processes and enhancing cell culture methodologies. As such, this project aims to build off the existing work of Yap 2024, in using spin-casting-assisted polymer-blend phase separation to create thin, flexible, and highly porous membrane for cell culture applications, by exploring the importance of substrate choice, mixture ratios, and polystyrene (PS) on phase separation properties. Additionally this project wishes to introduce a new substrate, thin film (~76um) Polyethylene Terephthalate (PET) which was found to improve the handling of the thin PDMS layer and achieve comparable pore sizes and distributions. The results of this project could potentially be used to develop curved or walled devices, or a disrupted surface bed that may provide insights into the topographical cues involved in cell signaling pathways and their effects of extracellular vesicle release for MSCs.

Materials and

Methods: : 6 inch silicon wafers are diced into 3.5 by 3.5 cm square pieces within a biosafety cabinet (BSC). Thin laminated PET film is attached to the silicon wafer via orange double sided polyimide tape. To form a sacrificial layer, 4% or 10% weight by volume polyvinyl alcohol (PVA) is spin coated at 4000 rpm for 30s on silicon wafer pieces without PET. The sacrificial layer is allowed 24 hours to dry. Next, 10:1, base to crosslinker, PDMS (Slygard 184) is added to a glass bottle with a varied ratio mixture of 40,000 or 800-5000 molecular weight atactic flake PS and 99.5% toluene. Ratios of 1 or 2 parts toluene to 1 part PDMS and 0.10 or 0.13 parts PS were tested with PVA layers and PET. A small magnetic stir bar is added to the bottle and used to mix the solution for 30 minutes at 2150 rpm. After this time the PS pellets should be dissolved leading to a cloudy homogenous solution that will be spin coated onto each layered wafer. The wafer is secured and then spun and allowed to ramp up to a speed of 6000 rpm over 8 seconds before the prepared solution is deposited centrally. After deposition the wafer continuously spins for another 60 seconds at 7000 rpm. Wafers are baked for 24 hours at 80℃ and then etched in 99.5% toluene for 20 minutes. Lastly, residual toluene is evaporated with an overnight bake at 80℃.

Results, Conclusions, and Discussions:: From figures 1a and 1b, the final pores formed on PET films from a ratio of 1 part toluene to 1 part PDMS and 0.10 parts PS, resulted in the reduction of larger pores (>15 μm) when compared to the same blend on silicon substrates suggesting base substrate influences phase-separation behavior for a toluene, PDMS, and PS mixture. There was a slight increase in the number of larger pores (>15 μm) observed on top of the PET film when PS ratio increased from 0.10 to 0.13 hinting at the sensitivity of the PET layer to changes in the blend ratio. Additionally from figures 1a and 1b, a 4% PVA sacrificial layer appears to have a masking effect resulting in similar pore size contributions to the porosity across both the underlying silicon wafer substrate and the PET film. As the PET film resulted in favorable PS distribution, resulting in pore sizes no larger than 16μms was observed when spin coating 1:1:0.1 (Toluene:PDMS:PS) mixtures onto PET films has potential for cell culture experiments with immortalized mesenchymal stem cells (iMSCs) and observing the effects of surface topography on extracellular vesicle release.

Acknowledgements and/or References (Optional): : The primary inspiration for this work came from the work done by Kimura lab based in Tokyo University.

Jin Hong Yap, Hong Zhang, Yosuke Okamura, Hiroshi Kimura,
Thin microporous polydimethylsiloxane membrane prepared by phase separation and its applications for cell culture,
Materialia, Volume 38, 2024, 102247, ISSN 2589-1529, https://doi.org/10.1016/j.mtla.2024.102247.
(https://www.sciencedirect.com/science/article/pii/S2589152924002448)