Hot Embossing of Thermoplastic Elastomers in Fabrication of Microfluidic Cell Culture Devices
Hossain, Emon (2025)
2025
Bioteknologian ja biolääketieteen tekniikan maisteriohjelma - Master's Programme in Biotechnology and Biomedical Engineering
Lääketieteen ja terveysteknologian tiedekunta - Faculty of Medicine and Health Technology
Hyväksymispäivämäärä
2025-12-01
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-2025120111086
https://urn.fi/URN:NBN:fi:tuni-2025120111086
Tiivistelmä
In recent years, there has been growing interest in exploring elastomer materials beyond polydimethylsiloxane (PDMS) for microfluidic and organ-on-chip devices, as PDMS presents well-known limitations in scalability and chemical compatibility. Soft thermoplastic elastomers (sTPE) are a promising option because they combine the elasticity and transparency of PDMS with the production scalability of thermoplastics [3].
In this work, we present a fabrication method for TPE-based microfluidic devices using hot embossing with epoxy molds. We describe a fabrication route comprising (i) casting a PDMS intermediate mold from an SU-8 master, (ii) producing a durable epoxy mold from the PDMS replica, and (iii) plate-to-plate hot embossing of soft TPE sheets to achieve rapid, repeatable replication of microscale features. We thoroughly investigated resin-to-hardener formulations to maximize epoxy mold lifetime and optimized embossing pressure and temperature to replicate the original microstructures. We evaluated the replicated microfluidic chips by profilometry for height analysis, optical inspection for defect rates and quality of microstructure replications.
We assessed surface hydrophilicity after oxygen plasma treatment and polyvinylpyrrolidone (PVP) coating and compared the results against similar PDMS chips. We found that for TPE chips, the first emboss reproduced the design within a few percent, with feature widths 11.0–12.8 µm and lane-to-lane variation of 0.4–0.9 µm. Widths increased from 11.0–12.8 µm initially to 11.8–12.9 µm at cycle 5 with variation of 0.5–1.1 µm and 12.8–14.7 µm with variation of 0.6–2.2 µm at cycle 10. The epoxy mold showed no visible damage until 10 runs. Mold feature height averaged 138.7 ± 2.9 µm relative to a 126 µm SU-8 reference (+10.1% on average).
In this work, we present a fabrication method for TPE-based microfluidic devices using hot embossing with epoxy molds. We describe a fabrication route comprising (i) casting a PDMS intermediate mold from an SU-8 master, (ii) producing a durable epoxy mold from the PDMS replica, and (iii) plate-to-plate hot embossing of soft TPE sheets to achieve rapid, repeatable replication of microscale features. We thoroughly investigated resin-to-hardener formulations to maximize epoxy mold lifetime and optimized embossing pressure and temperature to replicate the original microstructures. We evaluated the replicated microfluidic chips by profilometry for height analysis, optical inspection for defect rates and quality of microstructure replications.
We assessed surface hydrophilicity after oxygen plasma treatment and polyvinylpyrrolidone (PVP) coating and compared the results against similar PDMS chips. We found that for TPE chips, the first emboss reproduced the design within a few percent, with feature widths 11.0–12.8 µm and lane-to-lane variation of 0.4–0.9 µm. Widths increased from 11.0–12.8 µm initially to 11.8–12.9 µm at cycle 5 with variation of 0.5–1.1 µm and 12.8–14.7 µm with variation of 0.6–2.2 µm at cycle 10. The epoxy mold showed no visible damage until 10 runs. Mold feature height averaged 138.7 ± 2.9 µm relative to a 126 µm SU-8 reference (+10.1% on average).