title: Introducing natural thermoplastic shellac to microfluidics: A green fabrication method for point-of-care devices.
abstract: We present a sustainable fabrication method for cheap point-of-care microfluidic systems, employing hot embossing of natural shellac as a key feature of an energy-efficient fabrication method that exclusively uses renewable materials as consumables. Shellac is a low-cost renewable biomaterial that features medium hydrophilicity (e.g., a water contact angle of ca. 73°) and a high chemical stability with respect to common solvents such as cyclohexane or toluene, rendering it an interesting candidate for low-cost microfluidics and a competitor to well-known systems such as paper-based or polydimethylsiloxane-based microfluidics. Moreover, its high replication accuracy for small features down to 30 μm lateral feature size and its ability to form smooth surfaces (surface roughness Ra  = 29 nm) at low embossing temperatures (glass transition temperature Tg  = 42.2 °C) enable energy-efficient hot embossing of microfluidic structures. Proof-of-concept for the implementation of shellac hot embossing as a green fabrication method for microfluidic systems is demonstrated through the successful fabrication of a microfluidic test setup and the assessment of its resource consumption.
authors.affiliation: Laboratory for Microactuators, Department of Microsystems Engineering - IMTEK, University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Lausecker
authors.affiliation: Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT) , Herman-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Badilita
authors.affiliation: Laboratory for Materials Processing, Department of Microsystems Engineering - IMTEK, University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: U
authors.identifier: 0000-0002-7999-7143
authors.initials: U
authors.lastname: Gleißner
authors.affiliation: Laboratory for Microactuators, Department of Microsystems Engineering - IMTEK, University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Wallrabe