title: Active mixing of complex fluids at the microscale.
abstract: Mixing of complex fluids at low Reynolds number is fundamental for a broad range of applications, including materials assembly, microfluidics, and biomedical devices. Of these materials, yield stress fluids (and gels) pose the most significant challenges, especially when they must be mixed in low volumes over short timescales. New scaling relationships between mixer dimensions and operating conditions are derived and experimentally verified to create a framework for designing active microfluidic mixers that can efficiently homogenize a wide range of complex fluids. Active mixing printheads are then designed and implemented for multimaterial 3D printing of viscoelastic inks with programmable control of local composition.
authors.affiliation: School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Ober
authors.affiliation: School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138.
authors.forename: Daniele
authors.initials: D
authors.lastname: Foresti
authors.affiliation: School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138 jalewis@seas.harvard.edu.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Lewis
keywords: 3D printing; graded materials; microfluidic mixing; yield stress fluids