Paper Number
AM9 

Session
Additive Manufacturing and Composites

Title
Methods of microencapsulation of responsive microparticle suspensions

Presentation Date and Time
October 13, 2021 (Wednesday) 2:45

Track / Room
Track 3 / Meeting Room A-B

Authors (Click on name to view author profile)

  1. Wilson-Whitford, Samuel (Lehigh University, Department of Chemical and Biomolecular Engineering)
  2. Gao, Jinghui (Lehigh University, Department of Chemical and Biomolecular Engineering)
  3. Roffin, Maria C. (Lehigh University, Department of Chemical and Biomolecular Engineering)
  4. Kaewpetch, Thitiporn (Lehigh University, Polymer Science and Engineering)
  5. Gilchrist, James F. (Lehigh University, Department of Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Samuel Wilson-Whitford1, Jinghui Gao1, Maria C. Roffin1, Thitiporn Kaewpetch2 and James F. Gilchrist1
1Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015; 2Polymer Science and Engineering, Lehigh University, Bethlehem, PA 18015

Speaker / Presenter 
Wilson-Whitford, Samuel

Keywords
active materials; colloids; composites; gels; non-Newtonian fluids; suspensions

Text of Abstract
Particle containing composite microcapsules have become increasingly prevalent and are widely employed for applications including pharmaceutical, personal care, nanocomposite self-healing barrier films and coatings industries. Most commonly, small particles are held at the interface or physically arrested in a solid core. Microencapsulation through polymerization at the interface of emulsion droplets has been successful in creating capsules of fluids that can be then incorporated in other media. However, due to surface energy and Pickering stabilization, it is difficult to encapsulate suspensions of diffusive or spatially responsive particles. We present two approaches to encapsulating spatially manipulatable Janus microparticles (JPs), over a broad particle size range (1-50 microns in diameter), within the core of polyurea microcapsules, avoiding substantial Pickering stabilization. Firstly, to make JPs on a sufficient scale, Automated Langmuir Blodgett deposition, where particle monolayers are fabricated on roll-to-roll substrates at meter per minute rates, is used (overcoming the typical rate-limiting step for functionalization). Subsequent particle monolayers are then functionalized through physical vapor deposition (PVD). The first encapsulation approach uses emulsified yield-stress suspensions (JPs in yield stress fluid). This yield stress material is tuned to match the physical properties of the encapsulated microparticles to hinder particle diffusivity, whilst also not permanently fixing particle positions. Particles are actively released through either a temperature change or by manipulation through external forces. A second approach looks at the use of density matching between binary solvents and microparticles to achieve a similar effect without the need for an external activating force. Both methods prove viable over a range of particle sizes and could be applicable to a number of composite microcapsule applications. This work is supported by the Applied Physics Lab at Johns Hopkins University.