title: A 'microfluidic pinball' for on-chip generation of Layer-by-Layer polyelectrolyte microcapsules.
abstract: Inspired by the game of "pinball" where rolling metal balls are guided by obstacles, here we describe a novel microfluidic technique which utilizes micropillars in a flow channel to continuously generate, encapsulate and guide Layer-by-Layer (LbL) polyelectrolyte microcapsules. Droplet-based microfluidic techniques were exploited to generate oil droplets which were smoothly guided along a row of micropillars to repeatedly travel through three parallel laminar streams consisting of two polymers and a washing solution. Devices were prototyped in PDMS and generated highly monodisperse and stable 45±2 µm sized polyelectrolyte microcapsules. A total of six layers of hydrogen bonded polyelectrolytes (3 bi-layers) were adsorbed on each droplet within <3 minutes and a fluorescent intensity measurement confirmed polymer film deposition. AFM analysis revealed the thickness of each polymer layer to be approx. 2.8 nm. Our design approach not only provides a faster and more efficient alternative to conventional LbL deposition techniques, but also achieves the highest number of polyelectrolyte multilayers (PEMs) reported thus far using microfluidics. Additionally, with our design, a larger number of PEMs can be deposited without adding any extra operational or interfacial complexities (e.g. syringe pumps) which are a necessity in most other designs. Based on the aforementioned advantages of our device, it may be developed into a great tool for drug encapsulation, or to create capsules for biosensing where deposition of thin nanofilms with controlled interfacial properties is highly required.
authors.affiliation: Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), 11 Science Park Road, Science Park II, 117685, Singapore.
authors.forename: Chaitanya
authors.initials: C
authors.lastname: Kantak
authors.forename: Sebastian
authors.initials: S
authors.lastname: Beyer
authors.forename: Levent
authors.initials: L
authors.lastname: Yobas
authors.forename: Tushar
authors.initials: T
authors.lastname: Bansal
authors.forename: Dieter
authors.initials: D
authors.lastname: Trau
mesh_terms: D000327:Adsorption; D002214:Capsules / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D018625:Microscopy, Atomic Force
chemical_list: D002214:Capsules; D004573:Electrolytes; D008670:Metals