title: Steering air bubbles with an add-on vacuum layer for biopolymer membrane biofabrication in PDMS microfluidics.
abstract: Membrane functionality is crucial in microfluidics for realizing operations such as filtration, separation, concentration, signaling among cells and gradient generation. Currently, common methods often sandwich commercially available membranes in multi-layer devices, or use photopolymerization or temperature-induced gelation to fabricate membrane structures in one-layer devices. Biofabrication offers an alternative to forming membrane structures with biomimetic materials and mechanisms in mild conditions. We have recently developed a biofabrication strategy to form parallel biopolymer membranes in gas-permeable polydimethylsiloxane (PDMS) microfluidic devices, which used positive pressure to dissipate air bubbles through PDMS to initiate membrane formation but required careful pressure balancing between two flows. Here, we report a technical innovation by simply placing as needed an add-on PDMS vacuum layer on PDMS microfluidic devices to dissipate air bubbles and guide the biofabrication of biopolymer membranes. Vacuuming through PDMS was simply achieved by either withdrawing a syringe or releasing a squeezed nasal aspirator. Upon vacuuming, air bubbles dissipated within minutes, membranes were effortlessly formed, and the add-on vacuum layer can be removed. Subsequent membrane growth could be robustly controlled with the flows and pH of solutions. This new process is user-friendly and has achieved a 100% success rate in more than 200 trials in membrane biofabrication.
authors.affiliation: Department of Mechanical Engineering, The Catholic University of America, Washington, D.C. 20064, USA. luox@cua.edu.
authors.forename: Phu
authors.initials: P
authors.lastname: Pham
authors.affiliation: Department of Mechanical Engineering, The Catholic University of America, Washington, D.C. 20064, USA. luox@cua.edu.
authors.forename: Thanh
authors.initials: T
authors.lastname: Vo
authors.affiliation: Department of Mechanical Engineering, The Catholic University of America, Washington, D.C. 20064, USA. luox@cua.edu.
authors.forename: Xiaolong
authors.identifier: 0000-0002-9939-2766
authors.initials: X
authors.lastname: Luo
mesh_terms: D000388:Air; D004129:Dimethylpolysiloxanes; D056656:Lab-On-A-Chip Devices; D008567:Membranes, Artificial; D010539:Permeability; D014618:Vacuum
chemical_list: D004129:Dimethylpolysiloxanes; D008567:Membranes, Artificial; C013830:baysilon