Month: September 2017

New research from Ian Wong‘s group at Brown University published in Lab on a Chip and featured in a Technology Networks article shows 3-D printed microfluidic devices with on-demand degradation of substrate materials.  Not only does this allow for easy fabrication of complex structures, but also allows for them to be controllably modified ‘on the fly’.  The key is in the use of reversibly photopolymerisable hydrogels with ionic cross-linkers.  Cross-linkers can then be removed with chelating agents.  The stiffness and degradation kinetics are controllable by the choice of metal cation for the ionic cross-linker.  Both the sodium alginate ionic cross-linking polymer and chelating agents chosen appear to be biocompatible with the human mammary cells used in the study.

While normally used to directly create the microfluidic structures, the reversible gels were also used in a second approach to create complex moulds that are removed after a second polymer forms around the reversible gel.

The technology may potentially be applied as an adaptive or stimulus responsive material for use in sensing, actuation, drug delivery, cell migration monitoring for wounds or cancer, artificial tissue scaffolding or other applications.

An interesting  Cytofluidix post highlights recent work by a collaborative team of researchers at both Singapore’s A*STAR’s SIMTech facility and Nanyang Technological University, and at the Seoul National University of Science and Technology, based on their article published in the Journal of Materials Processing Technology.

The focus is on addressing the drawbacks encountered with ultrasonic welding as a bonding technique for plastic microfluidic devices.  Ultrasonic welding is attractive because it lends itself to batch processing of microfluidic devices, and employs relatively established, inexpensive and compact equipment.  As currently used, however, ultrasonic welding is often not up to the task, from a quality perspective, since uneven energy distribution may distort or melt the microfabricated structures, and air bubbles may also be incorporated.

According to Gary Sum Huan Ng from the SIMTech group, the team’s innovation is to introduce a sandwiched composite film between the two polymer substrates that are to be bonded.  The film contains PMMA microspheres within a PDMS matrix, and the microspheres melt during ultrasonic welding, and prevent bubble formation and substrate material flow.