Facile method for 3D printing conformally onto uneven surfaces and its application to face masks.

Conventional additive manufacturing processes, where parts are built through layer-wise deposition of material on a horizontal plane, can be limiting when a part must be printed or fit onto uneven surfaces. Such situations will arise with increasing frequency as additive manufacturing application areas such as construction and medical devices continue to grow. In this work, we develop a simple and practical approach to generate toolpaths to print 3D structures onto uneven surfaces conformally. The algorithm uses only conventional planar toolpaths of both the structure to be printed and the substrate to be printed on and converts these to non-planar toolpaths, allowing easy integration with existing additive manufacturing workflows. The technique is demonstrated by printing flexible seals onto bespoke rigid face mask frames conformally via a conventional single-material 3D printer using the generated conformal toolpath. A notable improvement in air seal performance was observed for customized face masks with conformal soft seals compared to conventionally 3D-printed fully rigid face masks. This also shows the potential of the developed toolpath generation method to aid in the prototyping and fabrication of conformal medical and other devices.

Elastic Bioresorbable Polymeric Capsules for Osmosis-Driven Delayed Burst Delivery of Vaccines.

Single-administration vaccine delivery systems are intended to improve the efficiency and efficacy of immunisation programs in both human and veterinary medicine. In this work, an osmotically triggered delayed delivery device was developed that was able to release a payload after a delay of approximately 21 days, in a consistent and reproducible manner. The device was constructed out of a flexible poly(ε-caprolactone) photo-cured network fabricated into a hollow tubular shape, which expelled approximately 10% of its total payload within 2 days after bursting. Characterisation of the factors that control the delay of release demonstrated that it was advantageous to adjust material permeability and device wall thickness over manipulation of the osmogent concentration in order to maintain reproducibility in burst delay times. The photo-cured poly(ε-caprolactone) network was shown to be fully degradable in vitro, and there was no evidence of cytotoxicity after 11 days of direct contact with primary dermal fibroblasts. This study provides strong evidence to support further development of flexible biomaterials with the aim of continuing improvement of the device burst characteristics in order to provide the greatest chance of the devices succeeding with in vivo vaccine booster delivery.