Hybrid additive-subtractive laser fabrication platform for shaping hydrogels

Statement of Purpose. Sculpting and shaping hydrogels into complex multiscale functional devices remains challenging [1]. In recent years, additive fabrication methods have been used to print hydrogel constructs, however creating multiscale hydrogel-based devices with three dimensional (3D) internal features remains difficult. Ultrafast lasers have revolutionized the processing of hydrogels due to its unique property of nonlinear multiphoton absorption [2]. Although ultrafast lasers have been used in both additive crosslinking and subtractive ablation modes, efforts to combine these two well established methods into a single versatile manufacturing platform have been difficult due to (i) material incompatibilities and/or significant differences in laser processing requirements of the two processes, (ii) use of photoresist that are not compatible with living cells or mechanically weak and difficult-to-print biomimetic hydrogels, (iii) limited scalability in the z-direction due to low laser penetration depth, associated with the optical absorption/scattering properties of hydrogels [3]. In this work, we report the design and development of a new hybrid laser printing (HLP) method that allows processing of multiscale hydrogel-based constructs that cannot be fabricated with existing techniques and potentially enable new research applications in biomedical sciences.