3D and 4d bioprinting: additive manufacturing of smart biodegradable hydrogels
The controlled behaviour of biological systems in response to external stimuli is ubiquitous in nature and perceived as a key requirement for the development of advanced functional materials. A good example found in nature is the so-called “sensitive plant” (Mimosa) that responds to touch by rapidly closing its leaves, as a defense mechanisms against herbivores. This quick response to touch is due to rapid water release from specialized cells located at the leaves. In attempt to mimic nature, 4D-BIOGEL project aims to combine new fully biodegradable water-filled hydrogels with additive manufacturing or 3D printing to design smart materials that can undergo a temporal change in their shape under the influence of an external stimulus, giving a 4th dimension to the previously designed 3D object. Light-sensitive structures activated by near-infrared (NIR) are especially appealing, since light can be conveniently pinpointed to the location of interest with the maximum depth of penetration and the minimum damage of tissues. To obtain NIR-sensitive hydrogels, nanoparticles capable of converting light into heat will be incorporated into the hydrogel matrix to afford small volume contraction-expansion changes on demand. This advanced technology offers great potential for the creation of sophisticated dynamic structures with high resolution that could find application not only in regenerative medicine or drug-delivery, but also in robotics or bioelectronics. 
The 24-month outgoing phase will take place at the University of Washington in Seattle, under the supervision of Dr. Alshakim Nelson - one of the top-class researchers in 3D and 4D printing of hydrogels. The final goal is that during the third year of the fellowship, under the guidance of Dr. Haritz Sardon at the University of the Basque Country in Spain (BERC-POLYMAT), Dr. Eva Sanchez can translate all the expertise acquired about the innovative fields of 3D and 4D bioprinting to Europe, where there is a clear need.