Focused Electron and X-ray Beam Crosslinking in Liquids for Nanoscale Hydrogels 3D Printing and Encapsulation

Additive fabrication of biocompatible 3D structures out of liquid hydrogel solutions has become pivotal technology for tissue engineering, soft robotics, biosensing, drug delivery, etc. Electron and X-ray lithography are well suited to pattern nanoscopic features out of dry polymers, however, the direct additive manufacturing in hydrogel solutions with these powerful tools is hard to implement due to vacuum incompatibility of hydrated samples. In this work, we resolve this principal impediment and demonstrate a technique for in-liquid hydrogel 3D-sculpturing separating high vacuum instrumentation and volatile sample with ultrathin molecularly impermeable membranes transparent to low-energy electrons and soft X-rays. Using either scanning focused electron or synchrotron soft X-ray beams, the principle of the technique, particularities of the in-liquid crosslinking mechanism and factors affecting the ultimate gel feature size are described and validated through the comparison of experiments and simulations. The potential of this technique is demonstrated on a few practical examples such as encapsulation of nanoparticles and live-cell as well as fabrication of mesoscopic 3D-hydrogel structures via modulation of the beam energy