The invention describes the method of the patterning of hydrogels in liquid (native) sate through electron (x-ray) transparent membranes. Such a membrane is molecularly impermeable (or partially permeable) separates the electron and x-ray optics from the high pressure ambient of the sample. Strong dependence of the attenuation length of electrons and, x-ray radiation in a dense medium on energy is used for controlled crosslinking of liquid polymer solution to fabricate 2-and 3-dimensional gel structures with submicron spatial resolution. The key advantage of the method compare to prior dry gel patterning is ability to micropattern gel solution in its liquid state. This allows for additive fabrication of multi-compositional 2D and 3D-gel constructs (e.g. for tissue or soft robotics engineering etc.), addressable gel-encapsulation of the objects of interest (e.g. drugs, biomolecules, functional nanoparticles), gel-coating and patterning of functional entities such as live biological objects, composites, electrochemical electrodes etc.
The fabrication of 2D and 3D structures out of liquid biocompatible hydrogel solutions has become pivotal technology for tissue engineering, soft robotics, biosensing, drug delivery, wounds treatment and biomedical research in general.
State-of-the-art additive manufacturing from liquid gels is based on photoinduced crosslinking of the polymer solution and therefore is limited to micron level spatial resolution by the diffraction limit of the optics. The obvious direction to improve resolution would be to use electrons or X-rays as the trigger as they can have much smaller wavelength and mean free path in a dense matter which can also be controlled by their energy. However, state- of the art e-beam and X-ray lithography is essentially 2D process which requires vacuum conditions and therefore dry samples. and lacks the potential to perform truly 3D printing in a continuous process. In the disclosed invention, we overcome this barrier via the use of an electron and X-ray transparent membrane, which isolates the vacuum of the radiation chamber source from the liquid sample.
In our invention, the electron or X-ray beam penetrates in to the liquid after passing through the membrane and crosslinks the polymer molecules in the liquid solution within the interaction volume. The spatial resolution of this technique mainly depends on the size of the interaction volume, which in turn is a function of electron/x-ray energy and can be tuned from 10 nm to tens of microns. In addition, the structure size and degree of the crosslinking can be controlled by the additional set of parameters such as: irradiation dose (flux, exposure time, dwell time, pitch size in case of scanning), temperature (diffusion), concentration of the solute.