3-D Non-UV Digital Printing of Hydrogel Microstructures by Optically Controlled Digital Electropolymerization

A technique using digital masks without ultraviolet light to rapidly print 3-D biopolymer structures with complex microarchitectures in a microfluidic chip has been demonstrated. In this approach, a customized system is used to project light images on a photoconductive substrate in order to create localized virtual electrodes when an alternating electric field is applied across the fluidic medium in an optically controlled digital electropolymerization chip. Upon these virtual electrodes, the localized electric fields are generated, which could activate the polymerization of acrylate-based molecules, such as poly(ethylene glycol) diacrylate (PEGDA), to form microstructures with the same shapes as the projected light images. We have demonstrated that the 3-D PEGDA microstructures with the customized shapes could be fabricated rapidly through a layer-by-layer process by applying a series of digital masks (projected light images). With our current projection and microscopy system, the fabrication of microhydrogel structures with a lateral resolution of 3 μm and an adjustable thickness ranging from tens of nanometers to hundreds of micrometers has been demonstrated. In summary, this novel technique provides an efficient process for the rapid printing of the 3-D biopolymer-based microstructures, and could enable many future applications in a mechanoanalysis of cancer cells, tissue engineering, and drug screening.