Dynamic Laser Prototyping And The Fabrication Of Hydrogel Microstructure

The current micronanofabrication technologies including3D printing technologiesemphasize faithful conversion of CAD model to matter structures. This isindispensable for production of micromechanical, microelectronics, and microopticalcomponents where precise shape and size matter. In these fabrications, environmentalfactors such as polymerization-induced volume shrinkage, the volume expansion, andfluidity of the precursory solution, and temperature gradient are all considered asnegative factors to eliminate. However, for some biomimetic or biologicalfabrications, solely accurate size and shape prototyping is insufficient since thedevelopment of real-world tissues is not only a result of material addition, but aprocess of interactions between grown parts, or between the created structures andenvironments. In another word, the structures are live, and the fabrication processitself matters. From this point of view, a micro-nanoprocessing technology thatpositively involves interactions of environmental factors is necessary. That is whatdynamic laser prototyping does.In this paper, we explore a new micronanofabrication technology called dynamiclaser prototyping. Different from other conventional micronanofabrication technologyseeking faithful conversion of the model to avoid the interference field, so-calledstatic fabrication of microstructure, this method creatively couples the external field.And the process of femtosecond laser direct writing just provides a singletwo-dimensional hydrogel layer with certain shape and thickness, while thethree-dimensional lamellate architectures are completed by the self-organization ofhydrogel. As soon as the hydrogel layer was fabricated, it began to swell by thestimulation of external field. When it reached the threshold, its volume changed andacted as self-organization. Typically, there are three kinds of self-organization,wrinkling, creasing and folding. The size of the single hydrogel layer was very smalland it couldn’t show a surface morphology of self-organization. For the compressive stress was very small, it could be regarded as the wrinkling with only one wavelength.When the sheet was detached from the substrate, the case occurred as the formation ofwrinkling, it first buckled, then made a delamination and released the elastic energy,at last, curled in the free space. As the laser continued, another one would be formedunderneath.Several processing parameters affect the result of the microstructure. Highconcentration of PEG-DA guarantees the morphology of the gel sheet, both thefunctional component AAc and water are responsible for strong self-organizationbehavior. Laser power density and the exposure time on single point correspond to theroughness and couple the time. Whether occurring self-organization or not isdepended on the size and thickness of the single layer.The future development of the dynamic laser prototyping technology has fouraspects:(1) Apply different micronanofabrication technology to form the initialstructure;(2) Introduce different external field;(3) Use different materials orcomposite materials;(4) Place in different environments.