Rapid Digital Light 3D Printing Enabled By A Deformable Hydrogel Separation Interface

3D printing is a new manufacturing technology with rapid development in recent years.However,compared with traditional manufacturing methods,its production efficiency is still low,which limits its large-scale application.Among them,Digital Llight Processing(DLP)is based on layer-wise printing,which stands out in a faster printing speed at the same precision and has a higher degree of market acceptance.But at present,the printing speed of DLP still can not meet the needs of mass production.One of the main reasons is that the printing part adheres to the projection window during the printing process,and the separation speed needs to be reduced to avoid parts damage and sticking to the bottom.To solve this problem,the commercial strategy is to use the Fluorinated Ethylene Propylene(FEP)release film as the curing interface,but the separation force is still excessive,and it is not suitable for the building large-size continuous structure parts.To break through the limitation of printing speed,some innovative technologies have been developed in academia,but often need complex equipment support or high use cost,which greatly limits its industrial development.It is of great significance to develop a new type of release material in view of the problem that the printing speed is compromised due to the large separation force.In this work,based on the most common DLP 3D printer,we use green cheap hydrogel instead of FEP release film as the curing interface,and use its soft and deformable characteristics to reduce the separation force between the cured resin and the release surface.It has the effect of simplifying the separation process and improving the separation speed,thus significantly improving the printing speed.Specifically,after optimizing the modulus and thickness of the hydrogel,the separation force can be reduced to 1/4 of the FEP release film,and the ultra high speed printing of 400 mm/h can be achieved.At the same time,the technology shows excellent printing stability,and can be used to prepare large-scale continuous solid structures which are challenging to obtain by other rapid 3D printing processes.To demonstrate the universality of hydrogel as curing interface,we prepare three functional 3D printing materials:elastomer,casting resin,and shape memory polymer.The elastomer is based on polyurethane acrylate,which has low modulus and can not be printed by common bottom-up DLP printers.The hydrogel interface reduces the force in the pull-up process and even makes it possible for rapid manufacturing.The casting resin has certain hydrophilicity,but can still be used stably.This material is suitable for rapidly making delicate metal products combined with casting process.The shape memory polymer is prepared by polymerizing several commonly used acrylates,and its shape memory transition temperature can be programmed flexibly by changing the chemical composition of the ingredients.Combined with the advantages of our rapid printing technology,this material can promote the development of 4D printing technology.