Session: 16-01-01: Poster Session: NSF-Funded Research (Grad & Undergrad)

Paper Number: 100237

100237 - A Novel Multi-Material Printing Using Static Immiscible Oil as Process Window 

The stereolithography (SLA) and digital light processing (DLP) printing process fabricates 3D forms by incorporating light source to cure liquid polymers. The common DLP method uses resin-in-vat, an actuated print platform on top, and a solid transparent fluorinated ethylene propylene (FEP) or polydimethylsiloxane (PDMS) window interface on the bottom of the vat to project a UV pattern onto the resin layer by layer. The common method suffers from stiction issue from the solid transparent window once the polymer resin cures from UV exposure. The stiction issue can damage the window and cause print failure.

My research incorporates a static, immiscible, perfluorinated polyether inert fluid as a process window interface to solve the stiction issue and ultimately conduct a multi-material printing. The experiment uses a new vat design to retain the immiscible oil and a controllable fluidic system to laterally flow and switch different resins.  Preliminary results show that a single type of resin can be printed in an octet lattice structure and easily detached from the fluidic window. Upon each layer exposure, the discrete printing method uses an up-and-down recoating process from the printing stage to allow the resin to be refilled under the cured part. The recoating process mitigates a significant cavitation development between the window and emerging parts. In addition to the discrete printing, a continuous printing was successfully conducted, where the print stage does not incorporate the recoating process and rather continuously moves up while the shape of the UV exposure is changing. Despite some cavitation formations among layers, the proper control of UV exposure, print stage, and resin formulation was able to print the octet lattice structure at a size of 22 mm x 22 mm x 10 mm. The printing speed on the continuous printing was achieved at 43 microns per seconds. It can also theoretically be increased to the max speed of 125 microns per seconds. After obtaining the preliminary results, I now investigate towards printing multi-material structure using the static, immiscible oil as process window.

Understanding the material switching process and cleansing process are very important in developing a rapid, high throughput multi-material printing method that uses an immiscible oil interface and a controllable fluidic system. This new experimental technique will flow one material into the vat, expose it with a UV pattern, then cleanse it with ethanol, then flow a second material into the vat, expose it with a UV pattern, then cleanse it with ethanol to move to the next layer. The uncured resins will be sorted so that it can be recycled. Preliminary experimental results on the multi-material printing show that there is a contamination issue between the two materials. The contamination is mainly caused by sharing the two-way valve to flow the two materials into the vat and by not efficiently cleansing the initial material. A thorough investigation of the material switching process into and out of the vat is required to successfully print a multi-material structure. A development of the novel multi-material additive manufacturing method will open more ways to rapidly fabricate and reliably utilize multi-material structures.

Presenting Author: David Hahn UCLA

Presenting Author Biography: 1st Year Mechanical Engineering PhD Student at UCLA in the Additive Manufacturing and Metamaterials Lab.

Authors:

David Hahn UCLA
Zhenpeng Xu UCLA
Xiaoyu Zheng UCLA