一本道无码

Advances in 3D printing have enabled聽applications across a variety of disciplines like medicine,聽manufacturing 补苍诲听energy. A range of different materials can be used to print both simple foundations and fine details, allowing for the creation of structures with tailored geometries.聽

However, creating structures with microscale, precise internal voids and channels still poses challenges. Scaffolds used in tissue engineering, for example, must contain聽a three-dimensional complex network of conduits that mimic the human vasculature. With traditional additive manufacturing, where the material is deposited layer by layer, it鈥檚 difficult to print such intricate聽internal features without sacrificing time, accuracy and resources.

To address this issue,聽 补苍诲听, professors in mechanical engineering at 一本道无码, are spearheading the development of the freeform 3D ice printing (3D-ICE) process. This technique uses a drop-on-demand 3D printing approach with water as a substitute for conventional printing inks. A piezoelectric inkjet nozzle ejects tiny water droplets onto a build platform maintained below the freezing聽point. This causes the droplets to freeze聽shortly after contact.

Uniquely, the process can be controlled to deposit one or more droplets before the previous droplet is frozen. As such, a water cap remains atop the printed structure, and the freezing progresses from the bottom. This enables the creation of structures with smooth walls, transitions and branches. Features as small as human hair can be fabricated. As more droplets are deposited, an聽ice structure takes shape on the build platform. The diameter, height and relative smoothness of the pillar鈥檚 geometry can be adjusted by聽controlling the rate of droplet deposition,聽and the temperatures of the printing surface, droplet and workspace.聽If the build platform is shifted such that the incoming droplet hits at an angle, the freeze front will rotate accordingly, making it possible to produce branching, curved and overhanging structures that would be challenging or聽impossible to print with聽alternative 3D printing techniques without extra support materials.

鈥�3D ice could be used as a sacrificial material, which means we could use it to create precisely shaped channels inside of fabricated parts,鈥� said LeDuc. 鈥淭hat would be useful in a lot of聽areas, from creating new tissues to soft robotics.鈥�

Since the聽 of their project, LeDuc and Ozdoganlar鈥檚 research team has investigated ways to ensure that the 3D ice process is predictable and reproducible. In their recent article published in聽the , they describe 2D and 3D numerical models to elucidate the physics behind 3D ice, including heat transfer, fluid dynamics and the rapid phase change from liquid to solid during the printing process.

Their 2D models map the construction of straight pillars, including the respective effects of layered and smooth deposition. 鈥淭he frequency of droplet deposition affects the height and width of the structure,鈥� said Ozdoganlar. 鈥淚f you deposit quickly, the water cap grows, producing wider structures. If you deposit slowly, then聽the structure becomes narrower and taller. There are also effects from the substrate temperature. For the same droplet聽deposition rate,聽a lower substrate temperature produces taller structures.鈥�

Their 3D models map the construction of oblique structures by predicting the rotation of the freeze front. 鈥淵ou have all types of heat transfer, including conduction to the bottom and convection to the surrounding area,鈥� said Ozdoganlar. 鈥淎ll those things are working simultaneously when you deposit each droplet. If you deposit obliquely, part of the droplet spills over on the side of the pillar before it freezes. And as you keep depositing at that angle, the freeze front slowly changes shape, and the structure grows in that direction.鈥�

In addition to further refining their mathematical models, LeDuc and Ozdoganlar鈥檚 labs聽are now looking to scale up 3D-ICE and explore its efficacy across a range of applications. For instance, current strategies in tissue engineering often involve designing generalized tissues. 3D-ICE could soon make it possible to print personalized tissues that match the unique structure of each patient鈥檚 vasculature, meeting the specific needs of the patient鈥檚 body. Moreover, 3D-ICE will enable the creation of functional tissue constructs for use in understanding different diseases or developing new therapeutics.

鈥淲hen I first started my lab, I would never have imagined that聽we would be 3D printing ice, and using聽it to create tissues聽to help people,鈥� said LeDuc. 鈥淏ut our research has evolved. It has brought people like Burak and myself together, and everyone brings all sorts of different perspectives 补苍诲听capabilities to the table. It鈥檚 a wonderful thing to do this work聽together where the sum of the parts is definitely greater than the individual parts in this transdisciplinary science and engineering.鈥�