Researchers fromStanford University和Harvard Universityhave developed a new method of volumetric 3D printing capable of fabricating resin parts without the need for any support structures.
这种方法依赖于nanoparticle-laden树脂material that only hardens when it’s blasted with a very focused laser spot. By varying the focus of the laser throughout the resin vat, the researchers have made it possible to print at any point in the pool of resin, not just at the surface layer.
因此，新颖的3D打印机不一定需要从逐层打印对象，从而为可以从任何方向“添加”的抽象几何形状铺平了道路。
这项研究的合着者丹·康格雷夫（Dan Congreve）说：“因为我们的树脂在印刷过程中是自支撑的，所以我们不需要打印任何支撑物，可以使零件的后处理变得更加简单。”“因为我们不仅限于这个逐层过程，因此我们可以打印诸如传统上具有挑战性的悬垂结构。这是一项全新的技术，我们才刚刚开始刮擦它的能力。”
Light-converting nanoparticles for 3D printing
On first inspection, the Stanford 3D printing method looks a lot like conventional stereolithography (SLA). A laser beam is directed at resin in a vat, which cures when it’s exposed to blue light. However, the team didn’t just use a standard blue laser as this would cure the resin along the entire length of the penetrating beam.
取而代之的是，他们利用了一个特殊的树脂，该树脂含有直径仅80nm的光转换纳米颗粒。当临界能量阈值受到命中时，纳米颗粒的设计目的是将红光转换为蓝光，只有在激光处于最大焦点处时才能实现。因此，该技术使用标准的红色激光器，具有稀释和聚焦红色激光器的机制。
新颖的设置消除了仅在表面层上固化的需求，从而可以通过仅将红色激光器聚焦在所需的XYZ坐标处来治愈树脂增值税中的单个点。团队指出，一个或多个激光器可以围绕增值税旋转以同时从每个方向上打印，从而实现任何几何形状，而无需支撑。
Triplet fusion upconversion
The mechanism for transforming one wavelength of light into another is called triplet fusion upconversion and it’s Congreve’s specialism.
“I got interested in this upconversion technique back in grad school,” he adds. “It has all sorts of interesting applications in solar, bio, and now this 3D printing. Our real specialty is in the nanomaterials themselves – engineering them to emit the right wavelength of light, to emit it efficiently, and to be dispersed in resin.”
To formulate the special resin mix, the team turned the active upconversion molecules into nanoscale droplets and coated them in a shielding silica layer. The resulting nanocapsules were distributed throughout the resin matrix to form the final light-converting composite.
“Figuring out how to make the nanocapsules robust was not trivial – a 3D-printing resin is actually pretty harsh,” said Tracy Schloemer, one of the lead authors of the study. “And if those nanocapsules start falling apart, your ability to do upconversion goes away. All your contents spill out and you can’t get those molecular collisions that you need.”
The researchers are currently in the process of exploring other applications for the light-converting nanocapsules. Potential use cases include more efficient solar panels, whereby low-energy light can be converted into a wavelength that solar cells can more easily capture. They can also be used to study biological models that use light to power chemical reactions.
更多细节的研究可以发现paper titled‘Triplet fusion upconversion nanocapsules for volumetric 3D printing’.
Despite the novelty of their 3D printer, the Stanford researchers aren’t the first to explore the concept of volumetric 3D printing. A research team fromUtrecht University最近，使用了newly developed ultrafast volumetric 3D bioprinting method. Printed in less than 20 seconds, the liver units were able to perform key toxin elimination processes mimicking those that natural livers perform in our bodies, and could open new opportunities for regenerative medicine and personalized drug testing.
Elsewhere, a research team led byUniversity College London(UCL) recently used体积的3D打印以制造吸毒平板电脑据报道，在几秒钟内，第一次。该团队在17秒内成功生产了帕酰甲氨基酚的片剂，这比在研究和某些临床环境中打印药品的当前方法要快得多。
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Featured image shows a tiny resin benchy 3D printed by the Stanford researchers. Photo via Dan Congreve.
