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New Technique Creates Smoother 3D Printed Optical Components

STL file of a parabolic mirror

3D printed objects don’t come off the print bed perfectly smooth; on the contrary, many 3D printing technologies leave a decent amount of surface roughness, which is unacceptable for applications involving optics. These applications may include mirrors, lenses, and solar panels, just to name a few. It would be easy to write off 3D printing as a method of producing these optics, but there are ways around the issue, as Stanford University researchers Nina Vaidya and Olav Solgaard demonstrate in a new paper entitled “3D printed optics with nanometer scale surface roughness.” You can access the full publication here.

3D printing is, in fact, an appealing option for 3D printing optics, as it allows for fast and cheap production of geometries that other methods of fabrication are not capable of. The rough surfaces of 3D printed objects, however, create scattering, which reduces optical performance. The Stanford researchers developed a UV curable polymer mixture that they applied to the surface of 3D printed parts, which reduces the surface roughness to a few nanometers as opposed to tens of microns.

3D printed parabolic mirrors at different stages of the fabrication process: As printed (a), after smoothing (b), and the completed mirror after smoothing and Al deposition (c)

“We tried a number of smoothing techniques, including flame polishing, acetone vapor polishing, spraying of polymer coatings, and mechanical polishing,” the researchers explain. “None of these methods create the nanometer scale smooth surfaces required for optical applications. To meet this surface roughness criterion, we coated the printed optics with a UV curable polymer mixture consisting of methacrylates, acrylates, and urethane based polymers. This gel resulted in smooth and tough films that adhered well to the printed surfaces. When compared to a heat cure, a UV cure minimizes shrinkage of the polymer, which maximizes surface smoothness and conformal coverage.”

Solar concentrator lens array: The input side is arranged as a tileable array of hexagons that along the length of the concentrators gradually morph into squares on the output side. The smaller squares at the output allow smaller solar cells to be used to convert the concentrated power. The molds were filled with graded-index polymers to complete the concentrator array. Figures a–d show the process flow from as-printed part to the completed concentrator array

The process takes several steps:

  • Rinse the 3D printed part with water and detergent, blow dry and leave in low temperature oven
  • Place the part in a vacuum to de-gas for a few hours
  • Coat a thin layer of UV curable polymer mixture on the surface of the part with a fine brush
  • Place in vacuum chamber to get rid of any air trapped in the printed material, in the gel layer, or in between the printed surface and the gel so that the gel can fill in any pores or depressions to make smooth surfaces
  • If needed for conformal coverage, use gravity or spinning to remove excess gel. Let gel flow under gravity by placing the optics flat on a stand. Spin at around 1400 rpm for 3–5 min while the gel is still un-cured. Brush off excess gel at the edge of the frame/support
  • UV cure the finished gel surface for a couple of minutes, with the exact time depending on the size of the part

The researchers tested their technique with both flat and parabolic mirrors, solar concentrator arrays, and immersion lenses used in microscopy of biological samples. Consistently, they were able to reduce the surface roughness to less than three nanometers after the smoothing process.

“Imaging with 3D printed parabolic mirrors were comparable to a diamond turned metal mirror and nearly diffraction-limited spot sizes were measured with modest incidence apertures,” the researchers state. “Solar concentrator hexagonal arrays were made using 3D printing and they demonstrated 5 suns concentration across an acceptance angle of 40°. PDMS immersion lenses were made with nanometer smooth surfaces released from 3D printed molds.”

3D printing has been used before to manufacture optical components, typically using highly specialized equipment to get the kind of surface needed. Vaidya and Solgaard tested multiple 3D printing technologies and found that SLA and wax printers were the most effective for creating optical components, as long as the smoothing solution was applied afterwards. Their method enabled them to produce optics that were low-cost, customizable, lightweight, low on material waste and easy to fabricate.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

 

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Stanford 3D Print Smoother Optical Components Using New Technique

3D printing optics would be very advantageous for many companies due to the inherent speed and cost efficiency of the system. However, the one issue that makes it entirely undesirable is that of print quality, which lends itself to surface roughness. Many printed optics create scattering as a result of this lack of consistency. Although, […]

The post Stanford 3D Print Smoother Optical Components Using New Technique appeared first on 3D Printing.

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Motorbikes, ships, scandium and NDT: inside Additive Manufacturing journal Oct. 2018

As seen from the highly efficient 3D printed batteries at Carnegie Mellon University (CMU) and Missouri University of Science and Technology, the October 2018 edition of ScienceDirect’s Additive Manufacturing journal is now in progress. Volume 23 currently includes the work of 9 innovative research groups from leading institutions all around the world, including projects from the Fraunhofer Institute for Laser Technology (ILT), the University of Cádiz and […]
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UBOT P440 3D printer technical specifications, pricing and insights from COO

High-performance thermoplastic materials such as PEEK, PEI, and PETG are accelerating the use of industrial 3D printing allowing the creation of functional parts for rapid prototyping, tooling, final part production, and customization. However, such materials are beyond the reach of many FFF/FDM 3D printers due to the higher temperatures required. UBOT 3D, a Polish 3D printer […]
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Low Poly World Map

What an interesting way to create a map.

via Bewegingslab on Thingiverse

After printing laydown the map on a table. This way you kan compare the pieces with the complete image from Thingiverse. Tape a frame from 96cm wide and 55 cm heigh, so you can position the pieces en glue them on.

See more of this design.

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Researchers 3D Print Clamping Systems to Cut Down on Slippage During Soft Tissue Testing

When I think about clamps, if I do at all, it’s in terms of holding wood steady in a scene shop while making sets for a play, or keeping two large objects that have been glued together tight while the glue dries. But there are many different purposes and applications for clamps, including in the medical field, demonstrated by the 3D printed cardioplegia clamps designed for King’s College Hospital Foundation Trust two years ago.

Recently, a collaborative group of researchers from the University of Otago and the Auckland University of Technology in New Zealand and the University of Leipzig in Germany published a paper, titled “Utilization of 3D printing technology to facilitate and standardize soft tissue testing,” in the Scientific Reports journal that detailed their work in creating 3D printed clamps and fixtures that can help mount soft tissues for testing purposes.

The abstract reads, “This report will describe our experience using 3D printed clamps to mount soft tissues from different anatomical regions. The feasibility and potential limitations of the technology will be discussed. Tissues were sourced in a fresh condition, including human skin, ligaments and tendons. Standardized clamps and fixtures were 3D printed and used to mount specimens. In quasi-static tensile tests combined with digital image correlation and fatigue trials we characterized the applicability of the clamping technique. Scanning electron microscopy was utilized to evaluate the specimens to assess the integrity of the extracellular matrix following the mechanical tests. 3D printed clamps showed no signs of clamping-related failure during the quasi-static tests, and intact extracellular matrix was found in the clamping area, at the transition clamping area and the central area from where the strain data was obtained. In the fatigue tests, material slippage was low, allowing for cyclic tests beyond 105 cycles. Comparison to other clamping techniques yields that 3D printed clamps ease and expedite specimen handling, are highly adaptable to specimen geometries and ideal for high-standardization and high-throughput experiments in soft tissue biomechanics.

Soft tissues have several special characteristics, such as being diverse, directionally dependent (anistropic), and viscoelastic (exhibiting both viscous and elastic characteristics when undergoing deformation). The power of these qualities is increased by things like post-mortem delay, water content alterations, and traumatic pathology, all of which can cause issues when it comes to standardized mechanical tests of the tissue under strain.

Fixtures and clamps have been used to help with issues like material slippage, but are limited when working with soft tissue due to reasons like, as the paper lists, “avulsion at the clamping site or the risk of temperature-induced changes in the mechanical behavior.”

Over the last few years, the team developed a technique called partial plastination that uses ceramic-reinforced polyurethane resin at the clamp mounting sites to help with slippage. But it takes a long time to prepare this method, which also requires special (read expensive and hard to come by) equipment like casting fixtures and vacuum pumps, and errors can come up during the clamping due to how difficult it can be to position soft tissues in a test that involves the effects of gravity.

“As a consequence, we aimed to explore alternative techniques which may facilitate tissue clamping, and aid in standardizing the clamping of soft tissues for biomechanical testing in a less time-consuming manner,” the researchers explained in their paper. “3D printing has meanwhile become broadly available, and such professional extrusion solutions can be utilized for customizing and printing fixtures and adjustments for biomechanical testing using commercially-available filaments. Furthermore, it can be utilized to provide affordable add-ons to existing testing devices all over the world, going beyond just soft-tissue biomechanics. The possibility of sharing existing digital models enables a broad availability and exchange of research and knowledge. 3D printing may also be used for clamping mechanisms, and variations in clamping design appear to be eased by the rapid-prototyping approach with the ubiquitously-available software.”

Standardization in material testing and test setup. Focus of this study will be the boxes highlighted in red.

During a quick Internet search, I found models of 3D printable clamps on Thingiverse, Instructables, and 3D Hubs, though none were for medical purposes. The research team’s clamping systems were designed using Creo 4.0 3D CAD software, and printed on an Ultimaker 3 Extended in commercially available ABS, PLA, nylon, and TPU filaments.

In their paper, the research team described their experience mounting human soft tissues, from three different anatomical regions with differing properties, using 3D printed clamps, and also compared this new way of clamping to their previous partial plastination method.

Co-authors of the paper are Mario Scholze, Aqeeda Singh, Pamela F. Lozano, Benjamin Ondruschka, Maziar Ramezani, Michael Werner, and Niels Hammer.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.

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Daniel A Tillman on 3D Printing In Education

The work of Daniel A Tillman, Professor in Educational Technology, College of Education at the University of Texas at El Paso centers around educating children and technology. Professor Tillman has been writing about using 3D printing and other digital fabrication tools in the classroom since 2009. He writes about how fablabs, AR, 3D printers and music can help kids learn math. 3D Printing has often been touted as a resource for educators and children alike. Most of the people talking about education and 3D printing have a vested interest in presenting it as a panacea. We continually here that this or that amazing 3D printing project is going to help kids and see lots of happy kids with 3D printers. But, can 3D printing actually help kids learn? What are actual findings? Is 3D printing amazing for education, allways, for everyone? At 3DPrint.com we were curious to see if a more nuanced view was possible and so we searched for someone who had considerable research in the classroom with various technologies including 3D printing. We found Professor Tillman’s work on the pedagogical value of digital fabrication, letting kids make musical instruments to learn math and using makerspaces in education and turned to him for that nuance through an interview.

 

 

 

In workshops I’ve organized I’ve used 3D printed parts and files to illustrate the “why” for math as well as how it combines the screen and the real. Is that something you feel 3D printing can do?

3D printing is a great way to introduce students to design and engineering, and if they pursue those interests they will certainly encounter the “why” for math–but if a kid sees a 3D printer in action and isn’t interested, because they are instead focused on music or sports or painting etc then the 3D printing is just like a microwave to them, a useful tool perhaps but not likely to convince them they need math if their goal is to become a guitarist.

I’ve always felt that when giving workshops that kids can really grasp concepts better if they can hold the 3d print. Do you think that this is something that could benefit a lot of kids?

I’ve met many kids and teachers that find 3D printing to be fascinating and instructional, and other kids and teachers that weren’t too impressed–so yes, it can help a lot of kids, maybe even the majority of kids, but it is not a one-size-fits-all solution for getting all kids excited about math or convincing them math is helpful.

Things such as diagrams or maps of battles are often complex to read. Wouldn’t a 3D print be better?

Perhaps, but the logistical challenges with bringing 3D printers into classrooms and providing accompanying professional development are much more challenging then for example using videos or virtual manipulatives or computer models, which is why the current educational model is more focused on teachers using multimedia.

How did you use mobile makerspaces to stimulate learning? 

Mobile makerspaces are a great complement to having a room-based makerspace, and they are also a great way to jumpstart creation of a room-based makerspace if there isn’t one in a school already.

Do you think schools should have makerspaces?

I think schools should have a makerspace-mentality wherein every learning space is a potential opportunity for kids to learn by making cool stuff.

How can 3D printing help kids to become more interested in STEM?

3D printing is a great way to introduce kids to advanced design and engineering tools, and show them the rapid prototyping process.
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You’ve done research into music’s role in math education, how does that work?

Regarding music, I focus mostly on activities with musical instrument design, choreography-design, and music composition as contexts for mathematical problem-solving tasks.

Do you think that iterative experimentation with engineering and 3D printing will better prepare kids for the modern world?

Definitely, I think we should be teaching all students about the engineering design process just like we teach them about science and history.

How can we prepare kids for a world ten twenty years into the future when we don’t know what that world will be like?

One of the things we know won’t change is that productive people will always seek worthwhile projects, so I think the best thing we can do to prepare kids for the future is to help them have opportunties to learn where their talents and interests intersect with the problems and demands that the world will present.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

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Scientists Process Plant-based Resins Into Anti-Bacterial Filament

A group of researchers has just uncovered a means of creating anti-bacterial filament with anti-microbial properties. This filament consists of a variety of plant-based resin and metal nano oxide particles. It has the potential for developing all sorts of medical implements, bandages and tools that are also resistant to bacteria from the get-go. While bacteria […]

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Researchers 3D Print High Efficiency Batteries With Complex Geometries

Lithium-ion batteries are everywhere and in such common use. Since they are so ubiquitous, scientists have long been looking to improve their output. What they’ve found is that they have better capacity if their micro-scale electrodes have pores and channels. As a result, these structures allow lithium to transport through the battery efficiently. Now, scientists are looking […]

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