Radiopaque 3D printing

Our ‘radiopaque material’ paper has been published in 3D Printing and Additive Manufacturing journal (and here is the link). The X-ray of the hands was printed on a full page within the journal, just before the article. If that wasn’t enough for us, they used our work on the front cover for the December edition which is still sinking in months later!

December 2020 edition of 3D Printing and Additive Manufacturing journal cover showing our 3D printed hands

The term ‘radiopaque‘ describes a material that is visible under X-ray imaging. ‘Radiolucent’ describes a material that is invisible to X-rays.

Background

First, I will give some background as to why we developed this material.

In general, plastic-based 3D printing materials are not clearly radiopaque. This can cause issues if 3D printed anatomical models are being X-rayed/CT scanned or instruments are being used under X-ray/fluoroscopy.

The paper details how we created and 3D printed a plastic-based radiopaque material. This material shows up under regular X-ray imaging as well as CT imaging, and could potentially be visible using fluoroscopy and MRI, but have not checked these experimentally.

One point that I must make, is that radiopaque 3D printing is not totally new. Many papers have made anatomical models with FDM printers (that use thermoplastic filament) that have regions of varying radiopacity. However, the resolution for this technology is much less than that of resin-based 3D printers. Smallest features can be as large as 1mm compared to 0.1mm for some resin-based printers. And since resin-based 3D printers have higher resolution, they generally come with more limitations than FDM printers, making high-quality radiopaque multi-material 3D printing difficult. Some research groups are adding radiopaque material to PolyJet 3D printed parts after printing, however, the quality does not compare to printing with radiopaque resin.

For this project, we used a Connex 500 multi-material 3D printer (I have described this in an earlier blog post here) so that radiopaque material could be printed within non-radiopaque materials. This “multi-material” feature was perfect to demonstrate the new material. The base material for this project was MED610, a clear, biocompatible material. The second was TangoBlackPlus, which is a black, rubber-like material. We added radiopaque powder to MED610 in order to create the radiopaque ink.

MaterialDescription
MED610Clear, biocompatible material Rigid when cured
TangoBlackPlusSoft, black material Rubber-like when cured
Radiopaque materialWhite, rigid material when cured. Visible under X-ray.

Proof of concept

As a proof of concept experiment for this radiopaque ink, we 3D printed a hand with radiopaque bone. We could have selected any feature for this, but our Connex 3D printer came with a hand/bone demo model so we decided to make use of this. TangoBlackPlus was used for the soft tissue and the radiopaque material represented bone. These 3D printers are not made for custom material so we had to trick the 3D printer that it was actually printing commercially available material (which could actually invalidate the 3D printer warranty). Since TangoBlackPlus is visually opaque, the bones could only be seen under X-ray, forming an ideal proof-of-concept experiment:

Above: X-ray of the two hands, one with radiopaque bone and the other with MED610 bone.
Below: Photograph of the two hands. The hands are completely indistinguishable in the photograph but clearly different under X-ray.

Limitations

This project was overall successful in 3D printing radiopaque material but there were also some limitations. The temperature of the print head accelerates the powder settling out of suspension. The hand took four hours to print and so settling was not a major issue. As well as settling, the powder did block up the print heads slightly which caused some uneven layers. We developed a cleaning method to restore it after each ‘experimental print’ . Overall, this proof-of-concept experiment was successful and the material now needs to be further developed to reduce these limitations.

Applications

A radiopaque 3D printable material has potential applications in a wide variety of industries, including med-tech, aerospace, automotive and general manufacturing. Since our research group focuses on medical devices, I will go into greater detail on the medical applications for this material.

  1. Anatomical models: More realistic anatomical models can be produced, which would be very similar to the patient’s original body part under X-ray. This can be used to practice procedures on a patient-specific model or even teach medical students how to perform procedures under X-ray imaging such as fluoroscopy.
  2. Calibration for medical imaging: Any medical imaging technique that makes use of X-rays also causes potentially harmful radiation to interact with the patient’s body. New imaging equipment, for example a CT machine, could make use of anatomically-accurate phantoms for calibration, as well as testing new machine features. This would prevent any unnecessary radiation exposure to patients. A 3D printed limb or torso with controlled radiopacity could be used for daily calibration on existing machines.
  3. Medical training: Rare cases, such as complex injuries, could be 3D printed and used for diagnostic and therapeutic exercises for medical students. Standardised phantoms could be used to train radiologists to make diagnoses from X-ray or CT imaging.
  4. Better visibility of plastic-based devices within the body: Currently, instruments/implants that do not show up under X-ray have marker bands added so they are visible. Polymer/plastic-based medical devices, such as catheters, could be 3D printed in a single pieces including a radiopaque marker band which could allow easier manufacturing of these devices since the part is made in a single step.

Visuals

I have linked two YouTube videos here that are useful for better visualising this exciting technology.

The first is a full-scale CT reconstruction of the hand and the control hand (with MED610 bones).

The second video shows a microCT reconstruction of the experimental hand only. This video has a smaller field of view and so the thumb did not fit within the area being scanned. The microCT shows greater details such as the streaky layers that have already been mentioned as part of the limitations.

Working from home: Week 9

For the past nine weeks I have been working from home – something I never thought would happen during my PhD. I have been quite busy since the last blog post and this is definitely the longest blog post so far.

Working Remotely

There are definite perks of working from home. I am enjoying being able to wear comfy clothes all day, not that I ever put much effort into my outfits anyway. And it is nice to be able to wake up ten minutes before I intend on starting the day. The mornings are more relaxed as I can have breakfast while checking my to-do list and emails. I have spent some sunny mornings working outside as well, which is not as productive as working at a normal desk, unfortunately, but is a nice change of scenery.

Outdoor desk for sunny mornings

In addition to this, I was a teaching assistant for a module this semester and I was scheduled to teach eight tutorials for this. I had only delivered three tutorials by the time that UL closed, so I had to record the remaining five at home. This actually took less time than it would have to deliver these in person. Since I usually pause to give student a chance to take down solutions in class the tutorials last for 50 mins on average. Recording tutorials at home took less time as I could talk through without pausing. Students could then rewind to parts that they were struggling to grasp. In addition to this, I only had to record my tutorial once instead of delivering the 50-minute tutorial five times a week.

Don’t get me wrong, there are definite drawbacks to this situation as well. It is difficult to stay as focused as I would be in my usual office space. I have found it difficult to be at my desk by 9 and I am taking more tea/coffee breaks than I would at work, mainly because it is so convenient. I have been meeting most of my goals during the lockdown, however all too often I feel that I have not been productive enough, and find myself working a few hours over the weekend to make up time. This is something I am trying to avoid, though. I really have got used to my diary and this does help me to keep focused and complete the key tasks each week. Working at home while my partner and other housemates are in the house was always going to be less productive than a quiet office space. I’m sure this is something everyone has to deal with, not to mention sharing laptops and desk space.

PhD progress

There has been a lot of different areas of progress for the PhD in the last two months. Firstly, in April the IRC, who are funding my research, approved my first year progress report so I am now officially in the second year of my PhD.

Possibly as exciting, the first paper that I have written has been accepted to a major 3D printing journal, with minor changes. I will do a blog about this paper when it is finally published.

Last month I also submitted an abstract to a conference. This conference is due to take place in July, but I cannot see this actually going ahead. I am expecting this to be postponed. I likely will attend the conference whether I am chosen to speak at it or not.

Also last month, my research group (Design factors) held update presentations for all the PhD students. I presented my work and received good feedback. This presentation took place during 65 Roses week and I used my last 30 seconds to promote this event. Many researchers actually did donate to the cause.

Taught modules

This semester I took two modules; ‘Writing Science and Engineering’ and ‘Immunology and Microbiology’. I was due to take exams in both subjects during May. Obviously, these exams could not go ahead as scheduled. Instead, both lecturers decided to give assignments and quizzes to make up the marks. I am more used to sitting exams rather than end of term assignments but I actually preferred doing assignments. There was more time to answer the questions, meaning more time to think, less stress and less cramming. I do feel that assignments are more practical than sitting exams. It really tests how a student would solve a problem in real life, rather than learning off pieces to regurgitate in an exam.

COVID-19

One thing I did not expect at the beginning of lockdown was that I would be returning to the campus before the lockdown had been lifted.

Mid-April I was asked if I would help some of my colleagues with 3D printing, cleaning and assembling parts for the Rapid Innovation Unit (RIU). I was given permission to access the campus by the Dean of Science & Engineering and the President of UL. RIU was set up this year to create solutions for problems in the local hospital, University Hospital Limerick. The first month since RIU was set up was mainly focused on developing solutions for the COVID-19 crisis such as PPE and adapters, as outline in this video. The video currently has almost 40k views, which is impressive since RIU was first set up in March. You can follow RIU on twitter under the handle @RIU_UL for updates.

Skype a scientist

At the beginning of lockdown I thought I could be quite bored without lab work and signed up for ‘Skype-A-Scientist’. This is a website that pairs teachers and their class with scientists and they can have a chat about science. In the first month I was matched with 12 teachers, which I was a little overwhelmed by. I had organised two calls, with classes in North Dakota and Virginia. Neither call went to plan. During the first call my presentation froze and we just had a discussion about 3D printing. I was completely unable to connect to the second call and after 30 mins we decided to leave it. I recorded the presentation instead and emailed it to the class.

I blame my laptop for these issues, but I don’t think I will sign up for any more skype calls. I had contact with some of the other teachers that I had been matched with but I don’t think teachers want to do skype calls until the classrooms are back to normal.

Overall, I have has a busy few weeks since the campus closed. I am missing my colleagues, lab space and frustrated I cannot continue with important testing, but the closure is completely necessary to keep everyone safe. I had been uploading blog posts monthly, but I feel that uploading once every two months from now on might make for more interesting posts.

September Blog: My busiest month since starting my PhD

Writing these blogs is a catch-22. The more time I have to write the blogs, the less I have to write about. When I have loads of updates and events to write blogs on, I barely get a chance to sit at my desk to write them. This was definitely the case during the month of September as I have been so busy and am only getting around to writing the September blog now.

Since my last blog at the end of August, I have started studying a new module, teaching tutorials/labs as a teaching assistant, attended a 3D printing workshop, travelled to a manufacture exhibition, I did a school visit and set up an Instagram page for our 3D printer. September has definitely been my busiest month since starting the PhD!

I will start with the college-related updates. As I am doing a structured PhD I am required to study and pass exams for two taught modules (at least two, and more if I want to). This semester I am taking ‘General Microbiology’. I haven’t studied biology since the Leaving Cert and at that, we only spent one week studying microbiology. I am actually enjoying the module more than I anticipated. The lecturer does his best to make the classes interesting (which I imagine is difficult with 200+ students in the lecture) and the labs seem easy so far with a focus on understanding core concepts. I think this is important as many students (including myself during my undergrad) don’t understand ‘the basics’ of modules they take in college, even though they can pass the exam.

As part of my contract, I can teach up to six hours a week. This semester I am assisting with the materials half of a product design module. I sit in on the classes and give thoughts on student’s assignments that were assigned the previous week. As part of this I am delivering two lectures; one on ‘environmentally-friendly alternatives to plastics’ and a second on ‘Additive manufacturing/3D Printing’. I have been preparing the presentations for these and my lectures will be delivered in the next two weeks. I have been collecting samples from different 3D printing technologies this month to pass around the class as I talk through the different types.

Tensile samples printed on an Ultimaker FDM 3D printer

I really feel that I have been away from the office for the majority of September. I attended a ‘Point Of Care 3D printing’ in St. Thomas’ Hospital London. This event was sponsored by Materialise. I flew from Shannon to London the night before, stayed in a hotel and flew home again straight after the conference. I met some very interesting people at this event, some were in early stages of their career, like me. It was nice to chat to people in the same boat as me at a conference as I have felt much younger/much more inexperienced than others that I have chatted to at conferences in the past.

A few months ago, a science/physics teacher that I am friends with asked me to visit her school and talk to some of the students about 3D printing and what I do. I feel that the visit went really well, with loads of interesting questions from the class. I was actually surprised at the level the questions were at – it showed that they had understood majority of what I had been talking about and were genuinely interested in the technology. I hope they enjoyed the visit as much as I did.

Last week I attended the TCT show 2019 (Design-to-Manufacture Innovation). This exhibition was not just for 3D printing but Majority of people there were demonstrating their 3D printers, new 3D printing materials as well as launching brand new 3D printers. For this event, I travelled over to Birmingham and back in the same day. This is really only possible because the event is in the NEC, which is a two minute train from Birmingham airport. I flew back to Dublin and stayed in Dublin as I had three training days in the National Children’s Research Centre (NCRC, Crumlin) directly after this trip.

The NCRC part-fund my PhD, along with the Irish Research Council. My PhD mentor is the Research and Operational manager for the NCRC. She organised these training days for me and the other students that receive funding from the NCRC. As part of the training we covered grant writing, GDPR, health research regulations (HRRs), lay abstract writing, biosample storage, media training and good clinical practice training. I have mentioned this in previous blogs, but I really think now is the best time to get these training sessions done as I am just beginning my research project and these skills will be so important. I got to meet the other students who all had completely different PhD projects to mine. This was a great networking opportunity as well as being able to compare what is different in each of our universities. The others were from UCD, Trinity, NUIG and RCSI.

As well as everything else, this month I have also set up an Instagram account for our 3D printer/ my PhD project. We decided to name the printer Grey, so the Instagram account is simply named ‘Greys3DPrinting‘. I find the best way to explain the technologies are with time-lapses of parts being printed. As well, 3D printed models are so easy to understand when you can hold them and look at them from a range of angles. For this exact reason, I think it is worth setting up an Instagram account to upload relevant photos and videos of my project to. I will document interesting prints here (as well as trips to conferences and events) in real time but I will continue to write a blog once every month or so.

Introduction

First, a little bit of background on how I got to where I am..

I have been studying in UL for the past 6 years. I began my undergrad in Applied Physics in September 2013. I graduated in May 2017 and went straight into a taught masters (Biomedical Device Materials).

My favourite elements of both my undergrad and Masters were the research projects (both materials related – one was on printing a material for orthopaedics that would stimulate bone growth once grafted, the second was developing a material that bacteria could not adhere to). I enjoyed beginning a new project, immersing myself in all of this new information and slowly becoming familiar with this new area of science. I enjoyed the lab element also – running a multitude of tests and again, building up the knowledge of this relatively new field. It was quite satisfying to have built up a project and compile all of the project background, experimental data, results and conclusions in one neat document. This feeling of satisfaction and accomplishment is why I decided to pursue a PhD in material science. I am excited to start a new project, immerse myself in it fully and eventually become an expert in this field.

As I was coming to the end of the Masters I decided I would like to remain in research and I began looking for possible projects. During the material science masters I had done an assignment on an area of my own choice. I chose to write about ‘3D Printing in Medicine’. As part of this assignment, I learned the variety of areas that 3D printing can be used. I was surprised at the range of areas that 3D printing was already being applied to in medicine, such as anatomical models for planning surgeries, explaining procedures to patients, educating medical students, prototypes for medical devices, small medical devices, and of course, prosthesis.

I had decided that this (relatively) new and exciting area that I was now fascinated by was the area I wanted to study. I was shocked to find out that there was a research group in UL that had a multi-material 3D printer (it can place 2 materials at the same time, building components within other components). As a long shot, I emailed the head of the research group and asked if he had any material science related projects that I could get involved with. To my disbelief, he scheduled a meeting with me for the following week. I met up with the head of the research group and a second member of the group. I was given a tour of the lab and shown the printer and a variety of printed components – extremely exciting stuff! They had a project that they thought I would be a good fit for – suspending additives in the liquid 3D printing resin to change the properties of the final components. The property they were trying to enhance was radiopacity (making the component show up on x-rays, wheres the ordinary ink does not). I also felt that I was a good fit for this, given my background in physics and material science (along with my new found love for 3D printing). I was offered a research position working on this project for the summer. Needless to say, I accepted!

At the end of the summer, it was decided that we would apply for PhD funding for me to continue working with 3D printing and with the same research group (https://designfactors.ie/), but in a slightly different area. This time, instead of enhancing the radiopaque properties on the 3D printing ink, I would be making the printed components antimicrobial. Specifically, these antimicrobial components would be small accessories for PEG feeding tubes, specifically for children with Cystic Fibrosis. PEG tubes are supposed to be a short-term feeding solution, but often are left longer than this (if the child is too sick to go for surgery to replace the tube). This long-term use can result in degradation which leads to leaks/cracks in the PEG line. PEG feeding tubes are basically ideal incubators for micro-organisms (37 degrees Celsius, humid conditions) and are outside of the reach of the patient’s immune system, which increases risk of infection (which poses an extreme risk for patients with Cystic Fibrosis). The idea of a repair accessory/ device which is inherently anti-microbial was crafted to combat these two issues with PEG tubes.

I applied for funding from the Irish Research Council (under the Irish Research Council Enterprise Partnership Scheme) and this application was successful! Our enterprise partner is the National Children’s Research Centre – who have a high quality Cystic Fibrosis research team and have ongoing research in infection and immunity. I look forward to working alongside this partner.

So, we have been working on the radiopacity project since June (my summer internship was extended to Christmas, and then until the end of February). My PhD official start date was 1st March 2019, and I am now in between wrapping up the radiopacity project (hopefully publishing a paper on the key findings shortly) and kicking off the PhD project!