The University of Southampton

Author: Alexander Long

From 3D Printing to Bioprinting – Is This the Way Forward?

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The concept of 3D printing in general is fascinating to me, especially the idea that designs, both creative or functional, can be produced from computer modelling. I have experience with using such printers (both before and during university), and was intrigued when I found out through the lectures that they can be used in combination with stem cells; other examples of its medical applications are producing custom-tailored prosthetics and printing of tissues. As someone who has only printed using plastics, this topic appealed to me.

What is Bioprinting?

Bioprinting is a process very similar to typical 3D printing using plastic or metal, albeit replacing such materials with desired cell types mixed into a gel (e.g. gelatine) to create what is known as bioink. The mixture is then printed layer-by-layer until the desired structure has been produced. There are three main strategies for bioprinting:

  • Inkjet – heat or ultrasound is used to produce pressure to force material from the extruder
  • Microextrusion – mechanical means of releasing material
  • Laser-assisted – releases cells via the pressure generated by a laser on an absorbing layer

Bioprinting has promise in its applications for printing tissues and organs, such as ears for those suffering from microtia, through printing their cells into a replacement ear. This reduces the need for patients to undergo more invasive surgery.

Examples of the three main types of bioprinters. https://www.nature.com/articles/nbt.2958

Other Applications of 3D Printing

Another way in which 3D printing can benefit patients is through indirect means; through creating accurately scaled replicas of organs undergoing surgery, such as hearts, surgeons can plan the surgery ahead of operating. The video below documents how Lucas Ciulean, a child born with an uncommon heart abnormality, was able to recover after surgery in which a replica 3D printed version of his heart was studied ahead of time. When I first watched it, I found it thought-provoking that the technology I had been using for years was capable of providing such valuable insights to patients with atypical conditions. I also believe this video raised an important point regarding minors undergoing surgery; by allowing parents to visualise the surgery planned for their child, these replicas can provide the parents with some comfort and reassurance. In my opinion, this is of the utmost importance since patients, or patients’ guardians, should feel informed and comfortable about any planned procedures.

Another interesting application of 3D printing has been displayed by MIT engineers, in which a prosthetic heart has been produced from soft plastic. The process started similar to the previous example, by taking scans of the patient’s heart and reproducing a 3D model from them; however, it deviates from the prior example since the model is then printed in a softer, flexible plastic. By fitting sleeves around the heart replica, it can mimic the rhythmic pumping of an actual heart through a pneumatic system. This is an interesting contrast to the idea of bioprinting a heart, although I have concerns regarding its viability due to the need for attachment to a pumping mechanism which may impact the patient’s comfort.

My Final Thoughts

The technique of 3D printing has been an interest of mine for years, and expanding this knowledge to the applications discussed above has been a rewarding journey. The current research state of bioprinters is really impressive and by building on the current knowledge, this technology will hopefully become more widely available to aid patients in need. I think that research should continue to innovate in both classical plastic printing, as well as in bioprinting to provide patients with more choices, and a greater level of reassurance and control that the option chosen is best for them.

Cochlear Implants: Tuning and Technology Advancements

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Hearing is a sense that I, and likely many others worldwide, take for granted. That said, around 1 in every 6 adults in the UK live with at least partial hearing loss. The technology behind cochlear implants piqued my interest after listening to the insights from users in the lecture, leading me to begin reading parts of Dr Yoder’s cochlear implant journey.

What is a Cochlear Implant?

Cochlear implants are made up of both internal and external parts and require a relatively short surgery to fit. The external parts are made up of a microphone to pick up the sound waves, a language processor to convert the sound waves into electrical signals, and a transmitter to transfer these to the internal components. The language processor and microphone usually rest on the ear, while the transmitter is placed further back on the head. The transmitter is held on via a magnet fitted under the skin during surgery. This allows for the previously converted electrical signals to reach the string of electrodes inserted into the cochlear, which stimulates the auditory nerve directly.

Cochlear implants aid the users’ hearing through a string of electrodes inserted into the cochlea. https://brsh.org/cochlear-implants/

Tuning

One aspect of cochlear implants that I found fascinating was tuning and the period over which it takes place; initial tuning usually takes place one month after the surgery, with periodic sessions after this to slowly ease users into the new sounds. This initially shocked me; “Why does this process take so long?”, I found myself thinking. However, after reading Dr Yoder’s experience with tuning as well as others (seen in the video below), I realised that hearing is not restored with the surgery, but with the practice users do to re-understand how everyday noises and speech sounds. The video below by Cochlear Americas documents four users and their experiences with training themselves to understand how to hear through their new implants, which I found very insightful.

Current and Future Research

A recent publication in Ear and Hearing in 2023 discussed advancements in tuning of cochlear implants, and how artificial intelligence can be used to outperform traditional tuning methods. The traditional method, despite performing less effectively, was preferred by participants, owing to it feeling more comfortable for them. I believe that this aspect of optimising implants should not be neglected; how the users think or feel about such methods, be it tuning or any other aspect of the implants, is of utmost importance.

A less recent article from the engineering department in Cambridge highlights how 3D printing can be utilised to improve cochlear implants. The fluids inside the cochlear ducts are highly conductive to electrical signals and implant users often, due to this conductivity, experience distorted sounds through their implants; this is known as current spread. The use of 3D-printed cochleae, paired with machine learning, allowed researchers to analyse and predict how current spread was impacted by the cochlea’s shape and conductivity. Dr Shery Huang, an associate professor in Bioengineering at Cambridge, suggested that this is an extremely useful application of 3D printing since data regarding patients must be kept private; Dr Huang was quoted in the article, stating that to solve this, “3D printing is a powerful tool to create physical models which might provide a well-characterised training dataset as a purpose-built surrogate to clinical data for machine learning”.

Bioelectronic Prosthetic Advancements

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An article posted by William A. Haseltine to Forbes shares recent insights into breakthroughs in prosthetic brain-machine interfaces. brain-machine interfaces are not entirely new technologies, however, the Ortiz-Catalan hand discussed in this article varies in a few ways from previous prosthetics. The article states that one major complaint from prosthetics users how comfortable it is during use; the Ortiz-Catalan hand aims to address this through attaching the prosthetic directly to the skeletal system via osseointegration.