Researchers Kick 3D Printing Trend up a Notch With Self-charging Medical Wearable

November 12, 2021 by Kristijan Nelkovski

With advancements in materials science and electronic engineering, 3D printing is entering the stage of developing made-to-fit wearable electronic systems like that from the University of Arizona.

Just a decade ago, additive manufacturing was nothing more than a very expensive process used to prototype components for large manufacturing corporations. 

Now, because of readily available and inexpensive electronics combined with online communities that share their knowledge and experience of microcontrollers, coding, and robotics, 3D printing has become more readily available. This availability is not just to new individuals entering the engineering field but also to research institutes, universities, and companies that would have otherwise not been able to afford this type of technology. 


A graph showing the potential growth of 3D printing for medical devices.

A graph showing the potential growth of 3D printing for medical devices. Image used courtesy of Prof Share


One area that is starting to reap the benefits of 3D printing is the medical industry. Today, this article will dive into the medical uses of integrating 3D printing technologies with electronic systems, as well as two recent research projects where engineers have developed flexible 3D printed wearables for use in the medical field.


3D Printing Medical Wearables

Even though this technology is still in development, engineers have created 3D printed circuit boards and even electronic components combining different types of materials (conductive and non-conductive) within one 3D printed structure. 

Unlike the traditional PCB manufacturing processes, this method would allow electronic devices to be printed in any three-dimensional shape, complete with an outer shell and interior components.

One of the more unique applications for this technology is for manufacturing wearables used in the medical field. By being able to 3D print electronics into any shape, engineers and medical professionals can develop personalized electronic devices specific to a patient or user's body and needs. 

Currently, these wearable devices aren't fully 3D printable since some technology elements such as the 3D printed electronic components are still experimental and aren't nearly as efficient, robust, and, most importantly, small as their microelectronic counterparts. 

Some companies, such as many hearing aid providers, are already using this technology to develop only the patient-specific housings regarding empty spaces for embedding a ready-made electronic device. In contrast, others are going all the way by printing out the whole housing, circuit, and some sensors of their device as one single object, this time with regard for empty spaces only for the electronic components instead of a pre-assembled circuit.

Hoping to keep the momentum and growth of using 3D printing in wearables, specifically in the medical field, so a low-cost solution from Harvard.


Past 3D Printing Device Paves Future Trend 

In 2017, a multidisciplinary team from the School of Engineering and Applied Sciences (SEAS) and Wyss Institutes at Harvard, led by biomedical engineer and M. D. candidate Alexander D. Valentine, developed a low-cost hybrid 3D printed wearable integrating soft 3D filaments (conductive and non-conductive) with rigid electronic components into one flexible device.


The researcher's prototype. Image used courtesy of Valentine et al and Harvard University


The material they used is called thermoplastic polyurethane or TPU for short. The advantage of TPU is that it is bendable and can also be enriched with metals, in this case, silver flakes, to make it conductive and used for printing anything from a device's electrodes to even capacitive sensors. 

The flexible property of TPU enabled the Harvard team to make their circuits and sensors flexible while also using it as a glue to keep their non-flexible components in place. 

According to the team, one of their test prints, consisting of 12 LEDs placed on a 3D printed silver TPU circuit, was repeatedly bent and stretched without reducing light intensity and any mechanical failures. 

Recently, the Harvard team developed two wearables by printing specific structures alternating between conductive and non-conductive TPU, one featuring a strain sensor and one featuring a pressure sensor. These sensors were fully 3D printed as one wearable device where LEDs, resistors, and a microcontroller were the only non-printed components placed during the printing process.

These developments are just one step in the right direction for making 3D medical wearables a more cost-effective option to standard PCB manufacturing. A more recent advancement in the research field concerning 3D printing wearables claims never to need a charge. 


3D Printed Wearable That Never Needs to Charge

The most recent research into 3D printed wearable technology was published earlier this month by a University of Arizona team of electronic and biomedical engineers led by professor Philipp Gutruf and faculty fellow Craig M. Berge. The team developed a wirelessly powered "bio-symbiotic device" that can be custom 3D printed based on scans of its potential user, which uses TPU technology.


Example of the team's bio-symbiotic device. Image used courtesy of Gutruf and the University of Arizona

This wearable claims to be lightweight and breathable as it's printed in a mesh-like structure, making it easy for users to wear it under their clothes without noticing it or being bothered by a bulky device. 

The idea is to allow for wearables to be custom printed for any part of the body where a sensor placement is necessary for gathering data without causing discomfort to its user.

The team behind this device achieved a 24/7 'on' time by combining compact energy storage and wireless energy harvesting replacing batteries with a power transmitter capable of powering the device within a range of a couple of meters. The energy storage unit can also power the device for a short period, even when it goes out of the range of the system.


Block diagram of University of Arizona researchers device. Image used courtesy of Gutruf et al


According to Gutruf, the device is designed to have no interaction with the wearer. The wearer only has to place the device on their body, and afterward, they shouldn't notice it as it does its job. 

Similar to the technology of Harvard's 3D printed wearables, these devices use a combination of printing some elements of the device and embedding electronic components during the printing process. The result is a fully flexible mesh band that can go over the body part it's designed for.


The Future of 3D Printed Wearable Technology

Only in the past couple of years have additive manufacturing technologies advanced enough for their use to go beyond the prototyping phase. The advancements of many teams of engineers working in different fields have allowed 3D printers to be used for building systems layer by layer, from embedded electronic devices such as these wearables to structurally sound 3D printed buildings.

Despite the technology's many challenges, each new innovation in materials science furthers the scope of the parts and functionalities that designers can embed into a device within a 3D printing process. 

With readily available and affordable components and materials, this technology has the potential to find its way to a broad audience of users, especially if it is as durable and resistant to failure as its engineers claim. It will be interesting to see how the world of 3D printing keeps innovating and finding new ways to create better devices.