Rethinking Bioprinting for Sustainable Bioelectronics

blank blank Feb 10, 2022

Bioprinting has been a promising additive manufacturing technology that has proven its competency for biomaterials, cells, tissues, and human organs. Through manipulation of pre-, post-printing processes, bioprinting has been able to find wide applications in drug development, fabrication of organs, tissue engineering, wound management, treatment, etc. However, these are the fields that traditionally fit into the application area of bioprinting.

Evolving needs and customer-centric solutions have put a demand on creating new biomedical devices. This has also highlighted the need for new manufacturing ways that are compatible with new forms factors, designs, and materials. So far bioprinting has caused the excitement for organ printing, but we have somehow overlooked its potential for other fields. The use of bioprinting methods may extend far and wide beyond what it is currently used for. 

Bioelectronics is an area that encompasses electronic devices that find application in the healthcare and biomedical sector. This is an exciting field, which lies at the interdisciplinary boundaries of electronic engineering, biology, and manufacturing. Research at the intersection of such fields has the potential to become a pillar of medical treatment and play a key role in the future of MedTech innovation. Bioelectronic devices are manufactured using traditional electronic technologies. Although these technologies are reliable and have been standardized, they use high-temperature and vacuum processing that is not compatible with new emerging materials.

Our research group at Aarhus University, Denmark has been working extensively in the area of bioelectronics trying to combine biology with electronics in new ways through the bioprinting route. We are looking to go beyond the traditional roles of bioprinting, i.e. to replace damaged tissues and organs. We believe that bioprinting is a powerful tool that can contribute to building the next generation of bioelectronic devices. By pushing the boundaries of the biomedical field. We have created new-age devices for wound management, muscle atrophy, and health monitoring well-suited for fabricating skin-compatible and soft devices.  

Quest for new biodegradable and biocompatible materials

Electronics have made a tremendous impact on human society, and this has also led to issues of electronic waste pilling on earth, just like plastic. This has led to research efforts in the direction of creating new electronic materials that are biodegradable. When it comes to biomedical devices, there is an additional need for the devices to be biocompatible and have transient nature. There are various scenarios in healthcare where electronics need to operate for a limited time and then degrade generating biologically safe products. Our research group is focused on creating a library of novel materials that are environmentally safe and have good electronic properties. We have started work on piezoresistive, piezoelectric, and conducting materials that are prepared using green chemistries, and possess different water dissolution rates. The as-synthesized materials are then converted into printable inks to create devices with a specific thickness. The focus is more on polymer materials due to their biodegradability and ease of processing. We have developed a printable piezoelectric material based on polyvinylidene difluoride (PVDF) that shows remarkable properties to make sensitive sensors. The material can be partially degraded but uses non-toxic reagents. The natural extension of this project was to work on a fully biodegradable piezoelectric material. This poly-L-lactic acid (PLLA) based material can have tunable properties of amorphous nature and crystallinity, thus giving it a unique spin for various applications. In another project, we have taken inspiration from mussels and created polyvinyl alcohol (PVA) and dopamine composite to have not just biodegradable properties but good adhesive qualities as well.

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Figure 2: Images of different polymer films synthesized at PET lab: Poly-L-lactic acid (PLLA) and Polyvinyl alcohol (PVA).

Next-generation bioelectronics

Working with new materials requires new fabrication methods to make devices. We are exploring several different bioprinting methods namely 2D, 3D, inkjet-, laser- and extrusion- to print next-generation bioelectronics devices. Leveraging the attractive features of bioprinting with traditional techniques allows us to create new-form factors with complete integration for soft devices.  

Figure 3 shows some of the printed devices fabricated at PET lab. pH patch sensor used bioprinting to print a multilayered architecture to monitor the pH levels in the wound extrude and also the hydration around the wound site. A flexible pressure sensor was created on eco flex via inkjet printing. The printed ink and the substrate can also be stretched without losing functionality. The electrostimulation patch was an interesting study, wherein room-temperature metal ink was printed and sandwiched between printed hydrogel layers. The fully printed patch did not require any post-processing or sintering to functionalize the materials. The patch was stable in bio-medium for several dates and no ink leakage was observed. The patch was tested for biocompatibility using C2C12 and fibroblast cells. All these patches are partially biodegradable. To move towards bioresorbable electronics, which degrades completely inside the human body environment, we printed an antenna circuit on a melt-drawn Polycaprolactone (PLC) biodegradable polymer coated with a hydrogel. Our current research, thus, is directed towards creating conformal, flexible, and biocompatible devices for future medical applications through the printing route.

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Figure 3: different bioelectronic sensors and patches created using biodegradable and biocompatible materials. 

Research Goals

Forward progress will require contributions from a multidisciplinary team. Our research group is composed of electronics engineering, material scientists, chemistry, and biomedical experts. What is also unique about our group is that we research fundamental science pertaining to materials but also have projects higher on technology readiness level (TRL) with industry partners. Through understanding the science behind bioprinting, we are hopeful to create impactful work for the healthcare and biomedical sector. 

About the Author:

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Shweta Agarwala is a tenure-track assistant professor at Electrical and Computer Engineering, Aarhus University. Her vision is to enable component and wire-free electronic circuits that are flexible, bendable, conformable, and biodegradable. She is achieving this through material innovation and the 3D printing routes by printing electronics on unconventional substrates for next-generation electronics especially catering to the healthcare and biomedical sector. Shweta is the author of more than 40 peer-reviewed papers published in internationally renowned journals, books, and conferences. She is the vice-chair for the Women in Engineering chapter in IEEE Denmark section and an enthusiast STEM advocate. 

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