Peek behind the paper: 3D printing liquid crystal elastomers to mimic biological tissues

In this 'Peek behind the paper' interview, 3DMedNet and Christopher Yakacki, Mechanical Engineer Professor (University of Colorado Denver, CO, USA) take a closer look at the use of 3D-printed liquid crystal elastomers to mimic cartilage and other biological tissues.

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Christopher Yakacki and his team from University of Colorado Denver (CO, USA) have been the first to use 3D-printed liquid crystal elastomers (LCEs) - soft, elastic, multifunctional materials known for their ability to dissipate high levels of energy - to mimic biological tissues like cartilage, for example. 

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In this exclusive interview, 3DMedNet learns more from Yakacki about the use of digital light processing (DLP) for 3D printing LCEs, the translation of this technique into the clinic and the application of their prototype (pictured above) for spinal surgery. 

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Chris Yakacki: biography

My name is Christopher Yakacki and I am an Associated Professor in the Department of Mechanical Engineering at the University of Colorado Denver as well as the President and CEO of Impressio Inc. (CO, USA), a start-up spun out of the university to develop and commercialize liquid-crystal elastomers. My research has been focused on creating and developing active polymers, or in other words, polymers that have unique properties to perform a function. This could be actuating, changing their mechanical properties, enabling bone ingrowth or dissipating energy. Ultimately, my goals have been to use materials science innovations to improve human health. This can range from implantable biomedical devices to protective equipment, such as helmets.

Could you please tell us about the project covered in the recent 3DMedNet news piece, as well as any other related projects you may currently be working on?

In our most recent published study, we demonstrated how we can use DLP printing to create liquid-crystal elastomer lattices. Synthesizing and manufacturing LCEs has been a longstanding challenge in the field. It was not until recently that advances in photo-chemistries and click reactions have essentially unlocked the field to new methods of manufacturing. When I started researching these materials back in 2012, it was difficult to make a small, thin film of the material. Now we are able to use multiple methods of direct ink writing (DIW) and DLP printing to fabricate these materials extremely rapidly with exquisite control.

In our recent study, we were able to show that these materials can dissipate energy more effectively than traditional elastomers. ‘Elastomer’ is typically a fancy word for rubber, but when you think of elastomers and rubbers you think of materials that bounce and return energy when impacted. LCEs break away from this traditional mindset as they are rate dependent and absorb energy. This means if you were to compress the materials in your hand, it would feel soft and compliant, but upon impact it would stiffen up and absorb the shock. We have received funding from the NFL and PAC-12 conference to investigate these materials for use in football helmets.

How do you envision this material translating into the medical field?

Your body is full of soft, energy absorbing tissues, such as cartilage and the discs within your spine. Some key features of these materials are that they are soft, energy absorbing, and often times anisotropic (i.e. they behave differently when compressed or pulled in different directions). While that might sound like simple properties to replicate, it is extremely difficult to achieve with synthetic materials. Most polymers are either soft or energy absorbing, but rarely both at the same time. What we are trying to demonstrate is that LCEs are a new class of material that might solve this longstanding challenge. By utilizing 3D printing, we can design devices that are not only patient specific, but have anisotropic properties as well as allow for tissue integration.

What challenges have you faced with developing your material for 3D printing?

A few years ago I would have said the software to design lattice and optimized structures was difficult and hard to use. However, programs are evolving very rapidly and it has helped us in our research. Currently, we use nTopology’s (NY, USA) Platform software to create custom lattices.

What challenges with manipulating LCEs has 3D printing helped you to overcome?

Our group tries to ensure that 3D printing is adding value to the process and end product. We do not want to print for the sake of printing. DLP printing enables us to create these porous and lattice designs. In my opinion, there is no other practical method to achieve this, especially with the control over resolution and architecture. When we use DIW printing, it allows us to program anisotropy into the materials as we print. Again, there is no other practical method to achieve this. Overall, we are using 3D printing to achieve functional designs and material properties.

What challenges with designing synthetic materials for use with the spine could 3D printing LCEs help to overcome?

The spine is an incredible complex mechanical and biological system. When a person suffers from degenerative disc disease, it causes a lot of pain. Surgical procedures aim to relieve the pain; however, they do not always restore the natural motion or shock absorbing properties of the disc. Our approach is to explore the use of LCEs as a synthetic disc replacement – one that can mimic the function of a disc and restore a patient’s natural range of motion.

What’s next for you and your research?

We are going to keep developing these materials into real world applications. Liquid crystals have experienced great success in displays; however, LCEs have yet to have a commercial breakthrough. My belief is that they are well suited to address health related issues from concussions to tissue replacements.

Where do you see medical 3D printing in 5–10 years time? How could research such as yours affect this?

I hesitate to guess, only because the field is developing so rapidly. I would have said 3D printing LCEs was extremely difficult 4 years ago and now we can use multiple methods to create novel devices. My hope is that it we will be able to implant our first 3D-printed LCE device in that timeframe.

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Lead image: A DLP-printed LCE concept device of a spinal cage with a porous lattice architecture. University of Colorado Denver.

The opinions expressed in this feature are those of the interviewee and do not necessarily reflect the views of 3DMedNet or Future Science Group.

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