Texas Tech University

Professor Wants to Solve 3D Biomedical Printing Problems

Amanda Bowman

August 30, 2018

Changxue Xu

Changxue Xu’s study will investigate why cells clump during the inkjet printing process, which could have a broad impact on the fabrication of 3D-printed artificial tissues and organs.

There are few things more frustrating than printing problems. Take it from the character Michael Bolton in “Office Space.” When a printer, or fax machine in his case, doesn't work the way it should, it leads to stress levels so high that pulverizing it to bits in the middle of a field with a baseball bat seems downright reasonable.

Destroying a company's property is wrong – and illegal – no matter how much the machine frustrates workers. However, Changxue Xu, an assistant professor in the Department of Industrial, Manufacturing & Systems Engineering (IMSE) within the Edward E. Whitacre Jr. College of Engineering at Texas Tech University, is working to ease that frustration when it comes to inkjet printing for 3D biomedical applications.

Picture of inkjet printing system in PI’s lab at TTU
Click to enlarge.

Xu's focus is on bioink, a unique ink used for 3D biomedical printing. Bioink contains two major components: biological materials and living cells.

“The problem with bioink is, it is considered cell suspension,” Xu said. “During the printing process, the cells will attach to each other to form aggregates. This cell aggregation and adhesion will significantly affect the printing process due to the cell interaction, then the printing process becomes very unstable.

“Each droplet formation process is different, and extra satellite, or secondary, droplets can form. During inkjet printing, there is a very complicated pressure wave, which drives the oscillating flow inside the nozzle. The motion is affected by the flow, and the cells can collide and adhere with each other. If the cell aggregations get large enough, then they can even block the nozzle of the printer.”

To study this phenomenon, Xu received a $318,000 grant from the National Science Foundation (NSF).

Schematic of inkjet printing of 3D vascular-like constructs
Click to enlarge.

“With this project, first we'll try to study the mechanism of cell adhesion and aggregation, then study how the cell aggregates affect satellite droplet formation,” he said. “Then, we can precisely control the printing process and further control the printing quality of the fabricated structure. We'll focus on the inside of the nozzle because it is glass, and we'll also use an imaging system to help us see the process more clearly.”

The printing quality for fabricated structures has an immense impact on the final product.

“The quality of the 3D structure is very important because if you can precisely control the droplet and the printing process, you will have a very good quality of fabricated structures,” Xu said. “If we fabricate a 3D structure, we need to incubate it. Then, the cells will proliferate and fuse together to form functional tissue and organ.”

One of the exciting things about Xu's study is it is crossing into new territory with this particular research.

“No one has done a specific study on how or why cells adhere with each other,” he said. “This is the beauty of this project.”

Microspheres showing encapsulated cells and cell aggregates
Click to enlarge.

Xu praised the IMSE department and Texas Tech for helping him facilitate the proposal process and guiding him as a newer faculty member.

“Texas Tech and the IMSE department provide excellent mentorship for me,” he said. “Bryan Norman, the IMSE department chairman, and the senior faculty help me a lot in terms of research proposals and teaching. They help me review my proposals and provide constructive comments. They also provide guidance on how to improve my teaching skills, how to handle plagiarism and other responsibilities of faculty.

“The university provides a lot of seminars and workshops to foster success for new faculty. It also invites program directors from agencies such as the NSF, the U.S. Department of Energy and the U.S. Department of Defense to help us build relationships.”

The research collaborations fostered at Texas Tech and the Texas Tech University Health Sciences Center (TTUHSC) also made an impression on Xu.

“I am so impressed by the intense research activities at Texas Tech,” Xu said. “For me in particular, TTUHSC has a very good medical school, which provides a lot of opportunities for collaboration. Chairman Norman emphasizes the research focus on engineering in medicine and strongly encourages interdisciplinary collaboration with the TTUHSC.

“The Dean's Office even helps set up a group involving the entire faculty from the College of Engineering and TTUHSC working on engineering in medicine so we can share news and use the network for internal collaborations.”