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Ruini Xiong and Crystal Zheng Talk Biodegradable Plastic Alternatives

By September 25, 2019October 6th, 2023No Comments

Crystal Zheng (left) and Ruini Xiong (second from left) are recent graduates of Templeton Secondary, where they participated in the school’s STEM program. In their last year of school, they partnered with Open Science Network to study silk fibre protein and shellfish chitosan, to determine how they could be manipulated to create a biodegradable plastic alternative. Their work achieved the top score at the Vancouver District Science Fair and won silver medals at the Regional Science Fair. We sat down with Ruini and Crystal to discuss the project, and their hopes for the future.  

It’s rare for students to get the opportunity to perform scientific research while still in high school. How did the two of you first get into it?

C: We first got interested in research when we joined the STEM program at Templeton Secondary. Through it, we heard about the Vancouver District Science Fair and were interested in participating, but didn’t know where to start. Our STEM teacher offered to put us in touch with a variety of possible mentors in Vancouver, and we wound up connecting with Scott Pownall from the Open Science Network (OSN). 

R: Open Science Network is a non-profit organization dedicated to promoting citizen science through a community laboratory that is open to members. They also promote science education to youth, and we were actually already familiar with them, since they hosted a STEM Mentoring Cafe at Templeton in November 2018. The STEM Mentoring Cafe, developed by OSN’s co-founder Wes Wong, was an event where they brought in STEM professionals from a number of fields to meet with the students and share their experiences. So we were very happy to work with Scott on developing a research project.

Once you were paired with Scott, wow did you decide on a research project?

R: Once we met up with Scott, he presented us with some ideas for research projects. One idea came from a 2011 TED talk by Dr. Fiorenzo Omenetto, a Professor of Biomedical Engineering at Tufts University. The talk was about the various uses of silk, including how it can be turned into a liquid and mixed with other compounds to be made into optical fibers, needles, nuts and bolts, and even tattoos.  

We were interested in tackling a local issue, so we decided to try and use silk to create a biodegradable alternative to plastic that could be used to replace straws for the upcoming Vancouver straw ban. It made sense, since plastic pollution and plastic waste is an issue that affects everyone.

From a molecular point of view, what is silk?

R: Silk is a natural fiber found in cocoons, consisting of two proteins: sericin and fibroin. The fibroin provides the structure, and the sericin acts like a glue. Our first step in creating a plastic alternative was to wash away the sericin using sodium carbonate, so that we could get at the fibroin. We then melted the fibroin down into a liquid using lithium bromide, and let it dry to form a film. 

C: We were also interested in mixing in other compounds to improve the material’s strength, and we settled on chitosan. Chitosan is a natural polymer obtained from the shells of shellfish. It’s used in tissue engineering as a scaffold because of its biocompatibility and wound-healing properties, and is also being researched for use in the food industry. But most importantly, we’ve found that it increases the strength of our silk samples. We’ve been working on figuring out the right ratio of silk to chitosan to produce the strongest film.

How do you test the tensile strength of the films?Fragile Silk Film

C: Unfortunately, we don’t have a machine to test the tensile strength of the films, so we have to determine the relative strengths of the different films qualitatively by pulling on them.

R: We tested their flexibility or plasticity by crumpling them to see if they would return to their original shape. We also put them into water and Pepsi, because our original goal was to use the material to create straws. In the end, we found that a 1:1 ratio of a 1% chitosan solution with silk produced the strongest, plastic-like film. It was the end product that we were aiming for. And although we were inspired to make straws, the flexible, plastic-like film that we developed could have many applications, for example as saran wrap for food packaging.

So you’ve come to the end of your project, and you’ve both graduated from high school. What are your plans for the future? Are you interested in pursuing a career in research?

R: We’re both now attending UBC for engineering. I’m interested in going into biomedical engineering, and Crystal is interested in biochemical engineering. I’ll think more about pursuing research further once I get more experience. One thing that this current project has made me realize though is that I want to combine science with business. I think that would be really interesting.

C: Agreed. We’re both interested in combining science and business. We recently worked on a project through an entrepreneur program for high school students run by undergraduates at the SFU Beedie School of Business, which was great! We want to find a balance between the two fields.

Do you have any advice for girls who are interested in pursuing a STEM field?

C: The most important advice I have is to be brave. Don’t listen to others when they tell you what you can or can’t do. If you’re interested in a specific area, go for it!

R: Definitely. Also, don’t be afraid to connect with other girls and try out new things together. When you get the chance to explore and find those passions, not much can stop you from pursuing it.


Thank you for taking the time to discuss your research project with us, Ruini and Crystal! We wish you the best of luck in your undergraduate studies!