After a day of volunteering at COSI Columbus, Elli Tai would return home to Hilliard and talk about how she led experiments involving liquid nitrogen, electricity and more.

The stories piqued the interest of her younger brother, Daniel, who soon followed in her footsteps.

The siblings have spent the past three years volunteering together at COSI – a team effort that will end this summer when Elli, who recently graduated from Hilliard Darby High School, heads to the University of Texas in the fall to study actuarial science.

"It's still a fun thing, especially knowing she's going off to college," said Daniel, 15, a junior-to-be at Darby. "I have to savor these moments while I can."

Elli, who long has had a passion for science, began volunteering at the science center five years ago, at age 12 – the earliest age at which a person can volunteer at COSI.

"I always loved going to COSI as a kid, so when I heard you could volunteer there, I was like, 'Yes!' " said Elli, now 17. "It's pretty awesome getting to inspire the next generation of scientists."

Since 2015, she and her brother have volunteered up to eight hours on weekends during the school year, expanding that commitment to as many as 24 hours during the summer break.

"My favorite part about it is seeing the look on kids' faces when they realize something for the first time," Elli said. "They turn around like: 'Whoa, I didn't know that was possible.' "

COSI relies on the Tai siblings and about 500 other active volunteers – including 300 youth volunteers – to create "a more personal experience for our guests," said Terri Gregoroff, director of volunteer services.

The youth volunteers, Gregoroff said, often serve as role models for the many younger children who visit COSI.

Some volunteers lead the hands-on demonstrations, covering subjects such as astronomy, biology and physics; others might work in guest relations, answering visitor questions.

New volunteers are paired with seasoned volunteers as they learn the ropes, Gregoroff said. As newcomers gain experience, they can take on more responsibilities.

"Showrunners" such as the Tais might lead basic demonstrations (such as building an arch from foam blocks) or more advanced demos (such as working with liquid nitrogen).

By now, Elli and Daniel have proved capable of handling the more complex shows, including rat basketball (which is exactly what it sounds like) and the electrostatic generator. Elli also operates the high-wire unicycle ridden by guests.

"Even from the beginning, she demonstrated maturity," Gregoroff said of Elli. "She is so intelligent and bright and has excitement about the science and sharing that for others."

Sarina Tai, Elli's mother, sees that same enthusiasm in her daughter.

"She wholeheartedly enjoys her time there," said Sarina Tai, a pharmacist, "and it has given her a great sense of pride and confidence."

Now, as an experienced team member, Elli mostly helps to train and mentor newer volunteers. Daniel, meanwhile, continues to handle live shows and sometimes works in guest services.

One of his favorite things to run, he said, is the gadgets cafe, where guests receive "menus" with science experiments that are "served" at their tables for them to complete.

The best-seller, Daniel said, is the flubber, a gooey slime mixture that guests can make and take. Also among the menu options are seltzer rocket-making and computer disassembly.

"I've gained a much better general knowledge of science," Daniel said. "I've met so many people around Columbus who are as passionate about science as I am."

Outside of COSI, the Tai siblings stay active with several other volunteer and extracurricular projects.

Daniel plays on the Darby tennis team, plays the violin in a local music group and is a member of his school's engineering and math club. He also has volunteered at his church's food pantry.

Elli, too, is active at the family's church, where she volunteers at the food pantry and performs on Sundays with the worship band. As a member of the National Honor Society during high school, she worked often on service projects.

"It's not just living your own life – we're part of this complex network," she said. "It's important that we find ways to give back to it and get involved with it."

elagatta@dispatch.com

@EricLagatta