What’s the best way to become a successful materials scientist? Jiaxing Huang says the key is simply to pay attention to the world around you.
Some of Huang’s best research draws inspiration from the materials in his everyday life. Wadded papers in his office trash can sparked the idea of crumpling graphene sheets. Crumpled graphene balls have the same electrical properties as flat graphene sheets but are much easier to disperse and handle and have greater surface area.
For the crumpling process, Huang, materials science and engineering, looked to yet another household item: the humidifier. He and his team created microscopic water droplets dispersed with graphene-based sheets and then blew them through a furnace. As the water quickly evaporated, the thin sheets were compressed by capillary force into near-spherical, paper ball-like particles. “Everyone uses a humidifier in winter,” Huang says. “So this was a Chicago winter weather-inspired idea.”
Huang applies the same “everyday materials” approach to inspire students in his classroom. During a session in his “Introduction to Conducting Polymers” course, Huang asked his students to use their pencils to draw lines on paper. “By using a pencil to draw a line,” he says, “you may have created many graphene-like particles.”
After class a student approached Huang, asking if the pencil-drawn “graphene” could be used as an electronic material. Huang was intrigued. With his teaching assistant and a pair of students in his class, Huang found that the current passing through the line was very sensitive to the bend of the paper. When the paper was bent downwards, the current decreased; bending the paper upwards caused the current to increase.
Fascinated by this finding, the team decided to test the traces drawn with a flexible toy pencil—one that can bend and twist because its graphite is embedded in plastic.
“If there are toxic vapors nearby, the plastic will absorb that and expand,” Huang explains. “When it expands, it will push the graphite particles apart and decrease the electric current. In order to conduct current, the graphite particles have to touch each other.”
By drawing with the flexible pencil, Huang’s team created a type of chemical vapor sensor called a “chemiresistor.” The resistance of their device will change in response to toxic chemical vapors in the vicinity.
Huang was thrilled to see materials innovations from class projects. “These experiments show our students that you can do creative research at a very early stage,” he says. “You can do innovative work before you get a PhD. Just pay attention and keep a curious mind.”
The team’s research was published in Scientific Reports in January. The paper is titled “Pencil Drawn Strain Gauges and Chemiresistors on Paper.”
By Amanda Morris