Wiggly Gels Promise Bright Future

By: Liz Daubenmire

UC Undergraduate’s research on swimming gels is published in a prestigious journal today - Friday, May 30 2014.

Next time you spot an earthworm sliding through fresh dirt, take a closer look. What you’re seeing is an organic movement called peristaltic locomotion that has been meticulously refined by nature.

Jarod Gregory, an undergraduate student in UC’s College of Engineering and Applied Science, used a worm’s contracting and expanding motion to provide a way for gels to swim in water. This is a product of work by the interdisciplinary team consisting of Jarod Gregory, a chemical engineer, and his two advisers, Professor Lilit Yeghiazarian, PhD (environmental engineer) and Professor Vasile Nistor, PhD (biomedical engineer).

Phase one of his research titled, “Remote-Controlled Peristaltic Locomotion in Free-Floating PNIPAM Hydrogels” is published in the Journal of Applied Polymer Science.

In order to use a laser to induce shrinking of the hydrogel, the hydrogel must first adsorb a laser dye that will absorb irradiation from a specific laser. For this system, Jarod coupled the laser dye IR-820 and a 823 nm laser. The fluorescent image above (cross-section of a 5 mm diameter hydrogel) shows that the hydrogel adsorbs IR-820 primarily along its surface.

In order to use a laser to induce shrinking of the hydrogel, the hydrogel must first adsorb a laser dye that will absorb irradiation from a specific laser. For this system, Jarod coupled the laser dye IR-820 and a 823 nm laser. The fluorescent image above (cross-section of a 5 mm diameter hydrogel) shows that the hydrogel adsorbs IR-820 primarily along its surface.

Published research is always an accomplishment within the world of academia, but it is especially significant when the primary author was an undergraduate student at the time of his research. Jarod is an ACCEND (ACCelerated ENgineering Degree) student who has just transitioned directly into the Ph.D. program in environmental engineering last month after earning a Bachelor of Science in chemical engineering. This not-so-common achievement as an undergrad points to the significance of Gregory’s research, also recognized by this year’s Goldwater Award.

When earthworms use peristaltic locomotion they engage with a surface, propel forward, and detach. Jarod explains that peristaltic motion has previously been used by the team as a mechanism for movement for gels in frictional environments such as on solid ground or inside a tube. With Jarod’s research, soft materials now have the ability to move freely without requiring outside friction, by using shrinking and swelling to move the center of gravity of an object in water -- vastly expanding potential applications of soft materials and soon, soft robots.

Jarod explains, “Using a hand-held laser, we were able to selectively and quickly shrink the hydrogel (a hydrophilic polymer gel comprised mostly of water) in desired areas. By inducing a shrinking/swelling cycle down the length of a hydrogel, we were able to successfully mimic peristaltic, or earthworm-inspired, locomotion in water.”

This set of images shows a free-floating hydrogel (2.6 cm in length) moving through water as it shrinks and swells. The light green areas on images b and c are the places in which shrinking is taking place. The red markers on all four images are references to see the overall displacement of the hydrogel.

This set of images shows a free-floating hydrogel (2.6 cm in length) moving through water as it shrinks and swells. The light green areas on images b and c are the places in which shrinking is taking place. The red markers on all four images are references to see the overall displacement of the hydrogel.

According to Gregory, “Studies have shown that
 hydrogels can be equipped to detect bacteria, carry cargo and deliver medicine. This new method of mobility expands the hydrogel’s use as an environmental and biotechnological tool by allowing them to explore new areas such as surface waters to combat toxic elements, or cavities inside the human body.”

This research project started by Jarod Gregory with Professor Lilit Yeghiazarian, PhD, and Professor Vasile Nistor, PhD of the Biomedical, Chemical, and Environmental Engineering Department in January of 2013 is a National Science Foundation - supported project. It was also a part of the NSF Research Experience for Undergraduates program at the University of Cincinnati for the 2013-14 academic year.

As Jarod Gregory continues into the next phase of his research, the world of soft materials is sure to reap the benefits.

For more information about ongoing research at UC CEAS, please visit: http://ceas.uc.edu/research/research_overviewbydept.html