Micro-optical systems inspired by biology
“Our goal is to combine nature’s cool concepts with state-of-the-art science and engineering capabilities to create solutions that are even superior to nature and, of course, better than what is currently available.”
Hongrui Jiang
Professor of Electrical and Computer Engineering
Many of us peer through lenses every day, but the microscopic lenses devised by engineering professors Hongrui Jiang and Dave Beebe aren’t nearly so ordinary. Made of liquid and designed to be self-adjusting, the pair’s “microlenses” are a breed apart from those in eyeglasses and cameras.
Now, the wildly novel lenses could find use in some of today’s familiar techniques and tools, including surgical instruments, microscopes and even, possibly, eye surgeries – thanks to funding from the Discovery Seed Grant Program.
“This whole process creates great opportunities for researchers from different fields of expertise to work together and come up with something very different from the traditional standard,” says project leader Jiang, an electrical and computer engineering professor. “I think it’s very beneficial.”
How microlenses take shape
In its simplest form, a microlens is created from an oil-water interface situated at a circular hole within a ring of polymer material. Below the hole is a water-filled tube, itself ringed by “hydrogel,” a jelly-like polymer that expands and contracts in response to changes in local environmental conditions.
When the hydrogel ring swells, it squeezes the tube of water, causing its surface to bulge upward into the oil and forming a concave lens spanning just millimeters in diameter. When the hydrogel contracts, the water bows downward as a convex lens.
The surface of the water curves in this way, rather than simply spilling over the top, because it is “pinned” between water-attracting and water-repelling regions in the structure, says Jiang.
The Team
Principal Investigator
- Hongrui Jiang, Electrical and Computer Engineering
Investigators
- David Beebe, Biomedical Engineering
- Herbert Chen, Surgery
- Kevin Eliceiri, Molecular Biology
- Jon Gould, Surgery
- Charles Heise, Surgery
- John Vukich, Ophthalmology
- John White, Biomedical Engineering
Hydrogels can respond to a wide range of stimuli, including temperature, pH, light and even proteins, allowing researchers to tune the microlenses’ shapes, and, thus, their focal lengths, without electronics and bulky external controls. Jiang's team will now build upon this basic feature to develop advanced micro-optical systems for industrial, medical and sensing applications.
Applications in surgery
One of their first goals is to develop microlenses for use in surgical tools such as endoscopes. In endoscopy, fiber optic light is directed along a flexible cable, which doctors insert through a cut in the abdomen to view internal organs and tissues. The lenses in today’s endoscopes aren’t adjustable, however, requiring doctors to reposition the cable to zoom in and out.
By using light-sensitive hydrogels, Jiang’s team hopes to produce lenses that doctors could focus simply by tuning the instrument’s light source. This capability would especially benefit laparoscopic surgery, says Jiang.
“If we can offer a tunable lens right at the tip of the cable, surgeons can concentrate on the surgery, instead of having to stop and move the camera,” he says.
The inspiration for the microlenses ultimately comes from natural eyes; still, Jiang is not content simply to copy biology.
“Our goal is to combine nature’s cool concepts with state-of-the-art science and engineering capabilities to create solutions that are even superior to nature and, of course, better than what is currently available,” he says.
The other team members are biomedical engineering professors John White and Dave Beebe; surgery professors Herbert Chen, Jon Gould and Charles Heise; clinical ophthalmology professor John Vukich, and Kevin Eliceiri, leader of the UW-Madison Laboratory of Optical and Computational Instrumentation.