CU Boulder's liquid scanning technology can better observe brain activity

CU Boulder published a study in Optical Letters demonstrating a new high-speed laser guidance method for imaging applications, using a fluid scanner built around an electrowetting prism to replace traditional mechanical components.

"Most laser scanners today use mechanical mirrors to steer beams of light," said Darwin Quiroz from CU Boulder.

"Our approach replaces that with a transmissive, non-mechanical device that’s smaller, lower-power and potentially easier to scale down into miniature imaging systems."

Smaller and non-mechanical ways to scan lasers should help meet the demands of modern rapid imaging and fluorescence microscopy systems, where choices are often limited by weight, size and power requirements, noted the team.

These demands are further magnified with the growing interest in miniature microscopy for in vivo imaging of neuronal activity and stimulation.

Darwin Quiroz: new ways to understand the brain

Electrowetting optics could be an answer, using an electric field to change the curvature of a conductive liquid and so control the behavior of a laser beam at the liquid surface. This principle has been put to use in applications such as lidar, but previous work with electrowetting prisms was limited to slow scanning speeds or one-dimensional beam steering.

Transform the study of PTSD or Alzheimer's disease

The project built on previous CU Boulder studies into using such one-dimensional electrowetting scanners in a microscope, and also how to employ the same principle in an OCT platform to improve examination of the eye or the heart.

The new device involves a cylindrical glass tube 5 millimeters tall filled with two immiscible liquids, deionized water and a cyclohexane. Four individually accessible electrodes around the outside of the cylinder control the tilt of the interface between the liquids, so a laser passing through the cylinder from one fluid to the other can be deflected by different amounts when it crosses the slanted interface.

In trials, the device demonstrated two-dimensional scanning at speeds from 25 to 75 Hz when built into a two-photon laser scanning microscope. Successful imaging of 5-micron targets is a milestone toward making the devices practical for real-world imaging, noted the project.

"A big challenge was learning how to drive the device in a way that produces linear, predictable scanning without distortion," commented Quiroz. "We discovered that the prism has resonant modes like standing waves that we could actually leverage for scanning at higher speeds."

Since electrowetting prisms are compact and energy efficient, they could be integrated into miniature microscopes small enough to sit on top of a live animal's head, helping the study of brain function in living subjects.

"Imagine being able to watch brain activity in real-time while an animal runs through a maze," said Quiroz. "That’s the kind of in vivo imaging this technology could enable. It could transform how we study neurological conditions like PTSD or Alzheimer’s disease."

Source: optics.org