Source: Budlayan et al., 2025

MANILA - Filipino researchers have developed a low-cost, easy-to-make water-based liquid lens that can be adjusted dynamically, opening up possibilities for its use in classrooms, laboratories, cameras, and wearable technology.

In a study published in the May 2025 issue of the journal Results in Optics, researchers led by Marco Laurence M. Budlayan and Dr. Raphael A. Guerrero showed that it is possible to create tunable liquid lens by simply adjusting the volume of a water droplet.

“Varying the water droplet volume changes the beam width without replacing any optical components,” the researchers wrote in their abstract. 

Source: Budlayan et al., 2025

To achieve this, the scientists coated ordinary glass slides with very fine fibers of polyvinyl chloride (PVC) plastic using a technique called electrospinning. This process made the surface hydrophobic, or water repellent, allowing water droplets to maintain a curved, dome-like shape similar to a lens. 

The study explained that when a laser beam was passed through the droplets, the width of the beam altered depending on the size of the droplet. “Results revealed an increase in the beam size with increasing droplet volume manifesting a defocusing or magnifying effect as the beam passed through the droplets,” they stated.

Essentially, the optical beam maintained its Gaussian profile--which means the beam’s shape and quality stayed consistent even as it was widened or magnified by the droplet. This meant that the technique did not significantly distort the beam. 

By using water droplets with volumes ranging from 5 to 60 microliters (µL), the researchers were able to mimic the action of a convex lens with different focal lengths. “By using droplets with different liquid volumes (5–60 µL), we replicate the action of a convex lens with varying focal length,” the paper noted.

The scientists further demonstrated that larger droplets acted like lenses that pushed the beam, focusing farther away (longer focal length), while smaller droplets produced a tighter focus. They were even able to control the direction the beam dispersed by moving the position of the droplet, offering simple yet effective beam steering capabilities. 

The researchers stressed that the system they developed is inexpensive and accessible. 

Unlike other more complicated and costly tunable lens systems which often require electronics, pressure control, or microfluidics, the new discovery presented only requires simple materials and no external power or moving parts, they said.