outh China Morning Post recently published an interview with Jiao Niandong, a professor at the State Key Laboratory of Robotics, Shenyang Institute of Automation, at the Chinese Academy of Sciences, in Shenyang.
Dr. Niandong develops microrobots, using green algae as his building blocks. His research paper was recently the cover article in the scientific journal Lab on a Chip published by Britain’s Royal Society of Chemistry, and is drawing attention.
His research team found a way to control algae’s movement in water. They built a device to demonstrate its feasibility. The device has a sandwich structure, with the top and bottom layers being glasses coated by light-sensitive films, and the middle a cell platform containing living colonies of algae in fluid.
They directed light beams on the films. The films converted the energy of photons (particles of light) to electricity, and the electric fields generated a hydraulic force in the water of the cell platform. They used the hydraulic force to confine, direct and manipulate movement of algae cells — that took orders from humans and behaved well as microrobots.
This is the first time that live algae cells have been trapped and formed into a micrometer-sized motor array. Why algae?
From an engineer’s point of view, each alga is a microrobot. It can feel the environment and move around. It absorbs energy from the surroundings and converts chemical power to mechanical drive.
Algae are also fast swimmers. In the experiment, we used a common species called Chlamydomonas reinhardtii, which was about 10 micrometres in size but could swim a distance more than 10 times its body length in a second. In our bigger world, that speed was equivalent to a car running at 180 kilometers per hour.
How does the alga swim?
An alga has a pair of lash-like antennas known as flagella. It moves constantly by paddling the flagella in water like a swimmer swinging a pair of very long arms. But the movement is spontaneous, the direction aimless. How to confine and control algae’s movement has challenged researchers for many years.
Conventional techniques such as trapping with mechanical, acoustic, electrostatic and magnetic forces were only used to capture lifeless particles and non-swimming cells. Some researchers proposed [using] laser, but the high energy of a laser beam could injure or kill the algae. Our method did not require a direct physical contact to the algae, and the light we used is gentle, harmless.
How did the algae respond to your command?
We made them stay within a circular fence of light, like keeping cattle in a range. We moved them from one place to another by moving a light beam. When the beam stops, they swim around the light dot. The speed of the rotation changed as we changed the intensity of light.
What’s the use of turning algae into microrobots?
Microrobots can move and carry cargo at the micro scale. If a microorganism can travel in a straight line, or any course designated, it can become an efficient transporter for various purposes, such as drug delivery. [Microrobots] can also work as construction workers to build complex structures such as bioactuator and biological chips.
When an alga rotates, as we demonstrated in the experiment, it becomes a motor. When many colonies of algae rotate together, they make a powerful array of motors. The rotation, if coordinated and laid out well, would be able to stimulate fluid flow and generate power for other mechanical devices.