Tokyo: To understand the effects of microgravity on crystal growth, a team of Japanese researchers has measured the growth of crystals in a specially-designed chamber on board the International Space Station (ISS).

The researchers monitored the very slow growth and dissolution rate — approximately one centimetre per second of the crystals by a method called laser interferometry.

This was the first time the technique had been used onboard the orbiting international laboratory to measure the growth rate of the crystals at various temperatures.

“We are interested in the growth mechanisms of a space-grown protein crystal — a lysozyme crystal — as a model crystal to understand why space-grown crystals sometimes do show better quality than the Earth-grown crystals,” explained Tomoya Yamazaki, PhD student in Katsuo Tsukamoto’s lab in Tohoku University’s department of earth and planetary science in Sendai, Japan.

To observe this, Yamazaki and his colleagues developed unique growth cells suitable for long-term projects for about six months.

For the researchers studying protein crystal growth, that distance was 250 miles up — the altitude at which the ISS orbits the Earth.

The experimental process, known as NanoStep, was performed in the Japanese Experimental Module (KIBO) of the ISS.

Tsukamoto and his colleagues had previously measured the growth rates of protein crystals under simulated microgravity by using a Russian recoverable satellite and aircraft in parabolic flights.

The researchers took precise measurements of the growth rate of the lysozyme crystals versus their driving force and supersaturation. This also yielded crucial information about the growth mechanism.

Tsukamoto and his colleagues detailed the growth method in the journal Review of Scientific Instruments.

While the researchers expected growth rates of the crystal solution to be slower because of the suppression of solution convection, the results instead showed an increased growth rate.

Extended projects for the researchers using the same apparatus to test the growth of different crystals, such as glucose isomerase crystals, are currently in preparation.