CASPER scientists unlock the mysteries of smart fluids

June 25, 2020
Our Research - PK4

A team of researchers led by CASPER director Dr. Truell Hyde and CASPER Associate Director Dr. Lorin Matthews recently conducted their first fundamental complex plasma physics experiments employing the Plasma Kristall-4 (PK-4) experiment on board the International Space Station. Campaign #7 (in PK-4 ISS parlance) explores the fundamental origins of order and chaos in a complex plasma (where in this case, the complex plasma is operating as a smart fluid) under microgravity conditions. One additional experiment on board the ISS is scheduled as part of a research project funded by the NSF and NASA.

From advanced shock absorbers in automobiles to soft robotic components and artificial heart valves, smart fluids are revolutionizing many aspects of modern-day life. The primary reason for this is the fact that smart fluids have the unique ability to change their mechanical properties when acted upon by electric or magnetic fields. However, the exact mechanisms allowing the atoms and molecules in these fluids to ‘react’ to such small changes in the surrounding environment is still not well understood.

To tackle these questions, scientists from CASPER designed a series of experiments where small spherical particles, just three micrometers in diameter, were inserted into a plasma environment. The spheres (or dust grains) serve as proxy atoms to allow examination of self-organizing systems in complex fluids. The CASPER team is studying the fundamental principles of order and stability in the resulting dust-plasma structures using video data collected by high-speed cameras to examine how the charged spheres respond to changes in their environment. Performing the experiments on board the International Space Station (ISS) negates the effect of gravity, which normally prevents levitation of the spheres in the central bulk of the plasma. The data received from PK-4 ISS Campaign 7 will allow investigation of how complex plasma fluids change their structure from homogeneous (or smooth) to filamentary (string-like) when acted upon by electric fields. Analysis of the data from these experiments may also unlock new applications for devices using electrorheological fluids on Earth, which also undergo similar homogeneous-to-string transitions.

About the PK-4: Plasma Kristall 4 is the first natural science experiment performed on the ISS and the longest-running series of experiments in the history of human spaceflight. PK-4 (the fourth generation of Plasma Kristall devices) is the first experiment of this series with direct involvement of US research teams, including the CASPER group. The experiment described was funded by a NSF/NASA collaboration through grants NSF PHY 1740203 and NASA 1571701.

About CASPER: CASPER consists of six independent research groups that conduct theoretical, numerical, and experimental research across various fields, ranging from complex plasma physics, space physics and engineering, cosmology, early universe physics and educational research and outreach.

About the ISS: The ISS is the largest human-made object in low orbit around the Earth. It has been continuously inhabited by humans for the past 22 years and is paving the way for establishing a permanent human presence on the surface of the Moon and Mars.

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