You might not be familiar with the term “colloids,” but you likely interact with some throughout your daily routines. What are they? Colloids are not pure liquids or pure solids, but rather liquids that have solid particles suspended in them, such as paint, milk and even blood.
On Earth, solid particles could clump together, causing spoilage in the example of food. They could also settle to the bottom of the solution through sedimentation. Removing gravity from the equation, though, makes the environment aboard the International Space Station a perfect place for researchers to study the self-assembly of these particles.
In the Advanced Colloidal Experiment- Heated-2 (ACE-H-2) investigation, researchers are studying a type of colloid that has different sizes of particles suspended within a fluid medium. There are small nanoparticles that are highly charged and large particles that are non-charged. When the suspensions were allowed to settle under gravity, the particles that were stabilized (while in suspension) formed highly ordered, three-dimensional colloidal crystal structures that were composed entirely of the larger, non-charged particles. The nanoparticles remained in suspension but was found to create a charge layer by forming cage or halo around the larger particles. This is a newly discovered process of colloidal stabilization called Nanoparticle Haloing (NPH).
As a result, the ACE-H-2 investigates the nature of the three-dimensional colloidal structures formed by NPH under microgravity conditions, and also assesses the structures when they are heated.
These “self-assembled colloidal structures” are vital to the design of advanced materials, for biomedical applications as an example.
Things have been heating up in the Microgravity Sciences Glovebox (MSG) in the Destiny Lab aboard the International Space Station as NASA astronaut, Tim Kopra performs operations for the BASS-M, a National Lab investigation which came about as a result of a partnership between CASIS and Milliken. Milliken is a commercial company who, among other things, produces custom engineering textiles, including flame-retardant ones used by a variety of industrial markets, such as the military and fire fighters.
Milliken is interested in seeing how the absence of gravity affects the burning of the textiles and materials. They are testing the hypothesis that materials in microgravity, with adequate ventilation, burn as well, if not better than, the same material being burned here on Earth under the same conditions.
The investigation tests 10 different treated flame-retardant cotton fabrics at varying air flow rates, and studies their flammability and their ability to self-extinguish.
Ultimately, Milliken is using innovation in trying to design and engineer the right chemicals so that the textiles don’t burn. This applies specifically to the military and fire-fighters, for whom – if these textiles are designed correctly – could be protected from getting 2nd and 3rd degree burns.