A recent scientific study conducted by a collaborative team of researchers from Nagoya City University (NCU), Japan Space Forum (JSF), Advance Engineering Services (AES), Japan Aerospace Exploration Agency (JAXA), and ANSTO has made a significant discovery related to charged particles in the unique microgravity environment of the International Space Station (ISS). The findings of this study, which was published in the journal npj Microgravity, have important implications for the development of photonic materials, improved drugs, and other innovative materials that rely on the interaction of charged particles.
The researchers aimed to investigate how sub-micron sized charged colloidal particles interact with each other in the presence and absence of Earth’s gravity. They recognized the crucial role played by particle interactions, particularly among charged particles, in various chemical and physical phenomena. For example, the formation of tetrahedral clusters known as diamond lattices, which are essential for producing photonic materials, heavily relies on the self-assembly of colloidal particles. By understanding and controlling this self-assembly process, it becomes possible to create novel materials for applications in photonics, optoelectronics, sensing, and clinical diagnostics.
On Earth, even the slightest gravitational sedimentation and convection can influence particle interactions and their arrangement in a colloid, thereby hindering a comprehensive understanding of the impact of charge. Hence, conducting this study in the microgravity environment of the ISS provided an invaluable opportunity to explore particle interactions in a near-weightless setting.
The knowledge gained from this research has broad implications. It can contribute to the design of more advanced drug formulations with improved stability and efficacy. Additionally, understanding how charged particles interact in microgravity can facilitate the development of new materials with unique properties and functionalities.
During the study, the researchers selected positively and negatively charged lighter particles, as well as heavy particles. Polystyrene particles were chosen as they have a similar weight to the aqueous medium surrounding them, while titania particles were approximately three times heavier than the medium. The samples were immobilized in a gel after their interaction, allowing them to be safely returned to Earth for further analysis and experimentation.
The groundbreaking research has unveiled a surprising discovery regarding the formation of clusters by lighter particles in the microgravity environment of space. It was found that these clusters are 50% larger compared to those formed on Earth, a phenomenon that defied initial expectations.
Moreover, the study confirmed that heavy particles like titania, which are unable to undergo electrostatic interaction and cluster formation on Earth, were indeed capable of doing so in space. This unexpected behavior adds another layer of intrigue to the research findings.
The experimental setup developed for this study was an engineering marvel. Working closely with multiple organizations, the team successfully designed a custom-built apparatus capable of mixing samples in space and subsequently immobilizing them using LED-UV light. The meticulous planning and execution of this setup allowed for the controlled creation and preservation of clusters in a gel-like medium.
To conduct the experiment, two sets of samples were prepared in Japan. One set was sent to the International Space Station (ISS) using a Falcon rocket (Space-X) and the Dragon SpX-19 transporter, while the other set was used for a ground-based experiment. Following the prescribed procedure, the ISS crew mixed the samples and cured them using LED-UV light. After spending over a year in space, the samples were safely returned to Earth and distributed to various institutes for analysis.
ANSTO, renowned for its state-of-the-art reactor-based instruments, Quokka (Small Angle Neutron Scattering – SANS) and Kookaburra (Ultra Small Angle Neutron Scattering – USANS), received a set of these samples. Dr. Mata, involved in the study, praised the uniqueness of these instruments, which provided unparalleled insights into the structural aspects of clusters that are challenging to investigate using other techniques. Leveraging the contrast variation capabilities of SANS and USANS, the researchers gained valuable information about the individual components involved in the clustering process.
The combined data from Quokka and Kookaburra played a vital role in elucidating the structural morphology and charge-charge interaction of colloidal particles across a size range spanning from approximately 1 nanometer to 10 micrometers. Importantly, this analysis was performed without compromising the crystal environment of the samples. The study also employed mathematical modeling and simulations, along with other techniques, to enhance the overall understanding of the observed phenomena.