Third-year Frankie Fun and 4th-year Mykhaylo Usatyuk head a team of UChicago scientists who illustrated how to evaluate a range of objects – polyethylene and ceramic spheres, glass bubbles, lint strands, glass bubbles, thistle seed, between a warm plate and a cold plate in a vacuum chamber.
“They prepared lots of intriguing observations that blew my mind,” says Cheng Chin, a lecturer of physics, whose ultra-cold lab in the Gordon Centre for Integrative Science was house to the studies. In their study, scientists accomplished a number of levitation breakthroughs, in terms of orientation, duration and method. The levitation lasted for more than an hour, as opposed to a few minutes, stability was accomplished vertically and radially, as opposed to just vertically, and it employed a temperature gradient rather than magnetic or light field.
“Magnetic levitation just works on magnetic particles, and optical levitation only works on objects that can be polarized by light, but with our first-of-its-type method, we illustrate a method to levitate generic objects,” says Chin.
In the study, the bottom copper plates was kept at room temperature while a stainless steel cylinder filled with liquid nitrogen served as the top plate. The upward flow of heat from the warm to the cold plate kept the particles suspended indefinitely.
“The big temperature gradient results in a force that balances gravity and lead to stable levitation,” says Fung, the head author of the study. “We managed to quantify the thermophoretic force and found reasonable agreement with what is expected by the theory. This will enable us to enhance the possibilities of levitating distinct sorts of particles by means of a temperature gradient.”
“Our enhanced comprehension of the thermophoretic force will help us to identify the interactions and binding affinities between the particles we observed,” says Usatyuk, a study co-author. “We are excited about the future study directions we can follow with our system.”
The key to avail high levitation stability is the geometrical design of two plates. A proper ratio of their sizes and vertical spacing enables the warm air to move around and effectively capture the levitated objects when they shift away from the centre. Another sensitivity factor is that the thermal gradient requires to be pointing upward, even a misalignment of one degree will greatly diminish the levitation stability.
“Only within a specific range of temperature, pressure gradient and plate geometric factors can we reach stable and long levitation,” says Chin. “Distinct particles also need fine adjustment of the parameters.”
The apparatus delivers a novel ground-based platform to identify the dynamics of astrophysical, biological and chemical systems in a microgravity environment, according to the scientists. Levitation of macroscopic particles in vacuum is of specific interest due to its extensive applications in space, astro-chemical and atmospheric research. “There are ample research opportunities to which our talented undergraduate students can contribute,” says Chin
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