The freeze-ray gun, famously associated with the Batman villain Mr. Freeze, has potentially found its real-life counterpart, thanks to a breakthrough by University of Virginia professor Patrick Hopkins. However, rather than being intended for weaponry, Professor Hopkins' discovery revolves around the utilization of heat-generating plasma to achieve on-demand surface cooling for electronics within spacecraft and high-altitude jets. This cutting-edge innovation seeks to address the critical cooling needs of advanced technology in extreme environments.
According to Professor Hopkins, the lack of efficient cooling methods is currently a significant challenge for electronic systems. Many onboard electronics tend to overheat without proper cooling mechanisms.
The United States Air Force sees great potential in the freeze ray concept, leading them to award Professor Hopkins' ExSiTE Lab (Experiments and Simulations in Thermal Engineering) a substantial $750,000 grant over three years to explore and optimize this innovative technology.
Following the research phase, the lab will collaborate with Hopkins' UVA spinout company, Laser Thermal, to develop a functional prototype of the cooling device. This partnership aims to turn the theoretical concept into a practical and tangible solution for advanced electronic cooling in various applications.
The professor elaborated that electronics on military aircraft and terrestrial vehicles can often rely on natural cooling methods due to their proximity to the Earth's surface. For instance, the Navy employs ocean water as part of its liquid cooling systems, while aircraft components closer to the ground benefit from the denser air to maintain lower temperatures.
However, challenges arise for the Air Force and Space Force, as they operate in space, where a vacuum prevails, or in the upper atmosphere, with very limited cooling air. Consequently, electronic components in these environments continue to heat up without effective cooling mechanisms. Introducing a payload of coolant is impractical since it would add weight and decrease efficiency.
Nonetheless, Professor Hopkins is making progress towards a lightweight solution. His research, in collaboration with others, has led to a review article discussing this technology's potential and other prospects in the journal ACS Nano. This indicates promising strides towards developing a viable cooling solution for electronics in extreme environments.
The Fourth State of Matter
The everyday matter we encounter can be categorized into three states: solid, liquid, and gas. However, there exists a fourth state known as plasma. Though relatively uncommon on Earth, plasma is the most prevalent form of matter in the universe, constituting the building blocks of stars.
Plasma is formed when gas is energized, leading to its distinctive properties, which vary depending on the type of gas and prevailing conditions. Nevertheless, all plasmas share a common feature: an initial chemical reaction that liberates electrons from their nuclear orbits, resulting in the release of a dynamic stream of photons, ions, electrons, and other energetic species. This process sets plasma apart as a distinct and fascinating state of matter with diverse and unique characteristics.
The astounding effects of plasma can be observed in various phenomena, such as the sudden brilliance of a lightning strike or the captivating glow of a neon sign.
Although plasma screen televisions were once popular and later phased out, it would be a mistake to underestimate the growing significance of plasma in technology. Presently, it finds application in the engines of several of the Air Force's high-speed jets. By aiding combustion, plasma enhances both speed and efficiency.
However, Professor Hopkins envisions a broader potential for plasma, not just limited to engine use. He sees it being harnessed for the interior of spacecraft as well, opening up new possibilities for its implementation and benefits in aerospace technology.
Traditionally, air and space electronics have relied on a "cold plate" approach to manage heat. This method involves conducting heat away from the electronic components towards radiators, where it is then released. However, for more sophisticated electronics, this solution may no longer be adequate.
Professor Hopkins proposes a revised setup that could involve a robotic arm equipped to respond to temperature fluctuations. This robotic arm would feature a short, close-up electrode capable of targeting and zapping specific hot spots.
The plasma jet employed in this innovative solution acts akin to a laser beam or lightning bolt, exhibiting remarkable precision and localization. Its ability to target and address heat issues in an extremely focused manner could revolutionize the way advanced electronics are cooled, ensuring optimal performance and reliability in challenging environments.
The Plasma Enigma
Fascinatingly, plasma exhibits an incredible range of temperatures, capable of reaching levels as scorching as the sun's surface. However, it possesses a rather peculiar trait-;one that seemingly challenges the principles of the second law of thermodynamics. When plasma comes into contact with a surface, it undergoes an unusual process where it initially cools before eventually heating up.
This unexpected revelation was made by Professor Hopkins and his collaborator, Scott Walton, from the U.S. Navy Research Laboratory. The discovery occurred several years prior to the onset of the pandemic, adding to our ever-expanding understanding of this enigmatic state of matter.
Plasma is truly captivating, boasting an astonishing temperature range that can rival the scorching heat found on the sun's surface. What sets it apart is a rather curious characteristic-;one that appears to challenge the fundamental principles of the second law of thermodynamics. Upon contact with a surface, plasma undergoes an intriguing process: it cools initially before eventually transitioning into a heating phase.
Professor Hopkins and his collaborator, Scott Walton, from the U.S. Navy Research Laboratory, were the ones who stumbled upon this unexpected revelation. Their groundbreaking discovery took place several years before the pandemic emerged, contributing significantly to our ever-expanding knowledge of this mysterious state of matter.
According to Professor Hopkins, when they activated the plasma, they instantly measured the temperature at the point of impact and observed the surface's immediate response. To their surprise, the surface cooled down initially before gradually heating up.
The team found themselves perplexed by this recurring phenomenon, as there was no existing literature or prior research that could provide insights into such rapid and precise temperature changes. The novelty of their observations made it a unique and puzzling discovery, as no one had previously been able to measure temperature variations with the level of precision they achieved in such a short span of time.
What They Realized
Through collaborative efforts, together with then-UVA doctoral researcher John Tomko and further experimentation at the Navy lab, the team eventually unraveled the underlying mechanism behind the surface cooling phenomenon. They concluded that the cooling effect was attributed to the plasma's ability to blast an ultrathin surface layer, barely visible, composed of carbon and water molecules.
This process is reminiscent of what occurs when cool water evaporates from our skin after a refreshing swim, causing a cooling sensation. The understanding of this unique interaction sheds new light on the intriguing behavior of plasma and provides valuable insights for potential applications in various fields.
According to the professor's explanation, the evaporation of water molecules from the body necessitates energy, drawing heat from the body and resulting in a sensation of coldness. In the case of plasma interacting with the surface, it removes the absorbed species, liberating energy in the process, which leads to cooling.
Professor Hopkins employs a technique known as "time-resolved optical thermometry" in his microscopes. These instruments measure a property called "thermoreflectance" to study and analyze the temperature changes and thermal behavior during plasma interactions. This advanced method allows for precise and detailed observations, enabling a deeper understanding of the intriguing surface cooling phenomenon.
Essentially, the way the surface material reflects light varies based on its temperature: hotter surfaces exhibit different light reflections than colder ones. To study this phenomenon, a specialized scope is necessary, as the intense plasma would otherwise destroy any conventional temperature gauges that come into direct contact with it.
The team managed to achieve a temperature reduction of several degrees for a brief duration of a few microseconds. Although it may not appear dramatic, this cooling effect holds significance for certain electronic devices. Even a small decrease in temperature, albeit for a short time, can make a noticeable difference in improving the performance and longevity of such electronic components.
Following the pandemic-related delay, Professor Hopkins and his collaborators published their preliminary findings in Nature Communications the previous year.
Subsequently, they faced a new challenge: Can they extend the duration of the reaction and achieve even lower temperatures?
Refining the Freeze Ray
Having previously utilized borrowed equipment from the Navy, which was lightweight and safe enough for school demonstrations, the UVA lab has now acquired its dedicated setup, courtesy of the Air Force grant.
With their new resources, the team is focused on enhancing the apparatus by exploring various modifications to their original design. Doctoral candidates Sara Makarem Hoseini and Daniel Hirt are actively investigating different gases, metals, and surface coatings that can be targeted by the plasma, aiming to optimize and expand the capabilities of the Freeze Ray technology.
Hirt shared an update on the lab's progress.
"We're currently focused on helium and haven't delved into exploring other gases just yet," he explained. "Our experiments have involved various metals like gold and copper, as well as semiconductors. Each material presents a unique opportunity to study how plasma interacts with its distinct properties, creating a fascinating playground for our research."
"By varying the gas used in the plasma, we can observe the specific influence of each particle on material properties," Hirt explained.
Working alongside Professor Hopkins on a project with immense implications has revitalized his passion for research. Much of this newfound enthusiasm can be attributed to the supportive and encouraging lab environment fostered by the professor.
Hirt expressed, "It feels like a complete transformation, not only in my development as a scientist but also in my enjoyment of science. The contrast between where I was before and where I am now is like night and day."
Source: https://www.virginia.edu/