On January 3, 2024
Heat Problem in Electronics
Modern electronics suffer from a heat problem, as modern computer chips contain small “hot spots” that have energy densities surpassing that of rocket nozzles and approaching that of the surface of the sun. As a result, more than half of the total electricity consumed in data centers in the United States is used for cooling. Many promising new technologies, such as 3D-stacked circuit chips and renewable energy systems, are hindered by excess heat that reduces device performance, reliability, and lifespan.
Invention of Heat Control Circuits
The solution may have been found by Dr. Yongqi He and his team. According to a report published last November in the journal Science, his team has developed a new type of transistor that can precisely control the flow of heat by exploiting the fundamental chemistry of atomic bonding at the molecular level. These “thermal transistors” are likely to be a key component in future circuits and will work alongside electrical transistors. He states that the new device is already available, scalable, and compatible with current industrial manufacturing practices, and it could soon be integrated into the production of lithium-ion batteries, internal combustion engines, semiconductor systems (such as computer chips), and more.
Precise Heat Control
Electrical transistors were invented in 1947 and changed the world by enabling engineers to precisely control electricity. These devices, which have become a critical part of almost all electronics, act as switches: they consist of two terminals through which electric current flows, along with a third terminal that controls that flow. Today, billions of transistors can be packed onto a single chip, and while these reductions have dramatically increased computing power, they have also made dealing with excess heat more challenging.
With the right technology, wasted heat can be harnessed to prevent chip damage, and it can also be captured and reused. Alex Zettl, an experimental physicist at the University of California, Berkeley, who was not involved in the new study, says, “Currently, most heat in electronic circuits is seen as a nuisance, and one simply tries to direct it away, whereas it really needs to be exploited.” He adds that in the future, it is suspected that electronic and thermal circuits will work together.
Challenges in Designing the Thermal Transistor
Over the past two decades, research teams like He’s have attempted to achieve this future by developing thermal transistors to control heat flow with precision that exceeds electrical transistors’ control of electrical currents. However, they faced several fundamental challenges. For example, previous designs of thermal transistors often relied on inflexible moving parts that slow down processing speed. Structural issues also caused such devices to fail. He states, “There was a lot of interest in this area, but there were no successes.”
New Design for the Thermal Transistor
To overcome these limitations, He and his colleagues spent a decade developing a completely new approach to building the thermal transistor. Their technology utilizes the bonds formed between atoms in a nanometric channel of the new transistor. These bonded atoms are held together by sharing their electrons, and the way these electrons are distributed among them affects the strength of the bonds. This, in turn, affects the amount of heat that can pass through the atoms.
He and his colleagues found that they could manipulate these variables using a nanometric electrode that applies an electric field to precisely control the flow of heat. Similar to the electrical transistor, the new device consists of two terminals through which heat flows and a third terminal that controls this flow, in this case, using the electric field that modifies the interactions between electrons and atoms within the device. This leads to changes in thermal conductivity and allows for precise control of heat flow.
Control
In Heat with Precision
With the invention of the device, he says, we can now “manipulate heat for many applications according to our needs.” This includes preventing the computer from overheating and even reclaiming that wasted energy for reuse.
The new device has achieved a record and performed better than several diseases of recently engineered thermal transistors that do not use bonding at the atomic level. Its “new and elegant” design directs the cooling power to specific areas with “excellent” speed, according to Joseph Hermans, an experimental physicist at Ohio State University, who did not participate in the research. In experiments, the team found that the new device significantly suppressed heat spikes by 1300% and achieved all this control with high reliability.
Jeff Wihemayer, a mechanical engineer at Rice University, who also did not participate in the new study, adds that the new technology for manipulating the bond between atoms using electricity to control heat will stimulate “a lot of future fundamental research.”
Future Challenges and Potential Applications
There is still much work to be done before the new device can “change the world,” according to Zeitl. A critical step is that future research must first create fully integrated thermal electronic circuits, which requires integrating the new heat control circuits with existing electrical circuits. But Zeitl believes that the new device achieves the core goal of “elegantly linking electronics with the flow of thermal energy, which is the ultimate long-term goal.”
He and his colleagues are already conducting experiments on the device’s structure and materials to further improve its performance. They are also exploring ways to integrate it into various systems, including three-dimensional stacked circuit chips. These arrangements address the fundamental gradient challenge by stacking two-dimensional chips, but they present unique challenges in cooling.
The small thermal transistors may also have medical heat control applications. Ho’s team is working with oncologists to investigate whether thermal transistors can enhance a type of cancer treatment called hyperthermia, which uses magnetic particles to deliver lethal levels of heat to malignant cells. Ho says thermal transistors could potentially be integrated into exploration devices or nanoparticles to provide oncologists with precise control over heating, ensuring the destruction of cancer cells while preserving healthy body cells.
Ho predicts that thermal transistors, just like the invention of the electrical transistor, will lead to currently unimaginable surges in the field of innovation. “This invention opens up tremendous opportunities in heat management and processing, as well as new computing models. Thermal transistors are a gateway to the future,” says Ho.
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