Ultra-thin cooling solution for mobile devices unlocks slimmer, high-performance technology

Scientists from Nagoya University in Japan have developed an innovative cooling device—an ultra-thin loop heat pipe—that significantly improves heat control for electronic components in smartphones and tablets. This breakthrough successfully manages heat levels generated during intensive smartphone usage, potentially enabling the development of even thinner mobile devices capable of running demanding applications without overheating or impeding performance.

The research, published in the journal Applied Thermal Engineering, addresses one of the most critical challenges in mobile device engineering: effectively cooling increasingly powerful components within the confined space of slim mobile devices. The team's solution provides more efficient heat management without increasing device thickness, which could allow manufacturers to push performance boundaries while maintaining or even reducing size. This may lead to next-generation smartphones and tablets that deliver sustained high performance without compromising on design or user experience.

Breaking size barriers

A loop heat pipe (LHP) is a highly efficient passive heat transfer device that can move heat from one location to another without requiring external power. It works like a normal heat pipe but has a more complex structure that provides several advantages. For example, a LHP has a “reservoir” which acts like a storage area for liquid, helping to keep the system stable and ensuring smooth circulation.

Normal heat pipes move liquid in a straight path, but a LHP has a closed-loop design—liquid continuously moves through the system in a loop. This allows it to transfer heat over longer distances and handle higher heat loads, making it ideal for advanced electronics. The system transports heat without the use of electricity by utilizing the capillary action generated by a porous material (sponge structure) called a “wick” to drive a pump.

The ultra-thin loop heat pipe (UTLHP) was made by creating a flow path in thin sheets of copper, including a wick made of sintered copper powder (copper powder compacted into a solid, porous structure using heat or pressure), and laser welding them to form a solid, precise unit. The system uses water as a cooling agent inside thin copper channels. The water absorbs heat, evaporates, moves to a cooler area, condenses back to liquid, and the cycle is repeated.

The UTLHP was tested with different amounts of water in multiple positions to simulate the different orientations in which we hold our mobile devices. The device can stably transport 10 W of heat in vertical and horizontal directions. The size of the condenser in previous UTLHPs was large, making it difficult to mount in mobile devices. In this study, the compactness was optimized based on numerical models from the design stage, achieving three key features: thinness, high performance, and ease of insertion.

When converted into thermal conductivity, the heat transport capacity of the device was approximately 45 times higher than that of copper, and about 10 times higher than graphite sheets. Both copper and graphite are renowned for their excellent thermal conductivity. This indicates that the new device has extremely high cooling power despite its ultra-thinness. In addition, because it adheres to the international standard size for smart (contactless) cards, the UTLHP can be used for increasingly sophisticated smart cards in the future.

Breakthrough from academia-industry partnership

With a thickness of just 0.3 mm, the new UTLHP fits within slim modern phones without making them heavier, works effectively regardless of how you hold your phone, and can handle heat levels for energy-intensive tasks like gaming and video processing.

“The device can potentially extend battery life by keeping components at optimal temperatures and support even thinner designs without compromising performance,” Prof. Hosei Nagano, a researcher at Nagoya University’s Graduate School of Engineering and senior author highlighted. “This achievement could dramatically improve the performance of next generation mobile devices and was done in collaboration with researchers from Porite Corporation, a global powder metallurgy manufacturer in Japan.”

Jun Sasaki, a master’s student at the Graduate School of Engineering and first author, explained the need for advanced thermal management technologies that efficiently dissipate the heat generated in mobile devices. “The development of effective cooling technology is an urgent issue, as heat buildup can lead to reduced device performance, shortened lifetime, and even safety issues,” he said.