Ultra-thin cooling solution for mobile devices

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

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

A loop heat pipe (LHP) is an 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, including a “reservoir” that 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, enabling liquid to continuously move through the system in a loop. This allows it to transfer heat over longer distances and handle higher heat loads, making it suitable for advanced electronics. The system transports heat without the use of electricity by utilising 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 mobile devices are held. 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 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. This indicates that the new device has high cooling power despite its thinness. In addition, because it adheres to the international standard size for smart (contactless) cards, the UTLHP can be used for smart cards in the future.

With a thickness of 0.3 mm, the UTLPH fits within slim modern phones without making them heavier, works effectively regardless of how the phone is held and can also 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. 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,” said Professor Hosei Nagano.

Image credit: iStock.com/Biserka Stojanovic