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The increasing power and smaller size of electronic devices have made it more difficult to remove the heat generated by their processors. Liquid cooling can help manage this heat, but it requires compact pumps that can circulate coolant through narrow cooling channels. In ultra-thin laptops, these pumps may need to be less than 5 mm thick and still provide enough flow and pressure to overcome resistance in the cooling system.
Conventional motor-driven micropumps are usually designed in two stages. Engineers first develop the hydraulic components, including the impeller and flow channels, and then select a motor capable of providing the required speed and torque. This approach becomes less effective as pump dimensions decrease because the hydraulic and electromagnetic components compete for the same limited space. Changes to the impeller geometry affect both the hydraulic load and the space available for the motor, making it difficult to optimize the two systems independently.
In a recent research paper published in Journal of Micromechanics and Microengineering, Dr. Tianfeng Liu, Dr. Song Xue, Dr. Weiwei Liao and Professor Xiaobing Luo from Huazhong University of Science and Technology, together with Dr. Qi Chen from Huake CoolCore (Shanghai) PowerTech Co., Ltd, developed an ultra-thin micropump using a new hydraulic-electromagnetic co-design method. Their approach optimizes the pump and motor together to achieve high hydraulic performance within a very limited space. The prototype measures 34 × 34 × 4.9 mm and delivers approximately 100 mL/min against a pressure difference of 13.05 kPa, consuming less than 1 W of electrical power.
Experiments and Findings
The micropump uses an outer-rotor brushless motor with its rotating magnetic components integrated into the impeller assembly. Instead of transmitting power through a separate motor shaft, the impeller rotates around a fixed central shaft, which reduces the space needed for the driving mechanism. The inlet and outlet are also positioned along the side of the pump housing to minimize its thickness.
The compact design also required a way to support the impeller and control its movement during rotation. The shaft and bearing provide radial support, and the magnetic attraction between the stator and rotor helps keep the impeller in position along its axis. The shaft has a rounded end that reduces contact with the bearing and limits rotational resistance. Ceramic materials were used for the shaft and bearing because of their resistance to wear and corrosion. To establish the hydraulic design, the team first used empirical relationships to estimate suitable impeller dimensions, blade geometry, and flow channel characteristics. The authors used computational fluid dynamics simulations to calculate the flow and pressure generated by the rotating impeller and these calculations provided a starting point for evaluating the motor requirements.
The design process involved matching the hydraulic requirements with the motor’s electromagnetic performance. Both components operate at the same rotational speed, and the motor must provide enough torque to drive the impeller and their dimensions are also closely connected. For example, the team found increasing the blade height reduces the space available for the magnetic rotor and stator, potentially affecting motor efficiency. The researchers used repeated hydraulic and electromagnetic simulations to balance these competing requirements.
The authors performed simulations to identify several geometric factors affecting pump performance and observed blade dimensions and flow channel geometry influenced how effectively the impeller transferred energy to the liquid. Larger clearances between moving and stationary components reduced pressure generation and hydraulic efficiency, so the researchers kept these gaps as small as manufacturing tolerances allowed. They found increasing the number of blades improved pressure generation but also required more torque and made manufacturing more difficult. They selected a total of 41 blades to balance all these factors.
After the researchers finalized optimization, the simulated pump generated a pressure difference of 15.01 kPa, compared with 11.5 kPa for the initial design. Hydraulic efficiency also increased from 3.63% to 5.17%. The optimized impeller produced higher liquid velocities and a faster pressure increase along the flow channel, transferring more energy to the coolant. This additional energy transfer outweighed the associated fluid losses.
The motor was designed to provide sufficient torque at the target speed of 6,000 rpm. The researchers also adjusted the hydraulic and electromagnetic components so that both operated near their highest efficiency at this speed. To test the optimized design, the team fabricated a prototype and evaluated its performance in a closed water circulation loop. The measured pressure was slightly below the simulated value, but the experimental pressure-flow characteristics followed similar trends to the simulations.
Engineering Significance
The new proposed method by Huazhong University of Science and Technology scientists can help engineers develop compact micropumps that balance hydraulic performance, motor efficiency, and size requirements. This is especially useful for ultra-thin cooling systems, where even small changes in component dimensions can affect the performance of the entire pump.
The first of its kind approach also incorporates mechanical clearances, structural requirements, and manufacturing constraints during optimization and instead of searching for an absolute optimum across every possible design combination, it identifies feasible solutions that meet the required hydraulic performance and dimensional specifications. This makes the method useful for developing compact rotary pumps that can be manufactured and assembled.
The vortex pump must be filled with liquid before operation because it cannot prime itself. To prevent air from accumulating in the cooling circuit, the researchers recommend vacuum filling during manufacturing, placing the pump at the lowest point of the circuit, and adding a vent to remove trapped air.
The co-design method may also be applied to pumps with different thickness requirements, including designs approaching 3 mm. At smaller dimensions, manufacturing and assembly precision become increasingly important in determining the achievable performance.
Reference
Liu, Tianfeng & Xue, Song & Liao, Weiwei & Chen, Qi & Luo, Xiaobing. (2026). An ultra-thin plate-level micropump with hydraulic-electromagnetic co-design methodology. Journal of Micromechanics and Microengineering. 36. 10.1088/1361-6439/ae5c13.
