Researchers have developed a miniature boat with three acoustic cavities tuned to different audio frequencies. By adjusting the frequency of sound waves produced by external speakers, they can steer the boat in a specific direction. The team also created a 3D-printed microflyer with three integrated cavities tuned to ultrasonic frequencies. These cavities generate upward thrust and aerodynamic lift, allowing the device to move much like a miniature helicopter.
Science Advances, 2026. DOI: 10.1126/sciadv.aef5620.
Cooling without electricity
Credit: Yi-Ting Hsiau and Jingyuan Xu, KIT/Ella MAR Studio
Conventional refrigerators and air-conditioning systems use the Carnot cycle. An electrically powered compressor moves heat from a high-pressure chamber to a low-pressure chamber through a refrigerant gas. Although effective, this approach is not perfectly efficient. Inventors including Albert Einstein and Leo Szilard have explored alternatives, including the patented Einstein-Szilard refrigerator, an energy-efficient absorption system with no moving parts.
The latest development is a thermally driven elastocaloric cooling system that can use waste heat or solar energy instead of electricity. The breakthrough technology is described in a paper published in Nature Energy.
Elastocaloric cooling systems rely on shape-memory alloys that heat up when mechanical stress is applied and cool down when the stress is released. Existing systems typically use electrically powered actuators to apply that force. The authors of the Nature Energy study found a potential solution by bonding two ultrathin nickel-titanium films together.
The first film is engineered to contract when heated, converting thermal energy into mechanical work without an electric motor. Its movement is transferred to the second film, triggering a reversible change in the material’s crystal structure and producing a cooling effect.
This design could enable solid-state cooling powered by waste heat or sunlight. The current prototype demonstrates the feasibility of the technology, but additional research is needed to increase its cooling capacity by connecting multiple films. If the system can be scaled effectively, it could use waste heat to cool computer processors or capture heat from vehicle drivetrains to protect sensitive automotive electronics.
Nature Energy, 2026. DOI: 10.1038/s41560-026-02122-6.
Source: arstechnica.com