Magnetically Responsive Multidimensional Thermal Display Using Liquid-metal-based Flexible Thermal Switches

Traditional thermal switches regulate thermal conductivity only in a single global direction, which limits their application in infrared thermal display. This study presents a flexible thermal switch composed of magnetic liquid metal, polydimethylsiloxane (PDMS), graphene films, and polyvinyl chloride (PVC) films. The magnetic field can regulate the distribution of magnetic liquid metal, thereby adjusting thermal conductivity of the flexible thermal switch. The thermal conductivity can be switched between 0.245 and 1.546 W·m-1·K-1, corresponding to a thermal switching ratio of 6.3. The flexible thermal switch can be applied to multidimensional thermal display, which enables independent regional regulation by magnetic field. Regions exposed to a magnetic field exhibit high thermal conductivity, whereas regions without magnetic field maintain low thermal conductivity. Finite element simulation demonstrates that alphabetic thermal patterns from A to Z can be achieved through regional modulation of thermal conductivity. Experimentally, a "THU" thermal pattern is generated by moving a magnetic pen and visualized using infrared thermal imaging. This work overcomes the limitation of conventional thermal switches that permit only global regulation in a single direction, offering new opportunities for smart thermal management, information display, and infrared camouflage.