Demonstration of thermal modulation using nanoscale and microscale structures for ultralarge pixel array photothermal transducers

Ultralarge Pixel Array Photothermal Film based on 3D Self-Suspended Microbridge Structure for Infrared Scene Projection

Infrared emitter is highly desirable for applications in infrared imaging and infrared stealth technology. It is also a core device in infrared scene generation. Light-driven photothermal film has attracted considerable interest due to its outstanding photothermal properties and easy fabrication. However, the existing photothermal films suffer from low photothermal conversion efficiency (PCE) as well as small sizes. The improvement of the PCE is usually achieved at the expense of dynamic frame rate. Here, this work designs and fabricates a photothermal film based on 3D self-suspended microbridge structure. Silicon (Si) microbridges are introduced into each microstructure to manipulate the thermal conductivity of the films. By optimizing the parameters of the Si microbridges, the high PCE and fast frame rate are both achieved. Moreover, the 3D structure microbridge film is 4-inch in diameter, forming an ultralarge array with over 2200 × 2200 pixels. Finally, a high PCE infrared scene projector is realized based on this photothermal film. A visible image is projected on the film, the 3D-microstructured photothermal film absorbs the visible light and emits an infrared image same as the visible one with high resolution and fast frame rate due to the excellent photothermal properties.

Linear extrapolation method based on multiple equiproportional models for thermal performance prediction of ultra-large array

Strong demand for developing the photothermal (PT) and electrothermal devices with ultra-large array is increasing. Thermal performance prediction is vital to optimize the key properties of the devices with ultra-large array. Finite element method (FEM) provides a powerful numerical approach for solving complex thermophysics issues. However, for calculating the performance of devices with ultra-large array, it is very memory-consuming and time-consuming to build an equal scale three-dimensional (3D) FEM model. For an ultra-large periodic array irradiated with a local heating source, the use of periodic boundary conditions could lead to considerable errors. To solve this problem, a linear extrapolation method based on multiple equiproportional models (LEM-MEM) is proposed in this paper. The proposed method builds several reduced-size FEM models to carry out simulation and extrapolation, which avoids dealing with the ultra-large arrays directly and greatly reduces the computation consumption. To verify the accuracy of LEM-MEM, a PT transducer with beyond 4000 × 4000 pixels is proposed, fabricated, tested and compared with the prediction results. Four different pixel patterns are designed and fabricated to test their steady thermal properties. The experimental results demonstrate that LEM-MEM has great predictability, and the maximum percentage error of average temperature is within 5.22% in four different pixel patterns. In addition, the measured response time of the proposed PT transducer is within 2 ms. The proposed LEM-MEM not only provides design guidance for optimizing PT transducers, but is also very useful for other thermal engineering problems in ultra-large array that requires facile and efficient prediction strategy.