Design of a Multifunctional Resin-Based Outdoor Spherical Robot Shell for Ultrahigh Visible to Near-Infrared Transmittance and Mid-Infrared Radiative Cooling.

As robots undertake increasingly complex tasks, such as real-time visible image sensing, environmental analysis, and weather monitoring under harsh conditions, design of an appropriate robot shell has become crucial to ensure the reliability of internal electronic components. Several key factors, such as the cooling efficiency, visible transparency, mechanical performance, and weathering resistance of the shell material, are proposed in this research to ensure future robot functionality. In this study, a polymeric double-layered shell for fabrication by stereolithography 3D printing was designed, featuring a porous outer layer and a spherical inner shell. The inner spherical shell provides approximately 90% transmission in the visible to near-infrared wavelength range (450-1050 nm) and ensures the proper functioning of the optical devices, such as cameras, lidar, and solar cells, inside the robot. In addition, the inner shell material displays high emittance in the mid-infrared range (5-20 μm) to facilitate effective radiative cooling and protect the robot control system from thermal damage. The 3D-printed inner shell is exposed to a real environment for three months, and its stable optical and mechanical performance confirms its weather resistance ability. Moreover, the 3D-printed outer robot shell promotes mechanical strength while the robot is moving. The optimal 50% porous outer shell is designed to protect the inner shell from continuous moving impact. Finite element simulations are also used to show that the 50% porosity of the outer shell significantly reduces the strain energy upon impact. Compared with a conventional single-layer design with a strain energy of 130 mJ, the double-layered shell with 50% porosity exhibits a reduced strain energy of 22.09 mJ. This double-layered design, which offers excellent weather resistance, high visible transparency, and effective radiative cooling, is promising for future applications in both land and water robot shells.