Fig. 4

Three kinds of computation-enabled intelligent sensing using intelligent metasurface. a Conceptual illustration of nearly digital-computational-free intelligent sensing featuring its role in bridging the physical world and digital world. The range of the scene probed (marked in blue) is small in comparison to the whole scene in yellow, due to the use of metasurface-based linear data computation. b Programmable sensing system invented by Li et al. [122]. c The reprogrammable artificial intelligence machine (PAIM) based on an array of intelligent metasurfaces proposed by Liu et al. [219]. d All-optic reconstruction using diffractive networks proposed by Rahman and Ozcan [218]. e Conceptual illustration of hybrid-computing-based intelligent sensing, featuring its role in bridging the physical world and digital world. Here the hybrid computing consists of analog computing on the physical level and digital computing on the digital level. The analog computing for high-dimensional data reduction is achieved by the metasurface, while the digital computing for data postprocessing is done by using advanced signal processing techniques or artificial neural networks. f Computational metamaterial imager proposed by Hunt et al. [221]. g Intelligent EM metasurface imager and recognizer working at 2.4 GHz proposed by Li et al. [51] which has active and passive operational modes. For the passive mode, the intelligent metasurface is used to manipulate the ambient stray wireless signal already available in our daily lives. h The operational flowchart of intelligent metasurface sensor by Li et al. [51]. i Conceptual illustration of the hybrid-computing-based intelligent integrated sensing system, where the data acquisition on the physical level and data postprocessing on the digital level are integrated as a whole and are learned simultaneously. j–l Correspond to the schemes proposed by Li et al. [54], Hougne et al. [53] and Tseng et al. [232], respectively. Figures (b)–(d), (f)–(h) and (j)–(l) adapted with permission under a CC BY 4.0 license