University of Wisconsin-Madison engineers have developed a "smart" piece of glass that recognizes images without any external power or circuits. The glass could potentially be used as a biometric lock, tuned to recognize only one person's face.
Erfan Khoram, Ang Chen, Dianjing Liu, Lei Ying, Qiqi Wang, Ming Yuan, and Zongfu Yu, "Nanophotonic media for artificial neural inference," Photon. Res. 7, 823-827 (2019)
We show optical waves passing through a nanophotonic medium can perform artificial neural computing. Complex information is encoded in the wavefront of an input light. The medium transforms the wavefront to realize sophisticated computing tasks such as image recognition. At the output, the optical energy is concentrated in well-defined locations, which, for example, can be interpreted as the identity of the object in the image. These computing media can be as small as tens of wavelengths and offer ultra-high computing density. They exploit subwavelength scatterers to realize complex input/output mapping beyond the capabilities of traditional nanophotonic devices.