Water-triggered visible and infrared light reversible switch using nanowires-covered micropores superhydrophilic surfaces

Materials with switchable optical properties play a vital role in widespread applications such as communication, camouflage, thermoregulation and imaging. Typically, the optical switching is triggered by inputting thermal, voltage, UV light, etc. However, these inputs are usually required ready access to extra energy, which can limit its use for practical applications. Herein, a nanowire-covered micropores structured glass fabricated via femtosecond laser direct writing technology where optical properties can be switched depending only on wetting/drying of the superhydrophilic surface. The optical visibility of this laser treated glass (LTG) can be reversibly converted between opaque and clear modes with both visible and infrared light. In the wetted state, LTG shows high visible transparency and relatively low infrared emission. On the other hand, a dried LTG sample blocks light, blurs restored and the infrared emission is increased because of the rough surface. The corresponding mechanism of dual-reversible transition of visible and infrared light is also discussed. According to the variation in optical properties during the switching process, it demonstrated that the LTG could act as the projection screen in the dry state. Interestingly, we experimentally verified that the role of both high visible transmittance for viewing glass and the controllable infrared emissivity (ε) for encryption in the wet state. Meanwhile, it exhibits excellent cycling stability for controllable switching performances. This facile dual switchable visible and infrared wavelength material will widen the vision for a broad range of optical applications.