Ultrasound-activated luminescence with color tunability enabled by mechanoluminescent colloids and perovskite quantum dots.

Ultrasound represents a wireless and non-contact route for energy delivery and device control, owing to its ability to propagate and focus in various mediums including biological tissue. Specifically, ultrasound-activated mechanoluminescence from a colloidal suspension of mechanoluminescent (ML) nanocrystals offers a wireless means to remotely control a light source, such as wirelessly addressing a multicolor display. However, the limited color purity and tunability, as well as the large sizes of conventional ML materials prevent their use in an ultrasound-mediated flexible color display. Here, we apply a biomineral-inspired suppressed dissolution approach to synthesize ML colloids with bright blue emission under ultrasound and small sizes down to 20 nm. In addition, we leverage the bandgap engineering strategy of all-inorganic perovskite quantum dots (PQDs) to achieve wavelength tunability of the mechanoluminescence of ML colloid/PQD composites. Remarkably, the ultrasound-activated emission of the ML colloid/PQD composites exhibits a highly saturated color gamut covering the entire visible spectrum. Based on these advantages, we assembled a pixel array composed of different ML colloid/PQD composites in a silicone elastomer and demonstrated the proof-of-concept of a flexible and wireless multicolor display with each pixel individually addressed by scanning focused ultrasound.