Flexible and stretchable thermoresponsive display for multifunctional device applications

Abstract

Metal–organic frameworks (MOFs) have been recognized vastly as stimuli-responsive materials owing to their extreme sensitivity toward the stimuli that make them flawless nominees for multifunctional device applications. However, MOFs are often oversensitive toward moisture, which significantly affects their stable responses and reproducibility. Herein, a MOF–polymer display (i.e., copper-based MOF with polydimethylsiloxane) is developed that exhibits high sensitivity toward temperature changes without getting affected by moisture. In response to the thermal gradient, the display exhibits the change in color from sky blue to dark blue when the temperature varies from 30 to 100 ºC, which is attributed to the second-order phase transition within the time interval 40 s and reversible in 60 s. To provide insights on the mechanism, ex situ UV–vis and temperature-dependent operando X-day diffraction are conducted, which unveils that the color change in the display is associated with reversible contraction/expansion of the unit cell parameters. In addition to that, the thermoresponse of the display remains unaffected under mechanical deformations, which indicates that the color display is mechanically and thermally stable. The as-developed color display is mechanically robust and highly sensitive toward temperature change; it can be utilized as the color indicator in signaling temperature rise in smart mobiles or laptops during discharging to keep the user safe or applications in augmented intelligence.