Phase‐Manipulated Calcium Borate‐Based Multicolor Mechanoluminescence

ABSTRACT Multicolor mechanoluminescence (ML) materials have attracted growing attention for applications in anti‐counterfeiting, smart skin, wearable electronics, and structural health monitoring. However, their widespread implementation remains significantly hindered by the scarce available compositions and harsh preparation conditions—typically requiring temperatures above 1000°C and protective atmospheres. Here, a facile, low‐temperature, and atmosphere‐free synthesis of calcium borate‐based ML materials (Ca 2 B 2 O 5 and CaB 2 O 4 ) is achieved. The phase ratio of Ca 2 B 2 O 5 and CaB 2 O 4 is manipulated by adjusting the stoichiometric ratio of raw materials (H 3 BO 3 and CaO). The distinct tetrahedral and octahedral coordination of Mn 2+ in these phases gives rise to tunable ML emission spanning from green to orange (535–605 nm). When incorporated into polydimethylsiloxane (PDMS) elastomers, these materials exhibit remarkable multicolor ML suitable for multi‐level optical encryption and motion visualization. The encrypted information remains hidden under daylight or UV illumination can be deciphered only through ML activation, while the stress‐induced color variation enables real‐time monitoring of joint movement. This work not only establishes a versatile route for the design of low‐temperature, phase‐tunable ML materials but also reveals promising applications in next‐generation information security and intelligent motion‐sensing technologies.