机械变色材料提供响应机械应力的光学变化,并在广泛的潜在应用,如应变传感,结构健康监测,和加密。3D打印等先进制造可以制造复杂的图案和几何形状。在这项工作中,可拉伸的机械变色材料类别,在施加张力时提供视觉颜色变化,即,染料,聚合物分散液晶,液晶弹性体,纤维素纳米晶体,光子纳米结构,水凝胶,并回顾了混合系统(其他类别的组合)。对于每个班级,合成和加工,以及颜色变化的机理进行了讨论。要启用跨类的材料选择,比较了不同类别材料的机械变色敏感性。光子系统表现出高的机械变色灵敏度(Δnm/%应变),大动态颜色范围,和快速可逆性。Further,可以使用简单的力学模型来预测力学行为。已经实现了具有宽范围的机械性能(弹性模量)的光子系统。在光子系统中添加染料扩大了动态范围,即,有光学变化的应变。对于需要不可逆颜色变化的应用,可以配制基于染料的系统或液晶弹性体系统。虽然已经证明了许多有前途的应用,大规模制造均匀的颜色仍然是一个挑战。需要标准化的表征方法来将材料转化为实际应用。机械变色材料的可持续性也是一个重要的考虑因素。
Mechanochromic materials provide optical changes in response to mechanical stress and are of interest in a wide range of potential applications such as strain sensing, structural health monitoring, and encryption. Advanced manufacturing such as 3D printing enables the fabrication of complex patterns and geometries. In this work, classes of stretchable mechanochromic materials that provide visual color changes when tension is applied, namely, dyes, polymer dispersed liquid crystals, liquid crystal elastomers, cellulose nanocrystals, photonic nanostructures, hydrogels, and hybrid systems (combinations of other classes) are reviewed. For each class, synthesis and processing, as well as the mechanism of color change are discussed. To enable materials selection across the classes, the mechanochromic sensitivity of the different classes of materials are compared. Photonic systems demonstrate high mechanochromic sensitivity (Δnm/% strain), large dynamic color range, and rapid reversibility. Further, the mechanochromic behavior can be predicted using a simple mechanical model. Photonic systems with a wide range of mechanical properties (elastic modulus) have been achieved. The addition of dyes to photonic systems has broadened the dynamic range, i.e., the strain over which there is an optical change. For applications in which irreversible color change is desired, dye-based systems or liquid crystal elastomer systems can be formulated. While many promising applications have been demonstrated, manufacturing uniform color on a large scale remains a challenge. Standardized characterization methods are needed to translate materials to practical applications. The sustainability of mechanochromic materials is also an important consideration.