Progress in 4D printing of stimuli responsive materials

Smart materials are capable of sensing, memorizing, and changing their structure. Fabrication of smart materials established a modern-day technology called additive manufacturing (AM). However, non-uniform shrinkage, anisotropic behavior, and the 3D printing technique's static nature gave way to 4D printing with an additional 4th coordinate as a time for the dynamic design structures. This review article converges the progression, inclusions of intelligent materials, significant stimulus, multiple parameters, modeling of SMMs, filler interaction in SMCs, additive manufacturing processes applied for 4D printing, characterization techniques, and region of demand of 4D printing, as well as challenges and future scope in 4D printing.