Chemical Engineering Journal, Vol.366, 264-304, 2019
Breakthrough in the printing tactics for stimuli-responsive materials: 4D printing
The idea of 3D printing ever since 1980' s has agitated the research domains challenging the conventional techniques with its inordinate efficiency in the utility of material, superior surface resolution and single step production which are applied in biomedical, electronics, self-healing and most prominently in biomimetic applications. However, this additive technique could not be controlled to produce intricate structure, to suppress strain controlled dimensional change, and anisotropic behavior. This complexity and inflexible design that had barricaded their dimension were vanquished by 4D printing with its dynamic structures. The fourth dimension conferred vitality to the design using stimulus to drive the transformation in smart materials (Shape Memory Effect or SME). Smart materials are environmentally sensitive materials comprising of polymers, alloys, hydrogels, ceramics and composites, activated by heat (pre-strain), water (absorption), electromagnetic radiations (Infrared, IR), magnetic field, ohmic parameters (current and voltage), solvent and pH. 4D printing attempts to counterfeit natural processes (flower blooming, leaf cirrus (tendrils), and sunflower movement) in drug delivery, wearable electronics, fashion wares, self-transmuting origami structures, sensors and other engineering applications. This review engulfs the evolution, burgeoning advancements and life cycle prediction of 4D printing with focusing on the smart materials and associated features like stimuli response along with future scope and challenges.