Advances in Additive Manufacturing of Polymer-Fused Deposition Modeling on Textiles: From 3D Printing to Innovative 4D Printing-A Review.

Technological advances and the development of new and advanced materials allow the transition from three-dimensional (3D) printing to the innovation of four-dimensional (4D) printing. 3D printing is the process of precisely creating objects with complex shapes by depositing superimposed layers of material. Current 3D printing technology allows two or more filaments of different polymeric materials to be placed, which, together with the development of intelligent materials that change shape over time or under the action of an external stimulus, allow us to innovate and move toward an emerging area of research, innovative 4D printing technology. 4D printing makes it possible to manufacture actuators and sensors for various technological applications. Its most significant development is currently in the manufacture of intelligent textiles. The potential of 4D printing lies in modular manufacturing, where fabric-printed material interaction enables the creation of bio-inspired and biomimetic devices. The central part of this review summarizes the effect of the primary external stimuli on 4D textile materials, followed by the leading applications. Shape memory polymers attract current and potential opportunities in the textile industry to develop smart clothing for protection against extreme environments, auxiliary prostheses, smart splints or orthoses to assist the muscles in their medical recovery, and comfort devices. In the future, intelligent textiles will perform much more demanding roles, thus envisioning the application fields of 4D printing in the next decade.

Adaptive IR- and Water-Gating Textiles Based on Shape Memory Fibers.

Thermoregulation is an essential function of the human body for adapting to the surrounding temperature. Stimuli-responsive smart textiles can provide effective protection of the human skin temperature from a continuously changing environment. Herein, we develop a smart textile based on shape memory polymer (SMP) fibers for adaptive regulation of IR and water transmission on human skin. An SMP textile is fabricated with hierarchical micro/nanoporous structures to enhance thermal insulation performance, and silver nanowires are coated on one side to provide asymmetric IR reflectivity and hydrophilicity. The porous SMP textile shows great tunability of thermal insulation and asymmetric wettability by deformation and recovery of the shape and structure in response to stimuli. The degree of thermal insulation is controlled by 65.7% of the original value, and the surface temperature of the SMP textile on a hot plate is successfully controlled in the IR images due to adaptive IR reflectivity. Additionally, the directional transportation of water droplets can be switched on/off according to the shape of the SMP textiles, which can be employed for sweat removal from the human skin. This IR- and water-gating smart textile can provide a feasible strategy for protecting the human skin from external environmental changes.

Deposition of Zinc Oxide on Different Polymer Textiles and Their Antibacterial Properties.

A surface modification of polyamide 6 (PA), polyethylene terephthalate (PET) and polypropylene (PP) textiles was performed using zinc oxide to obtain antibacterial layer. ZnO microrods were synthesized on ZnO nanoparticles (NPs) as a nucleus centers by chemical bath deposition (CBD) process. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) indicated that wurzite ZnO microrods were obtained on every sample. Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM) and Liquid Absorption Capacity (LAC) analysis indicate that the amount and structure of antibacterial layer is dependent on roughness and wettability of textile surface. The rougher and more hydrophilic is the material, the more ZnO were deposited. All studied textiles show significant bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). A possible mechanism and difference in sensitivity between Gram-negative and Gram-positive bacteria to ZnO is discussed. Considering that antibacterial activity of ZnO is caused by Reactive Oxygen Species (ROS) generation, an influence of surface to volume ratio and crystalline parameters is also discussed.