Lignin‐Based Materials for Additive Manufacturing: Chemistry, Processing, Structures, Properties, and Applications

Abstract

The utilization of lignin, the most abundant aromatic biomass component, is at the forefront of sustainable engineering, energy, and environment research, where its abundance and low‐cost features enable widespread application. Constructing lignin into material parts with controlled and desired macro‐ and microstructures and properties via additive manufacturing has been recognized as a promising technology and paves the way to the practical application of lignin. Considering the rapid development and significant progress recently achieved in this field, a comprehensive and critical review and outlook on three‐dimensional (3D) printing of lignin is highly desirable. This article fulfils this demand with an overview on the structure of lignin and presents the state‐of‐the‐art of 3D printing of pristine lignin and lignin‐based composites, and highlights the key challenges. It is attempted to deliver better fundamental understanding of the impacts of morphology, microstructure, physical, chemical, and biological modifications, and composition/hybrids on the rheological behavior of lignin/polymer blends, as well as, on the mechanical, physical, and chemical performance of the 3D printed lignin‐based materials. The main points toward future developments involve hybrid manufacturing, in situ polymerization, and surface tension or energy driven molecular segregation are also elaborated and discussed to promote the high‐value utilization of lignin.

Copolymerizing Lignin for Tuned Properties of 3D-Printed PEG-Based Photopolymers

“…We attribute this issue to a decrease in the efficiency of layer bonding. This is caused by the high absorption of UV light by lignin at this concentration, which not only inhibits photopolymerization but also interferes with lignin’s radical scavenging properties. ,, High UV light absorption is also confirmed by the UV–vis absorption spectra (Figure a).…”

“…Thus, lignin improves the resistance and fracture toughness of the copolymers studied. 4,61,62 This property is limited beyond 5.0 w/v % loading, probably because of the higher cross-linking density that is also visible in the high tensile Young's modulus value. Given that polyPEGDA, unlike other elastomers, is a highly brittle polymer with a low value of Young's modulus, the mechanical "optimum" can be found for a composition with a 2.0 w/v % content of the methacrylated lignin.…”

“…However, only a few reports utilized lignin in 3D printing due to its low solubility or incompatibility with the matrix. , 3D printing (additive manufacturing) is an automated fabrication process of creating three-dimensional objects by adding material layer-by-layer . It enables the production of custom objects from digital designs, eliminating traditional subtractive methods such as cutting, masking, or molding.…”

3D Printed Pharmaceutical Systems for Personalized Treatment in Metabolic Syndrome

“…The major types of 3D printing techniques used for pharmaceutical product design include inkjet 3D printing [53,54], including advanced electrohydrodynamic inkjet 3D printing technology [55], binder jet 3D printing [56][57][58], direct ink writing (DIW) [59][60][61], fused deposition modeling (FDM) [62][63][64], pressure-assisted micro syringes (PAM) [51,65], and laser-based 3D printing techniques, which includes stereolithographic (SLA) [66,67] and selective laser sintering (SLS) [68,69]. The various types of 3D printing techniques, parameters, and material choices are shown in Table 2.…”

“…Similarly, the direct ink writing (DIW) technique, which has been shown efficient to create functionalized lignin particles, could exhibit tunable antioxidant properties. This aspect is crucial to develop antimicrobial and antibacterial pharmacological treatments [59,60].…”