Direct Ink Writing: A 3D Printing Technology for Diverse Materials

Abstract

Additive manufacturing (AM) has gained significant attention due to its ability to drive technological development as a sustainable, flexible, and customizable manufacturing scheme. Among the various AM techniques, direct ink writing (DIW) has emerged as the most versatile 3D printing technique for the broadest range of materials. DIW allows printing of practically any material, as long as the precursor ink can be engineered to demonstrate appropriate rheological behavior. This technique acts as a unique pathway to introduce design freedom, multifunctionality, and stability simultaneously into its printed structures. Here, a comprehensive review of DIW of complex 3D structures from various materials, including polymers, ceramics, glass, cement, graphene, metals, and their combinations through multimaterial printing is presented. The review begins with an overview of the fundamentals of ink rheology, followed by an in‐depth discussion of the various methods to tailor the ink for DIW of different classes of materials. Then, the diverse applications of DIW ranging from electronics to food to biomedical industries are discussed. Finally, the current challenges and limitations of this technique are highlighted, followed by its prospects as a guideline toward possible futuristic innovations.

Advances in 3D Gel Printing for Enzyme Immobilization

“…Though less common than its use for enzyme entrapment, material extrusion by DIW is certainly compatible with post-printing enzyme immobilization. DIW can be used to print essentially any material as long as the precursor ink is formulated to possess favorable rheological behavior [ 33 ]. Dong et al [ 57 ] printed silver nanoparticles directly onto a printed circuit board (PCB), which was later coated with a Nafion layer to assist the co-immobilization of lactate oxidase in a bovine serum albumin matrix for the construction of an electrochemical lactate biosensor.…”

“…As previously mentioned, material extrusion by DIW is able to print practically any material type as long as proper rheology requirements are met with “ink” formulation [ 33 ]. A fundamental operational requirement for DIW is the ability to extrude a continuous, coherent filament which, upon deposition, is able to support its own weight and preserve the printed structure.…”

“…Currently, most multi-enzyme cascades are created either by post-printing multi-step enzyme immobilization combined with masking procedures for patterning or through the change of printing ink or resins while the printer is paused; both are laborious procedures. Imminent solutions to this problem are to increase accessibility of the aforementioned MJP and accelerate the adoption of other multi-material printing techniques, such as the use of core-shell co-axial nozzles or multi-nozzle arrays in DIW [ 33 ]. We expect these, and even more advanced techniques, to promote extensive future exploration of biomimetic enzyme cascades that employ diverse enzyme selections—such cascades are the essence of life.…”

“…The process then continues to stack materials layer-by-layer until the whole object is formed. Based on raw material physical properties, two different mechanisms for ME are followed: (1) fused deposition modeling (FDM) and (2) direct ink writing (DIW) [ 33 , 34 , 35 , 36 ]. FDM involves the melting and deposition of thermoplastics and therefore requires heating the print head.…”

Tissue Adhesive, Conductive, and Injectable Cellulose Hydrogel Ink for On-Skin Direct Writing of Electronics

“…Owing to their deformable characteristics, flexible electronics can be used as next-generation electronic devices that contact the human skin instead of conventional hard electronic devices [ 14 , 15 ]. In recent studies, a strategy for printing inexpensive and flexible electronic materials called electronic tattoos or epidermal electronics to directly write on the skin was evaluated [ 16 , 17 ]. Printed electronics on the skin can be used in various fields, such as light-emitting diodes (LEDs) [ 18 ], sensors [ 19 , 20 ], and transistors [ 21 ].…”