Water-based 2D printing of magnetically active cellulose derivative nanocomposites

Improving Definition of Screen-Printed Functional Materials for Sensing Application

Screen printing is one of the most used techniques for developing printed electronics. It stands out for its simplicity, scalability, and effectivity. Specifically, the manufacturing of hybrid integrated circuits has promoted the development of the technique, and the photovoltaic industry has enhanced the printing process by developing high-performance metallization pastes and high-end screens. In recent years, fine lines of 50 μm or smaller are about to be adopted in mass production, and screen printing has to compete with digital printing techniques such as inkjet printing, which can reach narrower lines. In this sense, this work is focused on testing the printing resolution of a high-performance stainless-steel screen with commercial conductive inks and functional lab-made inks based on reduced graphene oxide using an interdigitated structure. We achieved electrically conductive functional patterns with a minimum printing resolution of 40 μm for all inks.

Mapping 3D Printability of Ionically Cross-Linked Cellulose Nanocrystal Inks: Architecting from Nano- to Macroscale Structures

Engineering the rheological properties of colloidal inks is one of the main challenges in achieving high-fidelity 3D printing. Herein, we provide a comprehensive study on the rheological behavior of inks based on cellulose nanocrystals (CNCs) in the presence of given salts to enable high-quality 3D printing. The rheological properties of the CNC suspensions are tailored by considering the nature of the electrolyte (i.e., 10 types of salts featuring different ion sizes, charge numbers, and inter- and intra-molecular interactions) at various concentrations (25-100 mM). A high printing fidelity is achieved in a narrow CNC and salt concentration range, significantly depending on the salt type. The structure-property relationship is explored in a "3D-printing" space (2D map), introducing a guideline for researchers active in this field. To further unravel the effect of salt type on morphological properties, CNC aerogels are developed by freeze-drying the printed structures. The results illustrate that enhancing viscoelastic properties render a denser structure featuring smaller pores.

Magnetic materials: a journey from finding north to an exciting printed future

The potential implications/applications of printing technologies are being recognized worldwide across different disciplines and industries. Printed magnetoactive smart materials, whose physical properties can be changed by the application of external magnetic fields, are an exclusive class of smart materials that are highly valuable due to their magnetically activated smart and/or multifunctional response. Such smart behavior allows, among others, high speed and low-cost wireless activation, fast response, and high controllability with no relevant limitations in design, shape, or dimensions. Nevertheless, the printing of magnetoactive materials is still in its infancy, and the design apparatus, the material set, and the fabrication procedures are far from their optimum features. Thus, this review presents the main concepts that allow interconnecting printing technologies with magnetoactive materials by discussing the advantages and disadvantages of this joint field, trying to highlight the scientific obstacles that still limit a wider application of these materials nowadays. Additionally, it discusses how these limitations could be overcome, together with an outlook of the remaining challenges in the emerging digitalization, Internet of Things, and Industry 4.0 paradigms. Finally, as magnetoactive materials will play a leading role in energy generation and management, the magnetic-based Green Deal is also addressed.