Chitosan-based electroconductive inks without chemical reaction for cost-effective and versatile 3D printing for electromagnetic interference (EMI) shielding and strain-sensing applications.

The burgeoning interest in biopolymer 3D printing arises from its capacity to meticulously engineer tailored, intricate structures, driven by the intrinsic benefits of biopolymers-renewability, chemical functionality, and biosafety. Nevertheless, the accessibility of economical and versatile 3D-printable biopolymer-based inks remains highly constrained. This study introduces an electroconductive ink for direct-ink-writing (DIW) 3D printing, distinguished by its straightforward preparation and commendable printability and material properties. The ink relies on chitosan as a binder, carbon fibers (CF) a low-cost electroactive filler, and silk fibroin (SF) a structural stabilizer. Freeform 3D printing manifests designated patterns of electroconductive strips embedded in an elastomer, actualizing effective strain sensors. The ink's high printability is demonstrated by printing complex geometries with porous, hollow, and overhanging structures without chemical or photoinitiated reactions or support baths. The composite is lightweight (density 0.29 ± 0.01 g/cm3), electroconductive (2.64 ± 0.06 S/cm), and inexpensive (20 USD/kg), with tensile strength of 20.77 ± 0.60 MPa and Young's modulus of 3.92 ± 0.06 GPa. 3D-printed structures exhibited outstanding electromagnetic interference (EMI) shielding effectiveness of 30-31 dB, with shielding of >99.9 % incident electromagnetic waves, showcasing significant electronic application potential. Thus, this study presents a novel, easily prepared, and highly effective biopolymer-based ink poised to advance the landscape of 3D printing technologies.

Novel 3D porous aerogels engineered at nano scale from cellulose nano fibers and curcumin: An effective treatment for chronic wounds.

Traditional cotton gauze derived from cellulose has many limitations in the processes of wound healing. To overcome these hassles, we used cellulose nanofibers (CNF) incorporated with curcumin for the fabrication of wound healing 3D porous aerogel. Cellulose nanofibers synthesized from plant waste are promising sustainable nanomaterials due to their biocompatibility and biodegradability. Ionic cross linking with sodium alginate was performed to maintain the mechanical strength. SEM results revealed highly porous architecture that effectively promoted wound healing, as a result of macro- and micro-porous architecture and curcumin. In-vitro drug release studies showed a slow and steady release pattern. The 3D porous nano bio aerogel with curcumin significantly promoted the migration of fibroblast cells and had excellent antimicrobial activity against pathogenic microorganisms. In-vivo studies showed angiogenesis without rejection or inflammation of the scaffold. From the observations, we can conclude that this novel 3D porous aerogel can be used to treat chronic wounds.

Ultra-fast heat dissipating aerogels derived from polyaniline anchored cellulose nanofibers as sustainable microwave absorbers.

Electromagnetic (EM) pollution is ubiquitous and has soared to a great extent in the past few decades. The use of plant sourced cellulose nanofibers to fabricate sustainable and high performance electromagnetic shielding materials is foreseen as a green solution by the electronics industry to address this unseen pollutant. In this view, we report a facile and environmentally benign strategy to synthesize ultra-light and highly conductive aerogels derived from cellulose nanofibers (CNF) decorated with polyaniline (PANI) via a simple in-situ polymerization and subsequent freeze drying process devoid of any volatile organic solvents. The obtained conductive aerogels exhibited density as low as 0.01925 g/cc with a maximum EMI shielding value -32 dB in X band region. These porous shields demonstrated strong microwave absorption behavior (95 %) with minimal reflection (5 %) coupled with high specific EMI SE value ∼1667 dB.cm3. g-1 which make these aerogels a potential candidate for use in telecommunication, military and defense applications.

Cellulose Nanofiber-Based Polyaniline Flexible Papers as Sustainable Microwave Absorbers in the X-Band.

A series of flexible, lightweight, and highly conductive cellulose nanopapers were fabricated through in situ polymerization of aniline monomer on to cellulose nanofibers with a rationale for attenuating electromagnetic radiations within 8.2-12.4 GHz (X band). The demonstrated paper exhibits good conductivity due to the formation of a continuous coating of polyaniline (PANI) over the cellulose nanofibers (CNF) during in situ polymerization, which is evident from scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The free hydroxyl groups on the surface of nanocellulose fibers promptly form intermolecular hydrogen bonding with PANI, which plays a vital role in shielding electromagnetic radiations and makes the cellulose nanopapers even more robust. These composite nanopapers exhibited an average shielding effectiveness of ca. -23 dB (>99% attenuation) at 8.2 GHz with 1 mm paper thickness. The fabricated papers exhibited an effective attenuation of electromagnetic waves by a predominant absorption mechanism (ca. 87%) rather than reflection (ca. 13%), which is highly desirable for the present-day telecommunication sector. Unlike metal-based shields, these demonstrated PANI/CNF papers have given a new platform for designing green microwave attenuators via an absorption mechanism. The prime novelty of the present study is that these robust PANI/CNF nanopapers have the ability to attenuate incoming microwave radiations to an extent that is 360% higher than the shielding effectiveness value reported in the previous literature. This makes them suitable for use in commercial electronic gadgets. This demonstrated work also opens up new avenues for using cellulose nanofibers as an effective substrate for fabricating conductive flexible papers using polyaniline. The direct current conductivity value of PANI/CNF nanopaper was 0.314 S/cm, which is one of the key requisites for the fabrication of efficient electromagnetic shields. Nevertheless, such nanopapers also open up an arena of applications such as electrodes for supercapacitors, separators for Li-S, Li-polymer batteries, and other freestanding flexible paper-based devices.