Enhanced High Thermal Conductivity Cellulose Filaments via Hydrodynamic Focusing

Abstract

Nanocellulose is regarded as a green and renewable nanomaterial that has attracted increased attention. In this study, we demonstrate that nanocellulose materials can exhibit high thermal conductivity when their nanofibrils are highly aligned and bonded in the form of filaments. The thermal conductivity of individual filaments, consisting of highly aligned cellulose nanofibrils, fabricated by the flow-focusing method is measured in dried condition using a T-type measurement technique. The maximum thermal conductivity of the nanocellulose filaments obtained is 14.5 W/m-K, which is approximately five times higher than those of cellulose nanopaper and cellulose nanocrystals. Structural investigations suggest that the crystallinity of the filament remarkably influence their thermal conductivity. Smaller diameter filaments with higher crystallinity, that is, more internanofibril hydrogen bonds and less intrananofibril disorder, tend to have higher thermal conductivity. Temperature-dependence measurements also reveal that the filaments exhibit phonon transport at effective dimension between 2D and 3D.

Tunable thermal diffusivity of silk protein assemblies based on their structural control and photo-induced chemical cross-linking

“…Recent studies have revealed that bulk lms comprising structurally regular biopolymers, such as nanocellulose, lamentous viruses, and designed tandem-repeat proteins, are promising thermally conductive materials. 19,20,[23][24][25][26][27][28][29][30] The chemical cross-linking of SF materials has recently been used in addition to physical cross-linking, through the formation of crystalline antiparallel b-sheets, to improve and/or pioneer physicochemical properties and functions. With relatively high amounts of Tyr residues in SF (Tyr: 5.3 mol% Gly: 45.9 mol%, Ala: 30.3 mol%, Ser: 12.1 mol%, and Val: 1.8 mol%), 31,32 it was reported that the oxidation of adjacent Tyr residues by horseradish peroxidase or ultraviolet (UV) light irradiation resulted in chemically cross-linked SF by the effective formation of dityrosine.…”

“…Recent studies have revealed that bulk films comprising structurally regular biopolymers, such as nanocellulose, filamentous viruses, and designed tandem-repeat proteins, are promising thermally conductive materials. 19,20,23–30…”