Kojiro Uetani

Electrostatic flocking is applied to create an array of aligned carbon fibers from which an elastomeric thermal interface material (TIM) can be fabricated with a high through-plane thermal conductivity of 23.3 W/mK. A high thermal conductivity can be achieved with a significantly low filler level (13.2 wt%). As a result, this material retains the intrinsic properties of the matrix, i.e., elastomeric behavior.

We report the successful use of a high-speed blender in nanofibrillating never-dried pulp to cellulose nanofibers (CNFs) with a uniform diameter of 15-20 nm. Pulp treated for 30 min in a blender showed the same degree of fibrillation with less damage to the CNF compared with that treated in a grinder. Observing the process of nanofibrillation clarified that the straw-like pulp was fibrillated in a very characteristic way, by forming many "balloon-like structures". As the balloons extended to the

The thermal conductive properties, including the thermal diffusivity and resultant thermal conductivity, of nonwoven nanocellulose sheets were investigated by separately measuring the thermal diffusivity of the sheets in the in-plane and thickness directions with a periodic heating method. The cross-sectional area (or width) of the cellulose crystallites was the main determinant of the thermal conductive properties. Thus, the results strongly indicate that there is a crystallite size effect on p

In this review, we summarize the recent progress in thermal conductivity analysis of nanocellulose materials called cellulose nanopapers, and compare them with polymeric materials, including neat polymers, composites, and traditional paper. It is important to individually measure the in-plane and through-plane heat-conducting properties of two-dimensional planar materials, so steady-state and non-equilibrium methods, in particular the laser spot periodic heating radiation thermometry method, are

We developed flexible polymeric "heat-guiding materials" by simply drawing bacterial cellulose (BC) hydrogels to align the cellulose nanofibers and form "nanopapers" with anisotropic thermal conductivity. The in-plane anisotropy of thermal conductivity between the drawn and transverse directions increased as the draw ratio increased. For the drawn BC nanopapers, the coefficient of thermal expansion was found to be inversely correlated with the thermal diffusivity. We fabricated a planar spiral s

Thermally conductive and optically transparent flexible films were fabricated using nanocellulose skeletons with acrylic resin.

In this paper, we present the swelling dynamics of individual wood cellulose nanofibrils (CNFs) following solvent substitution into various organic solvents and drying, by employing the time dependence of the zeta potential (ζ). We succeeded in smoothly redispersing the coaggregating CNFs dried in solvents, including acetone, acetonitrile, DMSO, ethanol, and t-butanol into water. ζ-t plots of the redispersed CNFs measured in a 1 mM KCl solution indicated different values of Δζ (volume fraction o

The intrinsic birefringence of cellulose is one of the most fundamental optical parameters for analyzing and developing various cellulosic materials. However, the previously reported values greatly vary depending on the problems occurred due to the measured cellulose sample or method, and it is still a challenge to evaluate the intrinsic birefringence of cellulose using suitable cellulose samples and methodologies by taking account into the recent knowledge and techniques. Here, we estimated the

The relation between the fibril shapes and the self-organizing capacity was investigated by comparing the results of evaporation-induced self-assembly (EISA) in 2D (“coffee rings”) and 3D (spray-dried microparticles (MPs)) for rod-like and semi-flexible nanocelluloses. The rod-like tunicin nanowhiskers formed nematic alignment along the perimeter of coffee rings, and also formed curved discotic microparticles having nematic rings of width ∼300 nm by spray drying. On the other hand, the semi-flex

Chitin, a natural polysaccharide polymer, forms highly crystalline nanofibers and is expected to have sophisticated engineering applications. In particular, for development of next-generation heat-transfer and heat-insulating materials, analysis of the thermal conductivity is important, but the thermal conductivity properties of chitin nanofiber materials have not been reported. The thermal conductivity properties of chitin nanofiber materials are difficult to elucidate without excluding the eff

Abstract Heat dissipation has become increasingly important in electronics. Conventional convection cooling systems have significant material and dimensional constraints, and they have difficulty meeting the heat dissipation, miniaturization, and flexibility requirements of next-generation smart electronics. Here, we used kirigami (the traditional art of paper cutting) with a thermally conductive cellulose nanofiber film to propose a flexible cooling system through convective heat dissipation. B

We report a method for the semiquantitative structural analysis of highly anisotropic nanocolloids by means of their "coffee rings", which were readily formed via the evaporation of droplets of the cellulose nanocolloidal suspensions. The widths of the coffee rings reflected the effective aspect ratios and the conformation of the colloids in water, owing to the excluded volume effect. The theory developed here succeeded in estimating the relative length of the cellulose nanofibrils, which were o