Tokyo Institute of Technology · Materials Science
Professor Junko Morikawa's research lab specializes in the advanced characterization of thermal, mechanical, and optical properties at the micro- and nanoscale, with a focus on developing and applying innovative thermal wave analysis techniques. The lab investigates thermal transport in functional materials such as polyimide thin films, doped single crystals, laser-structured sapphire, and biomimetic nanostructures like cicada wings, emphasizing anisotropy and local property variations. A key innovation is the application of temperature wave analysis (TWA) and Fourier transform thermal analysis to measure thermal diffusivity and heat capacity with high spatial and frequency resolution, enabling insights into phonon scattering and material heterogeneity.
Figures are computed from collected data and may differ slightly.
The heat transport properties of aromatic polyimide thin films have become more important in the use for the electric insulation in the microelectronic devices with highly integrated circuits. The various kinds of measuring methods have been applied to obtain the anisotropic thermal conductivity and thermal diffusivity of thin films, however, if the specimens are soft and transparent, the conventional methodology requires highly advanced technology in preparing the specimens for the measurement
Thermal diffusivity and thermal conductivity of single crystals of Nd3+ doped GdVO4, YVO4, LuVO4, and Y3Al5O12 are precisely measured over a wide range of doping concentration from 0.5to15at.% by temperature wave analysis. Thermal diffusivity serves as the most sensitive parameter to detect the effect of doping on thermal properties, where Nd3+ doped GdVO4 exhibits a decrease in thermal diffusivity (it has changed about 20% in their values in the c axis) but an increase in heat capacity (only 1.
Temperature diffusivity of laser micro-structured regions in sapphire is determined by a temperature wave method with a lateral resolution reduced to ~10 microm using a directly sputtered micro-sensor and heater. A record high reduction of the temperature diffusivity of sapphire by 12% from its (1.26+/-0.02) x 10(-5)m(2)/s in-bulk value inside the femtosecond laser-structured volumes is determined; in a BK7 glass (~4.8x10(-7) m(2)/s), a 2% decrease of the thermal diffusivity has been observed. O
Inter-related mechanical, thermal, and optical macroscopic properties of biomaterials are defined at the nanoscale by their constituent structures and patterns, which underpin complex functions of an entire bio-object. Here, the temperature diffusivity of a cicada (Cyclochila australasiae) wing with nanotextured surfaces was measured using two complementary techniques: a direct contact method and IR imaging. The 4-6-μm-thick wing section was shown to have a thermal diffusivity of α⊥ = (0.71 ± 0.
The high-order harmonics of temperature wave were detected in a thin film by inputting a square pulse train with a variable duty factor to generate temperature modulation. In Fourier analysis, the harmonics were observed up to the 42 th order and the mathematical rule was experimentally confirmed. This principle was applied to a technique called “Fourier transform thermal analysis,” which made it possible to determine simultaneously thermal diffusivity and heat capacity per unit volume as a func
Hyperspectral imaging is now augmented by separation of the birefringence, dichroism and orientation function at the same wavelength and pixel by combining Malus and Beer–Lambert laws.
Domestic (<i>Bombyx mori</i>) and wild (<i>Antheraea pernyi</i>) silk fibers were characterised over a wide spectral range from THz 8 cm -1 ( λ = 1.25 mm, f = 0.24 THz) to deep-UV 50 × 10 3 cm - 1 ( λ = 200 nm, f = 1500 THz) wavelengths or over a 12.6 octave frequency range. Spectral features at β-sheet, α-coil and amorphous fibroin were analysed at different spectral ranges. Single fiber cross sections at mid-IR were used to determine spatial distribution of different silk constituents and reve
Grid polarisers 3D-printed out of commercial acrilic resin were tested for the polariser function and showed spectral regions where the dichroic ratio D-R > 1 and < 1 implying importance of molecular and/or stress induced anisotropy. Metal-coated 3D-printed THz optical elements can find a range of applications in intensity and polarization control of IR-THz beams. The used 3D printing method allows for fabrication of an arbitrary high aspect ratio grid polarisers. Polarization analysis of
A non-contact determination of thermal diffusivity and spatial distribution of temperature on tens-of-micrometers scale is demonstrated by thermal imaging. Temperature localization and a heat flow have been in situ monitored with ∼ 10 ms temporal resolution in Kapton polymer films structured by femtosecond laser pulses. The structured regions can localize temperature and create strong thermal gradients of few degrees over tens-of-micrometers (∼ 0.1 K/μm). This is used to induce an anisotropy in
E-beam exposure unzips beta-sheets in crystalline domains of silk fibroin and makes it water-soluble, enabling its usage as an aqueous-based electron beam lithography resist.
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