Published papers

© 2018 IEEE. Nanoscale thermometry is important for the thermal design of micro and nanodevices. In the measurement, a non-contact, non-destructive method is effective. Our method provides a nanoscale infrared thermometry with a tapered highly efficient near-field fiber probe.

© 2018 IEEE. A novel plastic based microfluidic chip for the optical diffusion sensor using the laser-induced dielectrophoresis is designed and fabricated. The diffusion signal of the first-order diffracted light was detected by using our proposed microfluidic chip.

© 2018 IEEE. An in-vitro method for temperature mapping of a single cell using fluorescence in near-field and a membrane window is developed. In this paper, we report analytical results which indicate the feasibility of our method.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. In the present study, we propose a new approach for coding two-dimensional patterns (spatial information or images) into mode spectra of a silicon microcavity. Electric field distributions associated with each cavity mode generated by the microcavity provide a basis (dictionary) for image encoding. The cavity is covered with a layer of phase-change material (Ge2Sb2Te5; GST), which enables the electric field distribution to be memorized and the images to be encoded into absorption spectra via the difference in the refractive index between the crystalline and amorphous phases. In numerical simulations, a clear modification of the absorption spectra of the GST layer upon partial crystallization was demonstrated. We fabricated silicon microcavities covered with a GST layer and confirmed that spectral features originating from individual cavity modes can be greatly modified upon phase change.

© 2018 The Authors Diffusion sensors for nano-sized materials dispersed in a solution are promising tools for investigating intermolecular interactions, which is an important task in a wide range of industrial and biomedical fields, such as the development of therapeutic products and diagnostic tools. For the development of the sensor applicable to point-of-care testing, an optofluidic sensor was proposed. The proposed sensor realizes a simple measurement in a short time using microscale manipulation by interferometrically-induced dielectrophoresis and optical detection. In this paper, the applicability of the proposed sensor to distinguish nanoscale differences in size was confirmed by measurements on a solution containing size-certified plain nano-beads (51 nm, 100 nm, 203 nm, 216 nm and 240 nm) with evaluating the uncertainties of the proposed sensor. Furthermore, measurements using 200-nm beads coated with functional groups (NH2 and biotin) and proteins (streptavidin and bovine serum albumin) demonstrated the applicability to the investigation of intermolecular interactions.

© 2019 IEEE. A novel nanoparticle sorting technique using the laser-induced dielectrophoresis (LIDEP) and phase modulated interference has been developed. In this paper, a proposed method of nanoparticle sorting and fabrication of microfluidic device are reported, and the validity of a method is discussed.

© 2019 IEEE. A large stroke electrothermal MEMS actuator with small device footprint and low driving voltage has been proposed for motion tracking blood flow measurement. This paper reports this kirigami-inspired device design and simulation results of the proposed actuator.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Endoscopic autofluorescence lifetime imaging is a promising technique for making quantitative and non-invasive diagnoses of abnormal tissue. However, motion artifacts caused by vibration in the direction perpendicular to the tissue surface in a body makes clinical diagnosis difficult. Thus, this paper proposes a robust autofluorescence lifetime sensing technique with a lens tracking system based on a laser beam spot analysis. Our optical setup can be easily mounted on the head of an endoscope. The variation in distance between the optical system and the target surface is tracked by the change in the spot size of the laser beam captured by the camera, and the lens actuator is feedback-controlled to suppress motion artifacts. The experimental results show that, when using a lens tracking system, the standard deviation of fluorescence lifetime is dramatically reduced. Furthermore, the validity of the proposed method is experimentally confirmed by using a bio-mimicking phantom that replicates the shape, optical parameters, and chemical component distribution of the cancerous tissue.

© 2020 Optical Society of America under. This paper proposes an electrothermally-actuated circular pyramidal kirigami microscanner with a millimeter-range low-power lens drive for endoscopic biomedical applications. A variation of Japanese origami art, kirigami involves creation of out-of-plane structures by paper cutting and folding. The proposed microscanner is composed of freestanding kirigami film on which the spiral-curved thermal bimorphs are strategically placed. The kirigami microscanner is electrothermally transformed into an out-of-plane circular multistep pyramid by Joule heating. The circular pyramidal kirigami microscanner on a small footprint of 4.5 mm 4.5 mm was fabricated by microelectromechanical system processes. A large four-step pyramidal actuation was successfully demonstrated, and a large 1.1-mm lens travel range at only 128 mW was achieved.

© 2020 by the authors. Large-displacement microelectromechanical system (MEMS) scanners are in high demand for a wide variety of optical applications. Kirigami, a traditional Japanese art of paper cutting and folding, is a promising engineering method for creating out-of-plane structures. This paper explores the feasibility and potential of a kirigami-inspired electrothermal MEMS scanner, which achieves large vertical displacement by out-of-plane film actuation. The proposed scanner is composed of film materials suitable for electrothermal self-reconfigurable folding and unfolding, and microscale film cuttings are strategically placed to generate large displacement. The freestanding electrothermal kirigami film with a 2 mm diameter and high fill factor is completely fabricated by careful stress control in the MEMS process. A 200 μm vertical displacement with 131 mW and a 20 Hz responsive frequency is experimentally demonstrated as a unique function of electrothermal kirigami film. The proposed design, fabrication process, and experimental test validate the proposed scanner's feasibility and potential for large-displacement scanning with a high fill factor.