Research projects

限界値の定理では、単独で振る舞う個体の最適な採餌行動を予測している。しかし、実際には多くの動物種の採餌行動が、同種他個体との個体間相互作用に左右されることが知られている。海洋での採餌と巣のある島での雛への給餌を繰り返す海鳥であるオオミズナギドリをモデル種として、バイオロギングとリアルタイム生理情報収集システムを駆使して、時空間的に変動する海洋環境の中でいかにして効率的な採餌を達成し、同じ餌資源を巡る同種他個体がいる状況でいかに振る舞っているのかを明らかにする。

本研究では、動物の体に計測機器を取り付けるバイオロギングの手法を用いて、海洋高次捕食動物（海生哺乳類、海鳥、ウミガメ類、大型魚類）が人為起源の海洋環境ストレッサーにどのような影響を受けているかを調べる。代表的な5種のストレッサー（水温上昇、海氷減少、貧酸素化、海洋汚染、海中騒音）に対し、研究にふさわしい動物を選んで機器を取り付け、行動、生理、周囲の環境を詳細に計測し、解析する。

術中顔面神経持続モニタリングとして、側頭骨内に留置する最適な刺激電極形態を検討し、刺激電極のプロトタイプを作成する。また、術中顔面神経反応により術後顔面神経機能を予測するカットオフ値の制定を目指す。さらに、蝸牛神経モニタリングのための蝸牛内刺激電極からの至適刺激条件を検討し、術中eDNAP反応と術後人工内耳装用閾値との関連を検討する。

本研究では、海鳥に取り付け可能なピトー管型の防水流速センサによる計測システムを創成する。研究開発したシステムを利用し、GPSから得られる対地速度と組み合わせることで、バイオロギングによる実際の海鳥の飛行中の対地速度ベクトル、対気速度、風速ベクトルを明らかにすることを目指す。

本研究では、普及の決め手に欠けるフレキシブルエレクトロニクスの現状を打破する「次世代のフレキシブルエレクトロニクスの基盤技術」の確立を目的として、３つの研究項目、A:「極薄Si半導体素子とフレキシブルエレクトロニクスの融合」、B:「レーザー誘起グラフェンによる金属を用いない配線・センサ・アクチュエータ形成技術」、C:「Auxetic Structureによる伸張性と強度を両立したシート型フレキシブルデバイスの実現」を設定し、次世代のフレキシブルエレクトロニクスのための基盤技術の創成に取り組む。

本研究は、MEMSとサンプリングモアレ法を組み合わせることにより、生物の運動に伴う力のベクトルを高力分解能かつ高時間分解能で計測でき、かつ作りやすく使いやすく普及しやすい力センサプラットフォームを創成する。具体的には、人の歩行時の足裏反力分布をフォースプレートアレイで、海洋生物の遊泳時の対水速度ベクトルを流速センサで、昆虫の羽ばたき飛翔時の飛翔力を6軸センサプローブで計測することを目指す。

In this research, we developed a fabrication method of a three-dimensional (3D) microstructure via photolithography, which is one of the basic Micro Electro Mechanical Systems (MEMS) processes. We realized such 3D photolithography based on refractive-indices changes of UV curable material during photo-polymerization. When such material is used, UV light ray receives refraction effect during exposure, thus changes the light path and forms 3D photo-polymerized structure. Polyethylene Glycol Diacrylate (PEGDA), which is one of the common UV curable and biocompatible materials, was used in the fabrication process. We demonstrated the 3D lithography by fabricating PEGDA microneedle array, micro suction cup array, and so on.

In this project, a triaxial MEMS force sensing cantilever was studied. The sensor is equipped with a piezoresistor for force sensing at the root of the cantilever so that a quantitative mechanical stimuli could be applied to biological cells. The MEMS cantilever was made from an SOI wafer. A piezoresistive layer was formed by thermal diffusion on the surface of either cantilever root or the sidewall of the beam structure so that the corresponding three dimensional forces can be detected simultaneously. The resolution of the measurable force was as small as 1 uN for all the three directional forces, and the triaxial force could be independently measured with the device.

We have developed a microfluidic channel that can be combined with commercially available culture inserts with collagen vitrigel membranes, and have succeeded in reproducing the mechanical stimulation associated with blood flow in vivo by applying a flow of culture medium to cells cultured on vitrigel membranes. The morphology of co-cultured tissues consisting of myofibers and vascular endothelial cells was confirmed to be changed by the flow of culture medium. Furthermore, we found that the flow stimulation changed functions of co-cultured tissues consisting of hepatocytes and vascular endothelial cells, such as albumin production and albumin transfer to the flow, indicating that the proposed microfluidic system is useful as a model of vascular structure.

Sea animals such as sea turtles and penguins are adept at utilizing ocean currents to reduce the energy consumption of their swimming movements. A crucial factor in evaluating this utilization is the relative waterflow velocity, but actual measurements in sea animals are extremely limited. In this study, we have developed a Pitot tube-type waterflow velocity sensor that can be attached to sea animals. This sensor comprises a membrane structure attached to a dynamic inlet and a static inlet, filled with incompressible oil, and a differential pressure sensor element. Furthermore, the fabricated waterflow velocity sensor was integrated into a biologging sensor system to measure the relative water velocity of sea turtles and penguins.

Using an ultra-precision 3D printer, we designed and fabricated a force plate structure, and constructed a force plate system by combining the prototype force plate structure with a laser displacement meter. In addition, calibration experiments of the force plate against the force and evaluation of the resonance frequency were conducted. Theoretical construction and demonstration experiments were conducted on the positional error of the response due to the misalignment of the spot positions of the force plate structure and laser displacement meter. Using the force plate system, we measured the ground reaction force (GRF) of a fruit fly while walking, and measured the GRF equivalent to the body weight as a response.

In this study, we aim to realize MEMS optical metamaterials with significantly modulated optical properties by utilizing kirigami structures. Traditional methods for dynamically modulating the properties of optical metamaterials have involved three-dimensional shape changes of optical resonance structures and changes in the spacing of resonators through stretching flexible substrates. However, these methods have limitations and do not provide the modulation functions required for practical devices. Therefore, by integrating kirigami structures, which allow for high degrees of freedom in creating three-dimensional structures from two-dimensional planes, we aim to eliminate structural constraints and establish the foundational technology for realizing optical metamaterials with vastly enhanced modulation capabilities.

We analyzed approximately 400 cases of vestibular schwannomas and found that many cases of acute sensorineural hearing loss had U-shaped audiograms, especially in those under 40 years of age. In addition, we found that many elderly patients with vestibular schwannomas had a left-right difference in the high-frequency range. We also demonstrated the possibility of hearing restoration from retro-cochlear hearing loss by utilizing a wave I of the auditory brainstem response during surgery. Furthermore, we achieved the world's highest hearing preservation surgery and established a new monitoring method using intracochlear stimulating electrodes. On the other hand, the usefulness of the cochlear electrogram was limited, and the superiority of the auditory brainstem response as auditory monitoring became clear.

To realize vibrational circularly polarized light dichromatic spectroscopy in the THz frequency band, a MEMS tunable metamaterial was formed with a three-dimensional chiral optical resonator structure that resonates strongly with circularly polarized light. In order to achieve the goal, the MEMS tunable metamaterial needs to be deformed significantly, so we focused on the generation of a stable large deformation method, which has been a problem in the past. In order to realize a stable large deformation method, we focused on the elimination of instability from the deformation method and the excellent deformation characteristics of silicon, and came up with a driving method that mechanically pulls up the helical structure fabricated on a silicon substrate. We designed and fabricated a structure that enables large deformation, verified the amount and shape of deformation by the mechanical driving method, and clarified the response of the fabricated structure by calculation.

The developed acoustic filter consists of a number of spherical Helmholtz resonators (HRs), which are placed at the in-plane vertices of a regular polygon. A simulation result reveals that this uniform arrangement of HRs improves the silencing effect because the uniform applied waves emitted from the HRs act as canceling waves to the cross-section of the short hole. The total pressure emitted from the HRs is equal regardless of the number of HRs connected to the hole. Therefore, the arrangement of HRs is essential for realizing a planar notch filter. Simulated transmittance spectra demonstrated that the depth of the dip in the transmittance increases with the number of uniformly arranged HRs. It is confirmed that the experimental results with the fabricated filters, which consist of between one and six HRs, agrees with the simulated transmittance spectra.