Published papers

An electro-conjugate fluid (ECF) is a type of dielectric functional fluid, which generates a powerful flow when a high direct-current voltage is applied. To date, ECF flow has been used in mechanical, chemical and biomedical applications because of its outstanding properties as a micro-pressure source for compact fluid-driven systems. However, the mechanism of ECF flow generation is not clarified and a basic understanding of ECF flow is required to progress ECF applications. We have developed the basic understanding of ECF flow generation through mathematical modeling, and have investigated electrical parameters theoretically. We have clarified microscopically the mechanism for ECF flow generation. We have proven the adequacy of the developed basic understanding by comparing visualized and computed flow characteristics. Furthermore, we have clarified the mechanism for ECF flow generation by comparing ionic transfer and ECF flow.

Tactile sensation is one type of valuable feedback in evaluating a product. Conventionally, sensory evaluation is used to get direct subjective responses from the consumers, in order to improve the product's quality. However, this method is a time-consuming and costly process. Therefore, this paper proposes a novel tactile evaluation system that can give tactile feedback from a sensor's output. The main concept of this system is hierarchically layering the tactile sensation, which is inspired by the flow of human perception. The tactile sensation is classified from low-order of tactile sensation (LTS) to high-order of tactile sensation (HTS), and also to preference. Here, LTS will be correlated with physical measures. Furthermore, the physical measures that are used to correlate with LTS are selected based on four main aspects of haptic information (roughness, compliance, coldness, and slipperiness), which are perceived through human tactile sensors. By using statistical analysis, the correlation between each hierarchy was obtained, and the preference was derived in terms of physical measures. A verification test was conducted by using unknown samples to determine the reliability of the system. The results showed that the system developed was capable of estimating preference with an accuracy of approximately 80%.

Cell detachment is an essential process in adherent cell culture. However, trypsinization, which is the most popular detachment technique used in culture, damages cellular membranes. Reducing cellular membrane damage during detachment should improve the quality of cell culture. In this article, we propose an enzyme-free cell detachment method based on resonance vibration with temperature modulation. We developed a culture device that can excite a resonance vibration and control temperature. We then evaluated the cell detachment ratio and the growth response, observed the morphology, and analyzed the cellular protein of the collected cellsmouse myoblast cell line (C2C12). With the temperature of 10 degrees C and the maximum vibration amplitude of 2m, 77.9% of cells in number were successfully detached compared with traditional trypsinization. The 72-h proliferation ratio of the reseeded cells was similar to that with trypsinization, whereas the proliferation ratio of proposed method was 12.6% greater than that of trypsinization after freezing and thawing. Moreover, the cells can be collected relatively intact and both intracellular and cell surface proteins in the proposed method were less damaged than in trypsinization. These results show that this method has definite advantages over trypsinization, which indicates that it could be applied to subcultures of cells that are more susceptible to trypsin damage for mass culture of sustainable clinical use. Biotechnol. Bioeng. 2017;114: 2279-2288. (c) 2017 Wiley Periodicals, Inc.

Droplet-based mu TAS, which carries out biochemical inspection and synthesis by handling samples as droplets on a single chip, has been attracting attentions in recent years. Although miniaturization of a chip is progressed, there are some problems in miniaturization of a whole system because of the necessity to connect syringe pumps to the chip. Thus, this study aims to realize a novel droplets generating device for droplet-based mu TAS using electro-conjugate fluid (ECF). The ECF is a dielectric liquid generating a powerful flow when subjected to high DC voltage. The ECF flow generation allows us to realize a tiny hydraulic power source. Using the ECF flow, we can develop a droplet generating device for droplet-based mu TAS by placing minute electrode pairs in flow channels. The device contains two channels filled with the ECF, which are dispersed and continuous phases meeting at a T-junction. When a sample in the dispersed phase is injected by the ECF flow to the continuous phase at T-junction, droplets are generated by shearing force between the two phases. We conducted droplet generating experiment and confirmed that droplets are successfully generated when the flow rate of the continuous phase is between 90 and 360 mm(3) s(-1), and the flow rate of the dispersed phase is between 10 and 40 mm(3) s(-1). We also confirmed that the droplet diameter and the droplet production rate are controllable by tuning the applied voltage to the electrode pairs.

Cell detachment and reseeding are typical operations in cell culturing, often using trypsin exposure and pipetting, even though this process is known to damage the cells. Reducing the number of detachment and reseeding steps might consequently improve the overall quality of the culture, but to date this has not been an option. This study proposes the use of resonant vibration in the cell cultivation substrate to selectively release adherent calf chondrocyte cells: Some were released from the substrate and collected while others were left upon the substrate to grow to confluence as a subculture-without requiring reseeding. An out-of-plane vibration mode with a single nodal circle was used in the custom culture substrate. At a maximum vibration amplitude of 0.6 mu m, 84.9% of the cells adhering to the substrate were released after 3 min exposure, leaving a sufficient number of cells for passage and long-term cell culture, with the greatest cell concentration along the nodal circle where the vibration was relatively quiescent. The 72 h proliferation of the unreleased cells was 20% greater in number than cells handled using the traditional method of trypsin-EDTA (0.050%) release, pipette collection, and reseeding. Due to the vibration, it was possible to reduce the trypsin-EDTA used for selective release to only 0.025%, and in doing so the cell number after 72 h of proliferation was 42% greater in number than the traditional technique.

Cell patterning methods have been previously reported for cell culture. However, these methods use inclusions or devices that are not used in general cell culture and that might affect cell functionality. Here, we report a cell patterning method that can be conducted on a general cell culture dish without any inclusions by employing a resonance vibration of a disk-shaped ultrasonic transducer located under the dish. A resonance vibration with a single nodal circle patterned C2C12 myoblasts into a circular shape on the dish with 10-min exposure of the vibration with maximum peak-peak amplitude of 10 μm${}-{\text{p-p}}$. Furthermore, the relationship between the amplitude distribution of the transducer and the cell density in the patterned sample could be expressed as a linear function, and there was a clear threshold of amplitude for cell adhesion. To evaluate the cell function of the patterned cells, we conducted proliferation and protein assays at 120-h culture after patterning. Our results showed that the cell proliferation rate did not decrease and the expression of cellular proteins was unchanged. Thus, we conclude, this method can successfully pattern cells

In the textile industry, fabric hand is one of the crucial aspects that influence the value of fabric. However, the judgement of fabric hand may vary across subjects. Thus, this study proposes to group the subjects based on their evaluation of fabric hand, and the tactile sensations that are dominantly related to fabric hand are investigated. First, a sensory evaluation of eight knitted fabric samples was carried out using 14 verbal expressions of tactile sensation. These 14 verbal expressions were hierarchically classified into three stages which were called as low-order of tactile sensation, high-order of tactile sensation and lastly, fabric hand. After grouping the subjects by using cluster analysis, a principal component analysis was conducted in each stage of tactile sensation to gather the strong correlations of the verbal expressions. Then, the correlations between principal components of each stage were determined by multiple regression analysis. As a result, the study showed that the subjects could be mainly grouped into two. The former group expressed fabric hand as good when the fabric is soft and moist. On the other hand, the latter group defined good fabric hand when the fabric is silky and smooth.

Making cell culture process automated and efficient is one of the biggest challenges for cell therapy including regenerative medicine, drug screening and body-on-chip drug development. Cell culture process with cell seeding, culturing, detaching and collecting processes is in general conducted manually by a technician. To establish an efficient and stable mass culture process of cells, "informotion technology" may play an important role. By automating cell culture process with actuator/sensor technology and networking them online, know-hows to deal with living cells can be shared. By doing so, we may efficiently provide large number of cells, ready for accelerating regenerative medicine spread. Ultrasonic actuation technology has proved its potentials to be used for cell culture automation.

When co-culturing cells outside the body, it is necessary to culture in an environment closer to the living body. In this study, we tried to manufacture a culture vessel and generate three-dimensional tissue of cells by acoustic radiation pressure and Ekman transport. As a result of experiments with particles simulating cells, the particles remained outside the culture surface in the case of only using acoustic radiation pressure. However, by combining Ekman transport and acoustic radiation pressure, particles could be aggregated efficiently. Therefore, three-dimensional tissue of cells can be generated using these techniques.

シートベルトウェビング（ベルト部分）は乗車に際して必ず触れるものであり，製品開発において触感の向上が重要な課題のひとつである．シートベルトウェビングの触感向上に関する先行研究の多くは触感を説明する要因として物性値を測定しているが，ヒトが触覚受容器の応答によって触感を知覚することに鑑みると，物性値のみでは必ずしもシートベルトウェビングの触感を言い表せるとは言えない．このため，本研究では物性値だけでなくシートベルトウェビングを触察した際の振動情報も用いて触感を定量化した．被験者に7種類のサンプルをSD法により評価させ，その結果から主成分分析を用いてシートベルトウェビングの触感に関する主成分を求めた．この結果，低次触感では「粗滑感」「硬軟感」「湿感」，高次触感では「高級感」の主成分が抽出された．つぎに，サンプルの物性値および触察時の振動情報を測定し，重回帰分析を用いて，物性値および振動情報と触感に関する主成分の関係を定式化した．この結果，物性値および振動情報から触感を予測する線形モデルを構築した．

近年，細胞の医療応用に注目が集まっている．これに伴って効率的な細胞培養法が研究されており，とくに細胞剥離に関する研究が盛んである．一般的にはトリプシンに浸漬した細胞に対してピペッティング等の機械刺激を付与することで細胞を剥離する．トリプシンの毒性を鑑みると，低濃度のトリプシンを用いることが望ましいが，細胞の剥離率が低下してしまう．そこで，本研究では，超音波の併用よって低濃度のトリプシンによる細胞剥離を実現した．汎用フラスコに接着した接着細胞の下方から超音波を付与する装置（図）を開発した．さらに，バースト波を用いた超音波照射によって温度上昇を抑制しつつ，高強度の超音波を細胞に付与した．この結果，ピペッティングでは一部の細胞のみが剥離する低濃度トリプシンを用いた際にも，超音波の照射によって全細胞が剥離した．低濃度トリプシンで細胞剥離を実現したことで細胞の増殖性が向上したこと，超音波照射によるタンパク質発現の変化や代謝に異常がないことを確認した．

近年，柔軟軽量なソフトロボットに関する研究が広く行われており，ロボットハンドもその対象として注目されている．ロボットハンドが様々な形状の物体を把持するには多様な把持姿勢の実現が求められる．すなわち，ロボットハンドを構成するロボットフィンガには，屈曲伸展運動に加えて内転外転運動が必要になる．このため，本研究では，屈曲伸展運動および内転外転運動が可能なソフトロボットフィンガを具現化する．開発したソフトロボットフィンガはアラミド繊維で繊維強化されたシリコーンゴム製のチューブで構成される．チューブ内部には半円筒状の閉流路が2本設けられており，それぞれ独立して内部を加圧できる．閉流路を加圧するとチューブは膨張するが，周方向および手掌側に配置された繊維によって，その膨張は一部拘束される．結果，双方の閉流路を加圧するとフィンガは屈曲し，一方の閉流路を加圧するとフィンガは内転する．本フィンガは，直径7.0 mm，全長60 mm，質量0.70 gであり，上記閉流路を最大14 kPaで加圧した際の最大屈曲角度および内転角度はそれぞれ79°および34°であった．

Growth control is an important technique in plant markets, for appropriate shipping time of plants (e.g., flowers and fruits) allows for reducing production costs for post harvesting storage and pesticide. It is favorable to control plant growth without any chemicals physical stresses are attractive candidates for this purpose. Here, we propose an ultrasound-based technique to control plant growth.