Copyright 2011 Laboratory of Micro and Nanomechanics, Hokkaido University, Japan

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Laboratory poster




Biomechanics

Our specific research interests are: measurement of cell traction forces, chondrocyte biomechenics, tenocyte mechanobiology, mechano-regulation of myofibroblast alignment, and development of single-cell bioassay system.

Development of Newly Designed Bioassay System for High-Throughput Single Cell Analysis
Over the last decade, microfluidics or “lab-on-a chip” technologies have been of great interests of a number of researchers as these technologies can be used as a biological assay system (e.g. cancer screening). Through an active collaboration with Dr Helen Andersson-Svahn at Royal Institute of Technology (Kungliga Tekniska hogskolan, KTH), we are developing a bioassay system consisting of an active microfluidic device integrated on the microwell plate for a high-throughput single cell analysis. This novel device can also be used for study of cell biomechanics under fluid shear stress.





Study on Measurement of Traction Forces Generated by Smooth Muscle Cells

It has been shown that intracellular structures rearrange according to changes in mechanical environments to which cells are subjected. In particular, cellular traction forces are believed to play an important role in the interactions between cells and their substrates, possibly involving the process of the cell remodeling. Although many studies have been performed to estimate cellular traction forces using microfabrication techniques, little is known of the effect of mechanical environments on the magnitude and direction of traction forces and hence how intracellular structures contribute to traction forces. This study addresses fundamental aspects of how these cytoskeletal structures contribute to smooth muscle cell mechanics.

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Mechanobiology of Chondrocyte Study of Chondrocyte in Response to Mechanical Stress

It is essential for cartilage health and application in cartilage tissue engineering to know chondrocyte mechanotransduction-the process by which cells sense and respond to mechanical signals. We study mechanical properties of chondrocytes by using a micropipette aspiration technique in which the surface of the cell is aspirated into a small glass tube. This technique can measure the Youngfs modulus of cells and can be utilized to apply mechanical stress to cells. Chondrocytes can be isolated from bovine metacarpal-phalangeal joints by a process of sequential enzyme digestion. To investigate how they respond to mechanical stress, we measure the Youngfs modulus of cells by applying suction pressure which is controlled by a syringe pump. The Youngfs modulus was determined by a previous study.This project is collaborated with Dr. Martin Knight and Professor Dan Bader at Queen Mary, University of London (UK).

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Mechanical responses of Myofibroblast to cyclic Stretching

A wound healing is divided to three phases that are inflammatory phase, growth phase and mature phase. Myofibroblasts grow proliferously in the growth phase and align a certain direction. If they align a certain direction, a wound cures at early date, in contrast if they doesn’t align, a wound healing delays. But, it is unrevealed that what causes this alignment. we hypothesize that tensile stimulations of skins occurred by movements of dairy actions, and to reveal this hypothesis, we run a stretching experiment of myofibroblasts on the condition that a stretching rate is 1Hz and a stretching magnitude is 20%. After stretching, we observe an alignment of them with microscopy. At the same time, to observe their cytoskeleton, we run a fluorescence staining of actin filaments and an immunofluorescence staining of vinculins.

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Mechanobiological Responses of Tenocytes to Interstitial Fluid Flow with/without the Presence of Cyclic Tensile Strain

Tendon is collagenous, soft connective tissue in articular joint, predominantly subjected to tensile loading. Tendon possesses water for approximately 60% of its wet weight. This water imposes fluid shear stress to tendon cells, tenocytes, when tendon matrix is stretched. Thus, local mechanical environment of tenocyte includes both tensile strain and fluid shear stress. In conjunction with MEMS techniques, this project develops a microfluidic device which enable to apply controlled tensile strain and fluid shear stress to isolated tenocytes in vitro, and examine their synergetic effects on tenocyte mechanotransduction events and associated mechano-regulation of tenocyte metabolism. This research project is in collaboration with Prof. James Wang at University of Pittsburgh.



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Heat transfer engineering

Primary reseach topics are heat transfer with phase change, heat and mass transfer in non-linear system.

Heat transfer and Thermophysical Properties of non-Newtonian Fluid

A non-Newtonian fluid is defined as the fluid that has non-linear relationship between the shear rate and the shear stress (see Fig. A). A lot of fluids around us can be categorized into the non-Newtonian fluids. For example, paints, inks, foods, slurry, and some kind of cosmetics show the properties of non-Newtonian fluid. 
As the thermophysical properties as well as the transport properties of these fluids are affected by the shear conditions, it is necessary to know the mechanism of heat and mass transfer of the non-Newtonian fluid in a variety of path and on a variety of heated surface from the view point of practical use of the fluids.
In the present research theme, we measure the above mentioned heat transfer characteristics as well as the thermophysical properties under a variety of shear conditions of the non-Newtonian fluids. 
A DSC (Differential Scanning Calorimeter: Fig. B) and the other measurement equipments are employed to measure the thermophysical properties such the specific heat of the samples. For the measurement of the thermal conductivity, the modified probe is employed. A cylindrical probe (heater) of the measurement facility is set vertically in the sample fluid.

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Fig. A@Relationship between@@@@@@@@@@@Fig. B@Differential Scanning Calorimeter
shear rates and shear stress



Mechanism of Melting Heat Transfer of Ice Slurry Flow and its Applications

Ice slurry has drawn a large attention as a cold thermal storage medium for its fluidity and high thermal storage density. In addition, there is a potential to apply the ice slurry to the quenching or quick cooling of the material with large heat capacity. In the preset research theme, melting heat transfer characteristics of the ice-slurry under a variety of conditions are investigated both theoretically and experimentally. 
The objective of the present study is to propose the effective method to promote the melting heat transfer of ice particles in the ice slurry flow. As the promotion method of the melting of ice particles in the ice-slurry, we have proposed to employ the impinging jet of ice-slurry (see figure below) and the swirl flow of ice-slurry. 
The melting heat transfer characteristics of the ice slurry are investigated experimentally. In order to measure the local ice-particle density in the ice slurry flow, the measurement system using a single fibber-optic cable and a He-Ne laser has been developed. The distribution of the ice particles near the heated surface are investigated under a variety of flow conditions.
In the theoretical approach, a numerical simulation on the movement and melting of ice-particles are carried out by using MPS method to determine the effect of flow conditions on the promotion of the melting of the ice-slurry.

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Ice slurry(Ethylene glycol aqueous@@@@@@@@Impinging jet method to promote the 
solution and ice particles)@@@@@@@@@@@@@ contact melting of ice particles