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Thermal Engineering, Bioengineering, and Biothermal Engineering
- Interdisciplinary Research on Heat and Mass Transfer and Devices -

The Heat and Mass Transfer Laboratory is dedicated, but not restricted to, studies of heat and mass transfer in biological systems. Our research covers a broad area associated with thermal engineering, bioengineering, and biothermal engineering.

(1) Measurements of thermal conductivity in infinitesimal samples within a millisecond, and of thermal transport properties of a solid at a touch or without contact.

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Scanning electron micrograph
of a micro-beam MEMS sensor.

Thermal transport properties are important to the design of many kinds of equipment and processes. One of our research projects is working to develop new techniques to measure thermal conductivity and the thermal diffusivity of gases, liquids and solids, including biological materials. As opposed to the variety of methods and techniques that have been developed for the precise measurement of thermophysical properties, we are developing new methods that are applicable to in-situ measurement of biological samples. Current projects include (a) a micro-beam MEMS sensor for measurements of one drop of a liquid sample or small gas samples, (b) a noncontact measurement method for solids or biological materials using laser heating, (c) a stamp-type contact sensor for non-invasive measurement of solids, and (d) a needle-type sensor for measurement of biological and soft materials.

(2) Freezing technology; to kill or preserve cells.

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A cryomicroscope,
used to study freezing injuries of cells.

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An ice ball formed around
a cryoprobe.

When living cells or tissues are frozen, their viability depends on their cooling rate, the cooling temperature and the parameters associated with the cryoprotective agents. Cells are either necrotized or successfully preserved, depending on the biophysical events that occur during freezing and thawing. To obtain a successful result during cryosurgery or cryopreservation, which are used for opposite objectives, both scientific and engineering studies are still needed. To this end, cryobiological studies are used to understand the mechanism of freezing damage in cells and tissues, and biothermal engineering helps us to understand temperature history and predict cell response during a freezing process. We are conducting cryobiological studies with the use of a cryomicroscope and a perfusion microscope, which was developed in house. We are also conducting experiments to study freezing around a cryoprobe, as well as analytical work to create models of the freezing processes.

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Simulated distribution of electric
potential during electroporation.

(3) Non-thermal medication applied by irreversible electroporation
Electroporation is a technique used to perforate the cell membrane by applying a pulsed voltage to the cells. When the cells are exposed to a high-voltage pulse beyond a certain threshold, they necrotize due to irreversible damage, which is called irreversible electroporation (IRE). One of the advantages of IRE for use in medical treatment is that the extracellular matrix (ECM) may be kept intact, which is favorable for healing (i.e. regeneration of tissue). For a successful IRE, however, thermal damage to the ECM resulting from Joule heating within the tissue must be avoided. Targeting the clinical application of IRE, we are engaged in both experiments and theoretical analysis to estimate the distribution of electric fields, temperature rise, ECM damage, and cell necrosis during IRE.

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Architecture of bone
measured by micro-CT.

(4) Mass transfer in bone and its application to bone regeneration
Bone is a hard material composed of collagen and apatite. Although it looks like a static structure, it is constantly being remodeled by dynamic cellular activity with the aid of body fluids containing various stimulating substances that are circulating in a three-dimensional lacunocanalicular network in the bone. When the bone receives an external load, as it does during walking and exercise, the activities of the bone cells change because of the deformation of cells and the enhancement of fluid transport inside the bone. We are conducting studies of the relationships that exist between mechanical stimulation, mass transfer inside the bone, functional changes of the bone cells, and the consequent bone remodeling. The findings would be useful in the development of a method of efficient bone tissue regeneration.

Heat and Mass Transfer Laboratory,
Department of Mechanical Engineering, Faculty of Engineering, Kyushu University
Professor Hiroshi Takamatsu
Associate Professor Kosaku Kurata
Assistant Professor Hai Dong Wang
Research Technician Takanobu Fukunaga
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