Micro System Integration Center, Tohoku University

At the Hands-on-access Fabrication Facility, more than 150 equipment related to prototype development of various devices centering on MEMS are open to companies and universities to support their research and development activities and practical application.  Users can use the equipment they need when they need it (charges are based on the equipment used and time).  And companies and laboratories that do not have appropriate prototype development facilities dispatch engineers and students to create prototypes themselves.  It reduces risks and costs.  You can use the know-how accumulated at Tohoku University, and full-time staff will provide maximum support for device design, process design, equipment operation, etc.  One of characteristic technologies is "silicon migration seal(SMS) packaging technology", that does not use a film-forming process for vacuum sealing.  It is also possible to train engineers with actual development experience during prototype development.  In the Hands-on-access Fabrication Facility, companies can also manufacture products under certain conditions.  Since its start in 2010, it has been used by over 300 companies, and over 60 universities / public research institutes.  

The system prototype consists of a capsule-type thermometer device and a receiver installed outside the body. Once inside the stomach and in contact with gastric juices, the device generates electricity and charges an internal capacitor.  Since it does not contain a primary battery, it can be used safely inside the body.  The electrical energy is used to drive a thermometer in the intestines to continuously measure the core body temperature.  Measurement data is transmitted wirelessly to a receiver placed in the clothes outside of the body. This allows to measure the resting basal body temperature, which is one of the most important indicators of health, as well as the core body temperature and its changes (circadian rhythm).

The temperature-fluctuation power generation system (TF-PGS) has a structure that combines a micro thermoelectric element and a heat storage material (Phase change material: PCM). The thermal storage material absorbs or dissipates heat from its surroundings to maintain the temperature near the phase change temperature. The heat storage material is a mixture of existing phase change materials and nanomaterials to control the desired operating temperature, heat storage volume, and heat uptake rate. The generated electrical energy is stored in a micro-storage device and used only when necessary. In principle, this element for TF-PGS does not require a heat source, enabling the sensor to be powerless and realizing an independent sensing system. Since the amount of electricity generated when the temperature change is applied is proportional to the volume of the heat storage material, a palm-top sized TF-PGS with various volumes has been developed. The output voltage of thermoelectric devices is very small, ~ mV range, thus, the voltage must be amplified in order to store it efficiently in a micro-storage device. For this reason, we developed a DC-DC converter that amplifies the low-voltage thermoelectric output with high efficiency. We also developed a power management circuit that controls the storage of energy in energy storage devices and the supply of energy from the storage devices to sensors. In addition, a supercapacitor with large capacity was developed as a micro storage device.

In catheter treatment for vascular lesions such as atherosclerosis, imaging of the lesion will enable treatment secure . Ultrasound measurement is more appropriate than optical measurement because diffuse reflection of light by the blood cells will occur in the intravascular. We develop a forward-looking ultrasound imager able to 3-dimensional imaging of intravascular (Fig.1). We aim for diameter reduction (outer diameter 2.5mm), higher frequency (20MHz), and multi-element (24 elements) of the probe. We use a piezoelectric single crystal(PMN-PT). The device has a structure equipped with a backing material to the short pulse and to reduce vibration in the rear direction(Fig.2). We are using sandblasting, which can be processed into an arbitrary shape PMN-PT (Fig.3).

Blood pressure is one of the most important information indicating the condition of the human body among biological information, and abnormalities of heart and vascular system will be reflected sensitively. We have developed an ultra-miniature fiber-optic pressure sensor of 125 µm　in diameter by micromachining technology and optical technology. We aim to measure the local blood pressure in intravascular stenosis, microvasculature, children and small animals in catheter treatment (Fig 1). The sensing element, which is composed of a thin diaphragm, is fabricated by micromachining technology on the fiber end, and the diaphragm deformation caused by pressure can be detected by using white light interferometry(Fig2,3). This sensor has various advantages, for example, it can be used in such electromagnetically harsh environments, and it can be produced at a relatively low cost because a lot of sensor chips can be batch fabricated by semiconductor microfabrication technology. The blood pressure of a goat was able to measure by using this sensor (Fig.4).