Research seeds

“Realization of multi-functional and integrated (multi-modal) sensor using LSI process”

 Semiconductor products such as transistors and ICs do not like water, so if they are immersed in water, overcurrents will flow in unexpected places and break immediately.However, by successfully combining the semiconductor LSI process and improving the waterproof performance, we have succeeded in developing an element that can operate stably without breaking even when immersed in water.Based on this technology, we are conducting research on semiconductor-type sensor chips that can accurately capture chemical and physical natural phenomena and convert them into electrical signals and numerical data.
Until now, we have been conducting research on various semiconductor-type sensor elements, such as pH sensors, temperature sensors, electrical conductivity sensors, redox potential sensors, and moisture content sensors, for aqueous solutions and soil.
We are exploring the principles and phenomena of sensors in depth, researching how to realize them with the Si-LSI process, and how to perform high-performance and long-term measurement.
A small sensor chip in millimeters can be made by the LSI process, realizing on-site measurement (on-site monitoring) in places where measurements could not be made before (living body, soil, groundwater, inside piping, etc.)

“Development of new measurement method for severe environmental monitoring”

Existing monitoring methods cannot provide sufficient performance to monitor harsh environments such as soil, living organisms, and high-pressure groundwater.For this reason, we are developing new methods suitable for each measurement environment and aiming to realize long-term and stable sensors.
For a new sensor that predicts the amount of soil moisture and the concentration of ions contained in the moisture of a sensor aimed at predicting landslide disasters, we are studying a method of extracting soil physical properties by electrical impedance measurement.
A multimodal sensor that drives many types of sensors at the same time was realized by using frequency separation technology and calculating the optimal operating point.
n addition, we propose and demonstrate various measurement methods, and have applied for many patents and submitted academic papers.

“Development of drive circuit for continuous driving of various types of sensors”

 When driving a semiconductor sensor chip with a new measurement method, the driving circuit is indispensable for verifying its operation.Especially in on-site measurement such as precision agriculture and landslide prediction, not in the laboratory, it is difficult to install large equipment and long-term measurement is also difficult.
In this laboratory, after verifying the optimal operating point and driving method, we are implementing a driving circuit design for on-site measurement.This is an important step in turning ideas derived from basic experiments and mathematical formulas into reality.By taking your own designed sensors and drive circuits to the field and measuring them, you will be able to know various problems that were not found in the laboratory and will be able to deepen your understanding.
By repeating design, measurement, and improvement, we try to create a sensor system that is truly needed.

Application examples

“Multipoint measurement in soil and medium in precision agriculture”

It is expected that higher yields, higher functionality and higher added value of agricultural products will be further advanced.Monitoring the cultivation environment plays an important role.In particular, more and more development direct of monitoring in soil and medium is desired.
Our laboratory is conducting research on multi-modal sensors that can measure soil temperature, nutrient concentration and pH for monitoring in soil and medium.We have succeeded in forming a temperature sensor, electrical conductivity sensor, and pH sensor on a Si semiconductor substrate by an LSI process, and have realized on-site monitoring while inserted in the culture medium.

“Measurement of water content in soil for prediction of landslide disaster”

Landslides (slope failures) due to heavy rains, etc., endanger the lives of not only houses but also humans and cause great damage.In general, sensors are used to detect the beginning of collapse, which is useful for evacuation immediately before collapse.
In our laboratory, we are developing sensors for predicting landslide disasters that allow us to go one step further and know the level of danger before collapse occurs.The amount of water contained in the soil increases due to rain, etc., the frictional force of the soil decreases, and the weight of the soil containing water increases, causing slope failure.With this mechanism, we are working on a sensor that can continuously measure the moisture content in the soil that can be used on mountain slopes, and that we are trying to connect it to prediction.
We have developed a semiconductor-type impedance measurement sensor and clarified the relationship between soil moisture content and sensor output.And we are still observing the long-term moisture change for more than 3 years.

“Swallowable capsule sensor for chemical analysis”

It is important to observe the inside of the body precisely regardless of the human body or organism.If the chemical analysis function can be added to the capsule endoscope, the analysis accuracy will be dramatically improved.We have been developing capsule-type chemical analysis sensors by miniaturizing the system by using a small-sized semiconductor sensor chip (multi-modal sensor) that integrates multiple types of sensors, realizing battery operation and wireless transmission of data.Using this, we succeeded in real-time measurement and wireless transmission of electrical conductivity and temperature from the rumen of dairy cows in the livestock industry.In the future, we will aim for further integration of sensors such as pH and redox.

Research tools

Based on sensor technology and electronic circuit technology, we are conducting research using the following various devices.

Electric field simulator ElecNet, DC power supply / oscillator manufactured by Keysight (formerly Agilent Technologies),
Tektronix oscillator, Graphtec data logger, vacuum oven,
Stereo microscope, ultrapure water generator, 3D printer, etc.