RF-microwave sensor development for cell and human in vitro and ex vivo monitoring

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa auditorium L2, remote link: https://oulu.zoom.us/j/62440424576?pwd=ZXRyaWNXbm5ZM1pRWG5teVRRK2FGZz09

Topic of the dissertation

RF-microwave sensor development for cell and human in vitro and ex vivo monitoring

Doctoral candidate

Master of Science (Technology) Joni Kilpijärvi

Faculty and unit

University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Microelectronics Research Unit

Subject of study

Electrical Engineering


Professor Karol Malecha, Faculty of Microsystem Electronics and Photonics, Departament of Microsystems, Wroclaw University of Science and Technology, Puola


Docent Jari Juuti, Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu

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Novel biosensors for cell and human measurement

New types of biosensors for measuring cells and humans In the dissertation, sensors suitable for measuring human beings were developed for several different use cases. The sensors were based on RF sensor integrated on chip and various microwave-based resonators. Cases included cell culture, water salinity at human body salinity levels, and artificial skin measurement by simulating changes in fluid balance.

Modern activity meters, sports watches, or rings measure a number of different things about human activity, such as heart rate, movement, distance, and sleep. The measurements of these functions are basically based on sensors e.g. for measuring the optical response and acceleration of the body and for measuring position via a GPS antenna. On the basis of activity measurements, there is always information produced by the sensors and further conclusions are made, such as performance on a running run or sleep quality measurement with advanced algorithms from heart rate and acceleration sensor data. The same principles can also be used to measure a basic part of life, a cell. Through a signal describing the state of a cell in cell culture, its life can be monitored continuously throughout its life cycle. In this case, for example, the effects of new drugs or harmful substances on the cell in different types of situations can be studied.

The dissertation research used a custom silicon-based chip, as a biosensor, where sensors integrated into the chip could convert the phases of cell life into an electrical signal and monitor it in real time. However, the challenge was to combine “wet” biological materials with “dry” electronics due to the living conditions of the cells. The solution to the problem was found in the ceramic-based packaging technology developed in this work, which allowed the chip to be used reliably for cell culture measurement for long periods of time. In the future, such measurement systems may replace traditional optical inspection methods using, among other things, cell dyes. In addition, a system was developed which can be used to study, for example, the composition of body fluids. The system was based on a combination of a microwave sensor and microfluidics, which allows use of very small amounts of liquid in the necessary way and the measurement and changes of the electrical (dielectric) values of the sample. In the work, a system was developed that could determine and monitor the salinity of one microliter of fluid (a drop of blood is about 50 µl), which varied to the same extent as in the human body. The dissertation also focused on real-time and non-invasive measurement of fluid balance. In the work, a small-sized ring oscillator-based microwave sensor was developed for this purpose. Its function was tested using laboratory-made artificial skins that corresponded to the right skin properties in different body fluid balance situations. In future smartwatches, liquid balance measurement could be a useful for completely new feature alongside previous functionalities if proposed sensor system can be miniaturized to a sufficient level.
Last updated: 6.10.2021