Development of an optofluidic absorption platform for detection of inorganic ions in water

The purpose of Gerwin’s work was the development of an optofluidic absorption platform for detection of inorganic ions in water. First, the methodology was established. The absorption differences of 16 different electrolytes in regard to water were determined with a spectrophotometer (device to determine the absorption per wavelength). These were found to be unique for the different electrolytes and the signal is linear dependent on the concentration (if the number of ions in a fixed amount of water is doubled, then also the signal is doubled). This makes the method suitable for the sensor.

Second, the absorption difference of an electrolyte compared to that of demineralized water was studied when another salt was dissolved. It was concluded that at higher temperatures the presence of the first dissolved salt has less influence on the signal originating from the second dissolved salt.

Integrated optofluidic sensors are designed after the methodology was established. The requirements of the sensor were taken into account. Unfortunately, the fabricated sensors deviated from the expected results. Therefore the chips were studied with different microscopes. This study led to improvements in the design which were also realized by LioniX. The first results were obtained with these chips and although a deeper analysis is required, it can be said that the first foundation has been laid to identify and quantify ions in water with integrated optofluidic sensors based on absorption spectroscopy.