Student Project: Miniaturized embedded electrochemical sensor for environmental application

What you will do

Conductivity is one of the most often determined fluid parameters and is a measure for the total amount of dissolved ions. To determine conductivity, the resistance of a fluid sample located in the area between at least two electrodes is determined by impedance spectroscopy. The conductivity is then given by multiplying the measured conductance with the so-called cell constant of the sensor (Kcell).

The conductivity range that can be determined with a sensor depends on the chosen Kcell. This implies that a correct conductivity sensor must be chosen, fitting with the expected concentration range in the targeted application.

Commercially available conductivity sensors utilize two parallel planar electrodes (with a certain area and distance that define the Kcell). Such a geometry is difficult to miniaturize. However, Timmer et al [1] describe how planar interdigitated 2-electrode sensors on chip can be designed and how the Kcell value can be derived. A disadvantage of the 2-electrode conductivity sensor is the large electrode-electrolyte interface resistance which limits its application for a wide range of conductivity solutions. To minimize this, a 4-electrode sensor can be used, in which one pair of electrodes are injecting the current, while the other pair are sensing the voltage. We have extended this concept to microfabricated 4-electrodes conductivity sensor [2].

For sensor to be embedded in concrete, so far 4 electrode measuring principle has not been tested. The use of four-electrode technique will open new possibilities for concrete application. Moreover, the same investigation in agricultural substrate, like rock wool, will give new insight of the sensor performance.

[1] B. Timmer, W. Sparreboom, W. Olthuis, P. Bergveld and A. van den Berg, “Optimization of an electrolyte conductivity detector for measuring low ion concentrations,” Lab Chip, vol. 2, pp 121-124, 2002

[2] Brom-Verheijden, Greja JAM, Martijn H. Goedbloed, and Marcel AG Zevenbergen. "A Microfabricated 4-Electrode Conductivity Sensor with Enhanced Range." Multidisciplinary Digital Publishing Institute Proceedings. Vol. 2. No. 13. 2018.

Tasks:

• Literature search (4-electrode impedance measurement, moisture detection sensors).
• Experimental work to investigate optimized parameters for measurements in concrete and agricultural substrates.
• Give advice and/or design a new 4-electrode conductivity sensor with a specified Kcell that fits the target applications.

Who you are

• You are a Msc or Bsc student in Applied Physics, Biomedical Engineering, Chemical Engineering, Electrical Engineering, Mechanical Engineering or Mathematics.
• You are available for a period of 6 months.
• Affinity for experimental work in the lab.
• Interest and knowledge of sensor specifications, especially electrochemical sensors.
• Motivated student eager to work independently and expand knowledge in the field.
• Good written and verbal English skills.
• Entitled to do an internship in the Netherlands. 

Interested

Click on ‘apply’ to submit your application. You will then be redirected to e-recruiting.

Please be advised that non-EU/EEA country students that are studying outside of the Netherlands, need to have a work-permit to be able to do an internship in the Netherlands.