Development of an impedance-based flow rate sensor


Silver nanoparticles (AgNPs) exhibit favourable characteristics such as antibacterial and antiinflammatory activity, rendering them of great interest for many biomedical applications. Their outstanding usage raising concerns about the AgNPs’ interaction with biological material both at the nano- and macroscale. To understand large-scale impacts of AgNPs on the environment and to reveal the level at which AgNPs are present, there is a necessity for a sensor device to detect and characterize AgNPs in solution. Here, we use an electrochemical detection method based on the oxidation of AgNPs at an appropriately biased electrode to estimate the underlying AgNP concentration in solution [1, 2]. Towards a reliable flow-over sensor system, we want to use a microfluidic environment to enhance the detection frequency that is currently governed by passive diffusion [3]. In order to optimize the flow characteristics, there is a need to monitor flow rates in the sub-µl/min regime. In this project, we aim for an impedance-based electrochemical transducing mechanism providing reliable flow rate measurement in a challenging environment [4, 5].

Aim & research methods

In order to calibrate the electrochemical flow rate sensor, you will develop a simple sensor system with additive manufacturing techniques. To this end, you will…

  1. …fabricate your own microfluidic systems via stereolithography (3D printing) and ink-jet printing,…
  2. …establish an experimental setup to easily monitor flow rates based on electrochemical impedance spectroscopy…
  3. …investigate favourable operating regimes for reliable measurements in the sub-µl/min regime and finally deduce a calibration curve for your custom-built sensor.

You will be introduced in an interdisciplinary working environment and will learn the following techniques:

  1. additive manufacturing approaches (stereolithographic 3D printing, inkjet printing, drop casting)
  2. optical evaluation techniques, such as microscopy and profilometry
  3. microfluidic circuitry based on laminar flows
  4. electrochemical impedance spectroscopy (EIS) and other electrochemical methods


  1. background in chemistry, physics or engineering science
  2. wet-lab experience and excellent analytical and experimental skills
  3. dedication and motivation to work on an interdisciplinary research topic self-reliantly

Possible starting date & further information

Potential starting date is as soon as possible. For further details and application contact Lennart Weiß in person or via email.


  1. S. V. Sokolov, S. Eloul, E. Kätelhön, C. Batchelor-McAuley and R. G. Compton, "Electrode–particle impacts: a users guide," Physical Chemistry Chemical Physics, vol. 19, no. 1, pp. 28-43, 2017.
  2. K. Krause, A. Yakushenko and B. Wolfrum, "Stochastic On-Chip Detection of Subpicomolar," Analytical Chemistry, vol. 87, pp. 7321-7325, 2015.
  3. T. Alligrant, M. Anderson, R. Dasari, K. Stevenson and R. Crooks, “Single nanoparticle collisions at microfluidic microband electrodes: the effect of electrode material and mass transfer,” Langmuir, vol. 30, pp. 13462-13469, 2014.
  4. K. Y. Tam et al., “A channel flow cell with downstream impedance spectroscopy detection: theory and application.”, Electroanalytical Chemistry, vol. 407, pp. 23-35, 1996.
  5. J. Collins and A. P. Lee, “Microfluidic flow transducer based on the measurement of electrical admittance.”, Lab Chip, 4, 7-10, 2004