Stochastische Detektion von Nanopartikeln mit elektrochemischen Sensorfeldern
Messsysteme
Zusammenfassung der Projektergebnisse
Single-impact electrochemistry is an interesting detection concept for diluted species in solution. As it relies on the species’ stochastic collision with a microelectrode, it comes with features that are fundamentally different to amplitude-based sensing techniques. The high signal-to-noise ratio, the (theoretically) low limit of detection and the high sensitivity that can be achieved with this technique makes it an appealing approach for bio- and environmental sensing applications. However, in order to be exploited in such settings, optimized detection platforms that ensure a reliable quantification have to be implemented. In this project, we established a fabrication protocol for low-cost microelectrode array chips using screen printing technology and laser ablation. We demonstrated its capability by exemplarily detecting silver nanoparticle impacts at concentrations from 1 to 100pM. Furthermore, we studied preferential detection regimes and the influence of the electrolyte composition and concentration on the detection yield in such nanoimpact experiments. Most often, such measurements are operated under static conditions, where only diffusive transport is governing the sensor response. To improve the collision rate, we investigated strategies to counteract the particle adsorption and to enhance the mass transport towards the electrode surface. Our experimental studies were complemented by numerical simulations and theoretical considerations. Besides classical surface coatings that prevent unspecific adsorption, we exploited electrostatic repulsion by implementing another tunable electrode surface that surrounds all detection electrodes. With this approach, we were able to reduce the particle adsorption substantially compared to normal chips. In addition, we also explored electrokinetic transport effects that can be induced by such a macroscopic electrode. Here, on-chip micropumping was shown to further improve the collision rate at the detection electrodes. Besides electrokinetic phenomena, we built classical microfluidic channels with our own resin formulation that allowed a direct attachment between chip and structure. We designed a chamber that utilizes gravity-driven advection and studied the influence of different channel designs and coatings on the collision rate. Nevertheless, traditional flow-over sensors face the common issue of weak efficiency, as there are always particles in parts of the channel that cannot be detected before they are swept across the detection surface. To overcome this well-known issue, we induced chaotic mixing via herringbone structures and found a substantial increase in the detection yield. Complementary, we also tested if silver nanoparticles can be detected in paperbased microfluidics. We built a prototype and were able to resolve individual particles within a wax-patterned chromatography paper. This finding is in particular interesting, as it broadens the applicability of single-impact electrochemistry. In summary, our research indicates that single-impact electrochemistry might be successfully transferred from advanced laboratory setups into specific ultrasensitive detection devices.
Projektbezogene Publikationen (Auswahl)
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(2019). Electronic design automation for increased robustness in inkjet-printed electronics. Flexible and Printed Electronics, 4(4), 045002
Rinklin, P. et al.
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(2020). Biocompatible, flexible, and oxygen-permeable silicone-hydrogel material for stereolithographic printing of microfluidic lab-on-a-chip and cell-culture devices. ACS Applied Polymer Materials, 3(1), 243-258
Zips, S. et. al.
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(2020). Opportunities and challenges of translating direct single impact electrochemistry to high-throughput sensing applications. Current Opinion in Electrochemistry, 22, 203-210
Weiß, L. J., Rinklin, P., and Wolfrum, B.
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(2021). Engineering Electrostatic Repulsion of Metal Nanoparticles for Reduced Adsorption in Single-Impact Electrochemical Recordings. ACS Applied Nano Materials, 4(8), 8314-8320
Weiß, L. J., Music, E., Rinklin, P., Straumann, L., Grob, L., Mayer, D., and Wolfrum, B.
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(2021). Inkjet-Printed and Electroplated 3D Electrodes for Recording Extracellular Signals in Cell Culture. Sensors, 21(12), 3981
Grob, L. et al.
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(2022). Single-Impact Electrochemistry in Paper-Based Microfluidics. ACS Sensors, 7 (3), 884-892
Weiß, L. J. et al.
