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Peter Grünberg Institute / Institute of Complex Systems

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On-chip electrochemical techniques

We are investigating chip-based electrochemical techniques for real-time detection of biomolecules such as neurotransmitters. One of our most sensitive approaches is based on nanoscaled redox cycling, the repetitive oxidation and reduction of molecules between two closely spaced electrodes, which amplifies the electrochemical signal by orders of magnitudes.

On-chip detection of neurotransmitter release from  stimulated PC12 cells

On-chip detection of neurotransmitter release

We develop real-time on-chip electrochemical approaches to detect electroactive neurotransmitters in vitro.  The measurement system consists of a biocompatible array of 64 metal microelectrodes and a highly sensitive multichannel amplifier. Cells can be cultured on-chip for many weeks and single-vesicle release events can be detected amperometrically. The system can be potentially utilized for high-throughput pharmacological screening of drugs.

Redox cycling principle

Redox Cycling Principle

Redox-cycling sensors feature two closely-spaced electrodes that can be individually biased to different potentials. Driven by diffusion, redox-active molecules can undergo repeated redox-reaction at appropriately biased electrodes, thus generating an electrical current. The current is proportional to the number of molecules participating in redox cycling and inverse proportional to the time it takes for a molecule to diffuse from one electrode to the other.

Sensor design

Sensor Design

Nanocavity redox-cycling sensors allow confined redox cycling of molecules inside a nanocavity between the electrodes. Fast diffusion on the nanometer scale results in very high redox cycling efficiencies, which amplify the electrochemical current by orders of magnitude.

Redox cycling efficiency

Redox cycling efficiency

The high cycling efficiency of nanocavity sensors is demonstrated by the almost exact match of oxidative and reductive currents obtained during cyclic voltammetry. Beside their application in cell-chip interfaces, nanocavity redox-cycling sensors can also be used in a widespread field of electrochemical applications. Since the redox-cycling effect allows an enormous signal amplification at small inter-electrode distances, ultra-sensitive electrochemical measurements can be performed at high spatial resolution.

Nanocavity sensor array

Nanocavity sensor array

On-chip electrochemical recordings from cellular networks require sensing devices that feature a high spatiotemporal resolution. In order to proof the capabilities of arrays of nanocavity redox cycling sensors, chips are incorporated into microfluidic devices that allow to generate rapidly changing concentration gradients, which can be detected by the sensor array.

Disposable system for recording neurotransmitter release from individual cells in vitro

Printed electrochemical devices

We investigate disposable systems for recording neurotransmitter release from individual cells in vitro. Microelectrodes are fabricated using a process based on screen-printed carbon paste. Our approach allows rapid fabrication of devices at low costs without standard clean-room technology. The printed microelectrodes are utilized for real-time observation of vesicle release from cells.

Additional Information


Jun.-Prof. Dr. Bernhard Wolfrum

Tel.:  +49-2461-61-3285


Y. Liu, B. Wolfrum, M. Hüske, A. Offenhäusser, E. Wang, and D. Mayer: Transistor Functions Based on Electrochemical Rectification. Angewandte Chemie Int. Ed., 52, 4029-4032 (2013)


P.S. Singh, E. Kätelhön, K. Mathwig, B. Wolfrum, and S.G. Lemay:

Stochasticity in Single-Molecule Nanoelectrochemistry: Origins, Consequences, and Solutions. ACS Nano, 6 (11) 9662-9671 (2012)


A. Yakushenko, J. Schnitker, and B. Wolfrum: Printed Carbon Microelectrodes for Electrochemical Detection of Single Vesicle Release from PC12 Cells. Analytical Chemistry, 84(10), 4613-4617 (2012)


E. Kätelhön and B. Wolfrum: On-chip redox cycling techniques for electrochemical detection. Reviews in Analytical Chemistry, , 7-14 31(2012)


E. Kätelhön and B. Wolfrum: Simulation-based investigations on noise characteristics of redox-cycling sensors. Physica Status Solidi, 5 (2012)


M.A.G. Zevenbergen; P.S. Singh; E.D. Goluch; B.L. Wolfrum; S.G. Lemay: Stochastic Sensing of Single Molecules in a Nanofluidic Electrochemical Device. Nano Letters, 11, 2881-2886 (2011)


E. Kätelhön, B. Hofmann, S.G. Lemay, M.A.G. Zevenbergen, A. Offenhäusser, and B. Wolfrum: Nanocavity Redox Cycling Sensors for the Detection of Dopamine Fluctuations in Microfluidic Gradients, Analytical Chemistry, 82 , 8502–8509 (2010)


E. Kätelhön, B. Hofmann, M. Banzet, A. Offenhäusser, and B. Wolfrum: Time-resolved mapping of neurotransmitter fluctuations by arrays of nanocavity redox-cycling sensors , E. Kätelhön, B. Hofmann, M. Banzet, A. Offenhäusser, and B. Wolfrum, Procedia Engineering, 5, 956-958, (2010)


M.A.G. Zevenbergen, B.L. Wolfrum, E.D. Goluch, P.S. Singh, S.G. Lemay: Fast electron-transfer kinetics probed in nanofluidic channels. JACS, 131, 11471-11477 (2009)


B. Wolfrum, M.A.G. Zevenbergen, and S.G. Lemay: Nanofluidic redox-cycling amplification for the selective detection of catechol. Analytical Chemistry, 80, 972-977 (2008)