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Through the development of mobile end devices including control and evaluation of data with apps, electrochemical sensor technology has penetrated our everyday life. Electrochemical sensors have the function of making an existing, chemically detectable substance qualitatively or quantitatively determinable by converting it into an electrical signal.
Today, sensor technology can be operated completely unplugged.
How do electrochemical sensors work?
A sensor basically requires two functional units:
- A receptor, which transmits the “chemical information” as energy to the
- transducer, which generates an electrical, usable signal from it. The system to be measured should not be changed during this process.
Through the development of mobile end devices including control and analysis of data with apps, the electrochemical sensor technology has penetrated our everyday life. Today, it can be operated completely unplugged, for example in the following areas:
- Point-of-Care-Testing (POCT: Diagnostics directly at the physician’s or also at home)
- Wearables (sensor systems that can be worn on the body or integrated into clothing, e.g., smartwatches)
- Point-of-Use (PoU, off-grid monitoring of environmental data or e.g., gas detectors on site)
- IoT (Internet of Things) – Smart Home etc.
- and OEM products (Original Equipment Manufacturer: Production of original parts under a third-party label).
Sensor development starts with the search for the appropriate electrochemical reaction and the choice of the electrochemical method. This is followed by miniaturisation and finally the conversion of the proof of principle into a reliable, everyday system that can be manufactured in a cost-effective industrial process.
What are the electrochemical measurement methods?
The three most basic methods are potentiometry, amperometry and impedance measurement, of which there are numerous variants.
|Method||Transducer principle||Measured variable|
|Potentiometry||Energy conversion||Voltage (high impedance)|
|Amperometry + coulometry||Limit current||Current + charge (low impedance)|
|Conductivity/impedance measurement||Resistance||Ohmic or complex resistance|
With a very high impedance (GΩ) voltmeter one measures (almost) currentless the voltage between the sensor electrode and a reference electrode, whose potential always remains quite stable. The only changes of interest are those caused by the interactions of the analyte at the interface between the sensor electrode and the sample solution. The measuring cell must therefore be designed in such a way that all other potentials remain unchanged during the measurement.
With this measuring principle, a direct or alternating voltage is applied to the sensor electrode so that an electrochemical conversion of the analyte can take place. The advantage is that the electrode does not have to be in thermodynamic equilibrium and the response time is therefore very short. The measurement setup can also be miniaturised more easily.
In electrochemical impedance spectroscopy, the redox equilibrium is only slightly disturbed (linear range) by a sinusoidal alternating voltage or current. This can be done over a wide frequency spectrum, whereby the impedance changes characteristically with frequency.
This method is non-destructive and can be used “label-free”, i.e., without an additional element for signal generation (redox reaction, fluorescent molecule, etc.), which is particularly advantageous in biosensor technology.
What applications are there for electrochemical sensors?
Besides the few disadvantages such as limited temperature range or sensitivity to impurities, there are numerous advantages such as
- Low energy consumption
- Robustness, specificity, ease of use
- Fast on-site measurements
- Reasonable price
- Suitable for gases, liquids and solids
- High miniaturisation possible
The advantages lead to a wide range of applications, e.g.,
- In gas sensors (oxygen, carbon dioxide, ozone, etc.)
- In the monitoring of environmental parameters (heavy metals, nitrate, etc.)
- In medical technology (detection of metabolic products, antibiotics, etc.)
- In quality and process control (monitoring of biotechnological growth processes)
- Detection of organic substances such as alcohol, ketones, etc.
Screen-Printed Electrodes (SPEs) for mobile and rapid analysis have become increasingly important. SPEs are disposable electrode strips that can be used on a mass scale due to their easy handling and very low price. Electrochemical sensor devices are also available, into which only the correct SPEs for the target analyte have to be inserted and, for example, a drop of the liquid sample dropped on. These methods are so mature that neither toxic chemicals nor sample preparation are required and even untrained personnel can perform the measurement. Often, the result appears on the smartphone screen in just a few minutes. One of our particularly successful product examples is the Sensit Smart by PalmSens.
For electrochemical sensor development, it is extremely important to understand the interplay of all electronic components and the underlying reactions - in other words, electrochemistry.
Since research can draw from the almost infinite supply of chemical reactions, new electrochemical sensor principles are also being discovered and developed. In addition, there are the countless potentials of nanostructuring of electrodes. For this basic research, numerous electroanalytical methods are initially applied: Cyclo-voltammetry, chrono-coulometry, impedance spectroscopy, etc., in order to finally establish a measurement protocol for a dedicated sensor that is as simplified as possible and suitable for practical use. Often, very small currents in the nA or pA range have to be measurable.
Such highest requirements are met in our product portfolio by the potentiostats/galvanostats by PalmSens and Ivium. These instruments are capable of all electroanalytical methods and are designed for impedance measurements with high precision over a wide frequency range.
Specially for education, PalmSens offers an “Educational Kit” as well as compact and very affordable instruments in the EmStat series. Palmsens has been committed to sensor development from the beginning and is now a leader in miniaturised, portable devices with additional functions such as Bluetooth or screen-printed electrodes, e.g., the PalmSens4 with Sensit Smart.
For high-throughput testing, e.g., to optimise materials and measurement parameters, we offer a comprehensive range of multi-channel solutions: Multiplexers, poly-potentiostats, multi-channel potentiostats/galvanostats, etc.
In our online shop you will also find a wide range of different electrode types, electrochemical cells and accessories.
EKTechnologies is, after almost 30 years of partnership with numerous research institutions and major industrial players, your expert for questions around electrochemical sensor development.
A special challenge is always the transfer of the proof of principle into a market-ready application. We accompany and support you all the way with the best solutions and competent advice!