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At the forefront of scientific exploration, electrochemical sensing is an indispensable and adaptable tool that impacts a diverse range of industries. From life and environmental science to industrial material and food processing, the ability to quantify chemicals can provide greater insight, elevating safety, efficiency and awareness.
In this era of advanced interconnected technology, the significance of low power and highly accurate electrochemical sensors cannot be overstated. In our homes, connected devices allow us to monitor the quality of our air, water, and soil for our plants.
Across the industry, there is even greater demand. Smart medical devices, including wearables, move healthcare into the 21st century by providing real-time continuous monitoring of patient vital signs both inside and outside of clinical facilities, improving insight and increasing quality of care.
Similarly, the expanse of Industry 4.0 in manufacturing and industrial automation has seen many sectors deploy extensive networks of sensing nodes in order to improve their efficiency and safety. Sensors can monitor toxic gasses created during various industrial processes and enable feedback systems in industrial equipment. In food processing, the detection of spoilage and allergenic substances is essential—electrochemical sensors can help to automate pre-cooking taste verification, reporting pH levels and detecting histamines.
Whether it’s monitoring glucose levels in diabetic patients, assessing environmental pollutants, ensuring food safety, or characterizing materials at the atomic level, electrochemical sensors play a pivotal role in advancing scientific knowledge and improving our quality of life.
This article will explore the principles that support electrochemical sensing, the requirements for effective sensor performance, how an analog front-end (AFE) device can be a bridge for current measurement and analysis and delve into specific examples of how these sensors are utilized in medical, environmental, food, and material science applications.
Electrochemical sensor requirements
The typical setup for an electrochemical sensor in electronic engineering involves a three-electrode system, an arrangement seen across many other sensor types (Figure 1).
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Figure 1 Two diagrams indicate the construction of a typical electrochemical sensor. Source: onsemi
Within the sensor, there is a substrate surface material which acts as a protective layer for the sensing electrode. This material’s primary function is to regulate the quantity of molecules that can access the electrode surface and filter out any undesirable particles that may impact the accuracy of the sensor.
At the core of the sensor are three main parts. The working electrode (WE) is where the electrochemical reaction takes place. As particles impact the WE, a reaction occurs, creating either a loss or gain of electrons, leading to electron flow and the production of current. Maintaining a constant potential at the WE is vital, as it enables accurate measurement of the current generated by redox reactions (Figure 1).
The counter electrode (CE) supplies sufficient current to balance out the redox reactions happening at the WE, creating a complementary pair. While the reference electrode (RE) is employed for measuring the potential of the WE and offering feedback to establish the CE voltage.
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Figure 2 The circuit diagram highlights an electrochemical sensor design. Source: onsemi
The high-side resistance in an electrochemical sensor (Figure 2) is an undesired factor that should be minimized, which can be achieved by positioning the RE near the WE. The current flowing through the lower-side resistance indicates the output of the electrochemical measurement and is therefore used to derive the sensor’s output voltage.
Whether an electrochemical sensor is being used in consumer, healthcare, or industrial applications, there are several key technical requirements set by designers that sensors must meet. Factors like high accuracy and low noise go without saying, but alongside this, electrochemical sensors must allow for simple calibration to help cater for the wide range of applications—as packaging or usage may influence calibration, either immediately or over time.
Moreover, with many electrochemical sensors being deployed in portable or low-power solutions, such as wearable medical technology or industrial technology nodes, there are a number of packaging requirements that must be addressed.
Engineers require solutions that feature low-power operation, thus supporting battery powered applications, and that are miniaturized and flexible, allowing for various sensor configurations and easy system integration. Intelligent pre-processing is another important feature on many engineer’s radars, as it can enable more sophisticated calibration and noise filtering, supporting more accurate data delivery.
Common sensor applications
Electrochemical sensors are extensively utilized for several purposes in life science and healthcare, including in the detection of blood alcohol levels and facilitating continuous glucose monitoring (CGM)—a critical component in the management of diabetes, a chronic illness that affects 1 in 11 people worldwide. The CGM device market is projected to grow at a compound annual growth rate (CAGR) of 9% during 2023 to 2032.
Targeting the latest clinical and portable medical devices, a miniaturized AFE is employed for highly accurate measurement of electrochemical currents. The combination of ultra-low-power consumption, flexible configuration, and small size makes it a compelling solution wherever an electrochemical sensor is used.
Beyond medical sciences, electrochemical sensors are ideal for detecting toxic gasses in industrial applications, or for measuring pollution and air quality in environmental applications. They employ a chemical reaction between the target gas and an electrode, generating an electrical current proportional to the specified gas concentration.
The 20-mm electrochemical sensors are widespread and are available for several toxic gasses, including carbon monoxide, hydrogen sulfide and oxides of nitrogen and sulfur, and allow for simple ‘drop in’ replacement. These sensors are utilized in a diverse array of applications, spanning from air quality sensors in urban settings to smart agricultural applications for monitoring plant growth.
Similarly, electrochemical sensors such as potentiostat or corrosion sensors are crucial in environments such as laboratories, mining operations, and material production. They serve as important tools for providing feedback within production systems and managing hazardous substances, ensuring the safety of the operation.
In search of increased yield and production efficiency, food production has also turned to electrochemical sensors. Here, both handheld portable devices and larger automations are deployed for food quality control, ensuring taste and identifying spoilage, allergens or hazardous chemicals.
Sensor design blueprint
Sensors based on electrochemical measurements are readily available. From healthcare and glucose monitoring to broader environmental applications, these sensors provide a complete solution that is designed to increase reliability, accuracy and improve the user experience of wearables and portable medical devices.
These solutions, for instance, can pair with AFE for continuous electrochemical measurement and Bluetooth Low Energy 5.2 technology-enabled microcontroller. Such integrations play a crucial role in making devices smaller and ensuring long-lasting functionality—a vital factor for battery-powered solutions.
The solution, built around CEM102 AFE and RSL15 microcontroller, is complemented with development support, firmware and software, including iOS and Android demo applications (Figure 3).
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Figure 3 Examples screens display demo applications for iOS and Android platforms. Source: onsemi
There is also a CEM102 evaluation board complete with sample code for setting up and conducting measurements with CEM102, making it easier to begin system development. This combined offering is designed to streamline development and promote greater integration and innovation for the next generation of amperometric sensor technologies.
During operation, the CEM102’s function is to connect the sensor network to the digital processing. It is responsible for conditioning the sensor by applying the necessary signals to the electrodes and ensuring accurate measurement from the sensor network, while the RSL15 connects the sensor to wireless Bluetooth LE networks (Figure 4).
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Figure 4 Here is how the CEM102 + RSL15 combo facilitates a wireless electrochemical sensing solution. Source: onsemi
Advancing scientific research
The precise measurement provided by electrochemical sensors is a critical enabler for advancing scientific knowledge. For example, by carefully examining factors such as glucose levels, researchers can obtain valuable insight into chronic illnesses like diabetes. This knowledge can enhance our understanding and expedite innovation, ultimately benefiting a significant portion of the global population.
In the ever-evolving world of electronics, companies require pioneering solutions that not only redefine expectations but also allow for shorter time to market and increased flexibility to provide scope for new applications. From remote healthcare to environmental monitoring and industrial safety, electrochemical sensors fulfill a diverse range of applications and have a significant impact on society.
And the potential of this versatility extends far beyond current applications. Through manufacturing support and collaboration, electrochemical sensors can contribute to advancing research and enhancing comprehension in the medical field and beyond.
The ongoing development of smart technology, along with complementary technologies such as artificial engineering and machine learning, will drive the growing influence of electrochemical sensors on our lives, resulting in the emergence of new innovations and the effective resolution of many longstanding global challenges.
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Hideo Kondo is product marketing engineer at onsemi’s Analog Mixed-Signal Group.
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