- Electrical impedance sensing is a label-free analytical technique that measures the opposition of a biological or chemical system to the flow of an alternating current (AC).
- By analyzing how electrical impedance changes in response to molecular interactions, cellular events, or material properties, this method enables researchers to monitor dynamic biological processes in real time with high sensitivity. Electrical impedance sensing is widely used in fields such as cell biology, drug screening, diagnostics, and material characterization, offering a non-invasive and scalable way to study complex systems.
- At its core, electrical impedance is the combination of resistance and reactance (capacitive and inductive elements) that a system presents to an AC signal. In electrical impedance sensing, electrodes are placed within or near the system of interest—such as a cell culture, biosensor surface, or microfluidic device—and an AC voltage is applied. The resulting current is measured, and the impedance is calculated as a function of frequency and time. As biological or chemical changes occur, such as cell adhesion, growth, barrier formation, or molecular binding, they alter the electrical properties of the system, leading to measurable impedance shifts.
- One of the most common applications of electrical impedance sensing is in real-time cell analysis. In such assays, cells are cultured on electrode-coated surfaces. As the cells adhere, spread, proliferate, or respond to stimuli, they modify the current pathway, which translates into impedance changes. This allows continuous, label-free monitoring of cellular behavior—including proliferation, cytotoxicity, migration, and morphological changes—without the need for dyes or destructive sampling. Technologies like xCELLigence and ECIS (Electric Cell-substrate Impedance Sensing) platforms have made this approach a standard tool in pharmacology and toxicology.
- Another major application area is biosensing, where electrical impedance spectroscopy (EIS) is used to detect biomolecular interactions such as antibody–antigen binding, DNA hybridization, or protein–ligand interactions. In these systems, a recognition layer (e.g., an immobilized receptor or antibody) is placed on the sensor surface. When the target analyte binds to the surface, it causes changes in the dielectric properties or surface conductivity, which in turn shifts the impedance signal. This method is particularly useful in point-of-care diagnostics and environmental monitoring due to its sensitivity, portability, and compatibility with miniaturized, label-free formats.
- Electrical impedance sensing also plays an important role in material science and electrochemistry, where it is used to characterize coatings, corrosion, and electrode interfaces. The technique provides insight into charge transfer processes, surface roughness, and the formation of insulating or conductive films. In tissue engineering and regenerative medicine, it is used to assess tissue integrity, barrier function (e.g., in epithelial or endothelial models), and scaffold-cell interactions.
- One of the main advantages of electrical impedance sensing is its real-time, continuous measurement capability without requiring external labels or reporters. It is non-destructive and can be applied in a high-throughput manner, making it ideal for long-term studies and kinetic analysis. Additionally, it is compatible with microfluidic systems and lab-on-a-chip devices, further extending its utility in miniaturized and automated platforms.
- However, interpreting impedance data can be complex, as the signal depends on multiple parameters including cell morphology, electrode geometry, medium conductivity, and frequency. Accurate modeling and calibration are necessary to extract meaningful biological information. Furthermore, sensitivity can vary depending on the target and setup, particularly when dealing with very small molecules or low-abundance targets.
