Dielectric Spectroscopy: Revealing the True Colors of Biological Matter

Abstract

Accurate characterization of biological matter, for example, in tissue, cells, and biological fluids, is of high importance. For example, early and correct detection of abnormalities, such as cancer, is essential as it enables early and effective type-specific treatment, which is crucial for mortality reduction [1]. Moreover, it is imperative to investigate the effectiveness and toxicity of pharmaceutical treatments before administration in clinical practice [2]. However, biological matter characterization still faces many challenges. State-of-the-art imaging and characterization methods have drawbacks, such as the requirement to attach difficult-to-find and costly labels to the biological target (e.g., COVID-19 rapid test), expensive equipment (e.g., magnetic resonance imaging or MRI), low accuracy (e.g., ultrasound), use of ionizing radiation (e.g., X-rays), and invasiveness [3]. The characterization of biological matter using microwave (µW), millimeter wave (mmW), and Terahertz (THz) spectroscopy is a promising alternative: it is label-free, does not require ionizing radiation, and can be non-invasive.Moreover, there is a significant difference in how different biological materials absorb, reflect, and transmit electromagnetic (EM) waves [4] that is due to the difference in their dielectric properties. The dielectric properties are described by the frequency-dependent material parameter called the complex permittivity 𝜺(𝒇), which expresses how the material

Microwave Devices for Wearable Sensors and IoT

“…Indeed, the majority of these passive RF or microwave-activated microfluidic wearable sensors are based on dielectric spectroscopy, which has been found to be a label-free and noninvasive technique for analyzing biological substances for different purposes (from fluid identification to cancer cell detection), as extensively described in [41].…”

Simple Semianalytical Septum Design for Improved Matching in Open TEM Cells

“…As TEM cells are easy to build and low-cost, they are used in a wide variety of applications. For instance, they are successfully used for dielectric characterizations [1], [2] in [3], for biological cell exposure in [4], and for EMC/EMI pre-compliance tests in [5], [6].…”

Microwave Resonators Enhanced With 3D Liquid-Metal Electrodes for Microparticle Sensing in Microfluidic Applications

“…In resistive pulse sensing technique, which operates at low AC frequencies, an insulating microparticle partially blocks the ionic current between the electrodes and increases the resistance across them. For capacitive sensors which operate at low ion concentrations and/or high frequencies, e.g., microwave band [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], the particle modifies the capacitance of the sensor in proportion to the square of the electric field it experiences in the sensing region. For capacitive sensors, changes induced by particles can be measured with high precision if the sensor is configured as a resonator: this way an impedance change translates into a shift in the resonator's phase, amplitude or frequency, which can then be measured by phase-sensitive detection.…”