Table 3.

Transducers and their characteristics

Transducers	Principles	Characteristics (pros/cons)
Electrochemical impedance spectroscopy/square wave voltammetry	Use of AC waveform to interrogate the real and imaginary impedance	Sensitive to a variety of targets (e.g., proteins, small molecules, oligonucleotide) Need of improving miniaturization, drift, and fouling, drift, and fouling
Field‐effect transistors	Electrostatic modulation of charge carriers in the conduction channel (semiconductor or semimetal)	Low power consumption, miniaturization, continuous measurement Sensitivity variation under ions in an electrolyte
Quartz crystal microbalances/ cantilevers	The capture of mass variation in a specific area by detecting the changes in the frequency	Sensitive to target detection, continuous measurement Stability/durability/response time and reproducibility
Enhanced surface plasmon resonance	Use of plasmonically active metals responding to changes in the local surrounding environment from a binding event near the metal surface	Label‐free real‐time measurement, low cost, high sensitivity Miniaturization requirements of components (spectrometer, light source)
Colorimetric measurement	Use of colorimetric materials, including color responsive dyes and metal nanoparticles that change their colors in response to biomarkers	Straightforward and cost‐effective Image process required and loss of time resolution