The two most-common signal-transduction methods are optical and electrochemical, and their various subgroups. Optical methods still dominate diagnostic measurements, but they have one major drawback – the measurement must be carried out in a “clean” sample, which invariably requires the removal of cellular material. The use of radioactive tracers was common in the past but less so now. There has been a flurry of interest in recent years in magnetic signal generation, but this has yet to be fully established in commercial products.
What alternative signal transduction methods are emerging for the measurement of clinically relevant parameters in biological samples, and which of these are important for use at the point-of-care (POC)?
Piezoelectric and pyroelectric signal-transduction methods are used in numerous applications outside of diagnostics, including motion sensors, accelerometers, pressure sensors, and compact disc players. Pyroelectric methods are mainly used for sensing, whereas piezoelectric methods can be used in both sensors and actuators.
The great benefit of the piezoelectric and pyroelectric effects is that they are direct methods for converting energy from one form to another. This means the mechanical or thermal event is converted directly into an electrical signal, without the need for an intermediate step.
There are three main signal transduction methods in which the measurement method involves mechanical parameters: Quartz crystal microbalance (QCM) and associated technologies, surface acoustic wave (SAW) technologies, and methods using microcantilevers. (The Figure shows a typical quartz resonator used in some of these applications.)
This article focuses on technologies based on the piezo- and pyroelectric effects, such as detection methods that rely on measurement of thermal or mechanical effects. The more relevant methods are highlighted, with a focus on a novel method for homogeneous assays using a pyro-optical method that can deliver lab-quality results in minutes.
To read the article, which originally appeared at our sibling publication Medical Electronics Design, and which includes numerous references, click here.
About the author
Steve Ross is director of R&D at Vivacta Limited (Sittingbourne, Kent, UK).
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