In 1999, researchers at the Georgia Institute of Technology created an unusual type of sensor capable of measuring the mass of very small particles. The sensing element of their device essentially consisted of a single carbon nanotube: by attaching a particle to the end of the nanotube and measuring the change in its vibrational frequency, researchers were able to determine the particle’s mass.
This sensor was one of the earliest examples of a synthetic nanosensor: a device capable of measuring the physical changes that accompany nanoscale processes and converting these into signals that can be analyzed.
Nanosensors, however, are not new. Living organisms have long used an array of biological nanosensors – such as enzymes, antibodies, and DNA – to accomplish a wide range of tasks, including information storage and monitoring of metabolic processes.
Artificial nanosensors, which are created in the lab, in many ways aim to replicate the performance of these “biological” nanosensors (indeed, many nanosensors are directly inspired by biological systems). By harnessing the power of molecular machinery, nanosensors offer radically different performance to conventional macro-scale sensors. Often, nanosensors are used to detect the presence of certain chemical species or nanoparticles, while others may monitor physical parameters such as temperature or mechanical strain at the nanoscale.
Research into nanosensors has accelerated over the last two decades, and a huge array of different nanosensor technologies have been developed. Most of these can be roughly categorized into three groups: mechanical or vibrational nanosensors, optical nanosensors, electromagnetic nanosensors.
Mechanical/vibrational nanosensors often consist of resonating carbon nanotubes (CNTs). The extremely high resonant frequency of these structures, typically in the GHz region, allows the detection of very small changes in mass. This offers the possibility of using such technologies to build gas and chemical sensors with extremely high levels of sensitivity.
Optical nanosensors are those which transmit a signal optically. At their simplest, an optical nanosensor can consist of a single fluorescent dye molecule which preferentially binds to certain molecular sites (for example, inside a cell). Other optical nanosensor designs include fiber optic probes. Optical nanosensors enable identification and quantification of disease biomarkers, small molecule proteins and peptides; facilitating analysis of biological processes in vivo.
Electromagnetic nanosensors are capable of detecting analytes bonded to a structure by measuring current enhancement or inhibition that arises as a result of analyte binding. For example, gold nanoparticles undergo a change in their electron transport behavior when hydrogen sulfide molecules adsorb to their surface, enabling very sensitive detection of hydrogen sulfide.
Other emerging nanosensor technologies include nanowire-based thermal probes and polymer vesicle-based sensors.
As well as exhibiting extremely high selectivity and sensitivity, nanosensor-based solutions are anticipated to have low production costs. This opens the door to a huge range of applications including medical diagnostics, environmental sensing, food safety, and defense. If you would like to keep up to date with the latest innovations in this area, simply contact a member of the team to join our mailing list.
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