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Size matters: problems and advantages associated with highly miniaturized sensors.

Dahlin AB - Sensors (Basel) (2012)

Bottom Line: Still, all issues discussed are generic in the sense that the conclusions apply to practically all types of surface sensitive techniques.Instead, it is suggested that sensing on the microscale often offers a good compromise between utilizing some possible advantages of miniaturization while avoiding the complications.This means that ensemble measurements on multiple nanoscale sensors are preferable instead of utilizing a single transducer entity.

View Article: PubMed Central - PubMed

Affiliation: Division of Bionanophotonics, Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden. adahlin@chalmers.se

ABSTRACT
There is no doubt that the recent advances in nanotechnology have made it possible to realize a great variety of new sensors with signal transduction mechanisms utilizing physical phenomena at the nanoscale. Some examples are conductivity measurements in nanowires, deflection of cantilevers and spectroscopy of plasmonic nanoparticles. The fact that these techniques are based on the special properties of nanostructural entities provides for extreme sensor miniaturization since a single structural unit often can be used as transducer. This review discusses the advantages and problems with such small sensors, with focus on biosensing applications and label-free real-time analysis of liquid samples. Many aspects of sensor design are considered, such as thermodynamic and diffusion aspects on binding kinetics as well as multiplexing and noise issues. Still, all issues discussed are generic in the sense that the conclusions apply to practically all types of surface sensitive techniques. As a counterweight to the current research trend, it is argued that in many real world applications, better performance is achieved if the active sensor is larger than that in typical nanosensors. Although there are certain specific sensing applications where nanoscale transducers are necessary, it is argued herein that this represents a relatively rare situation. Instead, it is suggested that sensing on the microscale often offers a good compromise between utilizing some possible advantages of miniaturization while avoiding the complications. This means that ensemble measurements on multiple nanoscale sensors are preferable instead of utilizing a single transducer entity.

No MeSH data available.


Example of stability differences when performing microspectroscopy on areas of different size (10 × 50 or 2 × 10 μm). The sensor output parameter is the resonance wavelength of plasmonic gold nanodisks on the surface (in nm). The baseline of the idle system is monitored in (A) showing the same short-term noise for both A, but improved stability for the higher A. The change in sensor parameter between two acquisitions as a function of the temporal resolution and the elapsed time between the acquisitions is shown in (B). The arrow and circle indicate the lowest noise for the smaller and larger A respectively. Reproduced with permission from Reference [15] (Copyright 2009 American Chemical Society).
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f5-sensors-12-03018: Example of stability differences when performing microspectroscopy on areas of different size (10 × 50 or 2 × 10 μm). The sensor output parameter is the resonance wavelength of plasmonic gold nanodisks on the surface (in nm). The baseline of the idle system is monitored in (A) showing the same short-term noise for both A, but improved stability for the higher A. The change in sensor parameter between two acquisitions as a function of the temporal resolution and the elapsed time between the acquisitions is shown in (B). The arrow and circle indicate the lowest noise for the smaller and larger A respectively. Reproduced with permission from Reference [15] (Copyright 2009 American Chemical Society).

Mentions: When it comes to stability issues, there are some studies performed on optical sensors showing that mechanical stability often becomes a problem for small sensors. For instance, it has been shown that the resolution in single nanoparticle spectroscopy suffers heavily from small changes in position of the particle with respect to the surrounding optical components [42]. Another example is given in Figure 5(A), which shows an example from transmission mode spectroscopy on the microscale. Two differently sized areas are probed and the sensor output parameter (here resonance wavelength) is monitored when the system is idle. For A = 10 × 50 μm, the baseline is relatively stable while for A = 2 × 10 μm there are clear stability problems and additional fluctuations occur on a timescale of ∼1 min even though the noise level is the same (on the short timescale). This is further illustrated in Figure 5(B), which shows the differential of two sensor readouts as a function of number of averages and time elapsed between the readouts. Although the same noise is observed for both values of A at the highest temporal resolution, a lower noise level is possible for the higher A though averaging while the stability problems associated with the smaller A hinders noise reduction. The improved stability for larger A was attributed to small movements of the surface in relation to the optical setup [15]. Over very short time periods, the same noise was observed for both A because in this particular case I was limited by the detector dynamic range. Of course, this single example does not say much but about the general stability of nanosensors compared to their larger counterparts. Most likely, one can achieve good stability also for miniaturized sensors, but it seems fair to say that smaller sensors will tend to become less robust. They will likely require a more controlled environment and complicated experimental setup.


Size matters: problems and advantages associated with highly miniaturized sensors.

Dahlin AB - Sensors (Basel) (2012)

Example of stability differences when performing microspectroscopy on areas of different size (10 × 50 or 2 × 10 μm). The sensor output parameter is the resonance wavelength of plasmonic gold nanodisks on the surface (in nm). The baseline of the idle system is monitored in (A) showing the same short-term noise for both A, but improved stability for the higher A. The change in sensor parameter between two acquisitions as a function of the temporal resolution and the elapsed time between the acquisitions is shown in (B). The arrow and circle indicate the lowest noise for the smaller and larger A respectively. Reproduced with permission from Reference [15] (Copyright 2009 American Chemical Society).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376590&req=5

f5-sensors-12-03018: Example of stability differences when performing microspectroscopy on areas of different size (10 × 50 or 2 × 10 μm). The sensor output parameter is the resonance wavelength of plasmonic gold nanodisks on the surface (in nm). The baseline of the idle system is monitored in (A) showing the same short-term noise for both A, but improved stability for the higher A. The change in sensor parameter between two acquisitions as a function of the temporal resolution and the elapsed time between the acquisitions is shown in (B). The arrow and circle indicate the lowest noise for the smaller and larger A respectively. Reproduced with permission from Reference [15] (Copyright 2009 American Chemical Society).
Mentions: When it comes to stability issues, there are some studies performed on optical sensors showing that mechanical stability often becomes a problem for small sensors. For instance, it has been shown that the resolution in single nanoparticle spectroscopy suffers heavily from small changes in position of the particle with respect to the surrounding optical components [42]. Another example is given in Figure 5(A), which shows an example from transmission mode spectroscopy on the microscale. Two differently sized areas are probed and the sensor output parameter (here resonance wavelength) is monitored when the system is idle. For A = 10 × 50 μm, the baseline is relatively stable while for A = 2 × 10 μm there are clear stability problems and additional fluctuations occur on a timescale of ∼1 min even though the noise level is the same (on the short timescale). This is further illustrated in Figure 5(B), which shows the differential of two sensor readouts as a function of number of averages and time elapsed between the readouts. Although the same noise is observed for both values of A at the highest temporal resolution, a lower noise level is possible for the higher A though averaging while the stability problems associated with the smaller A hinders noise reduction. The improved stability for larger A was attributed to small movements of the surface in relation to the optical setup [15]. Over very short time periods, the same noise was observed for both A because in this particular case I was limited by the detector dynamic range. Of course, this single example does not say much but about the general stability of nanosensors compared to their larger counterparts. Most likely, one can achieve good stability also for miniaturized sensors, but it seems fair to say that smaller sensors will tend to become less robust. They will likely require a more controlled environment and complicated experimental setup.

Bottom Line: Still, all issues discussed are generic in the sense that the conclusions apply to practically all types of surface sensitive techniques.Instead, it is suggested that sensing on the microscale often offers a good compromise between utilizing some possible advantages of miniaturization while avoiding the complications.This means that ensemble measurements on multiple nanoscale sensors are preferable instead of utilizing a single transducer entity.

View Article: PubMed Central - PubMed

Affiliation: Division of Bionanophotonics, Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden. adahlin@chalmers.se

ABSTRACT
There is no doubt that the recent advances in nanotechnology have made it possible to realize a great variety of new sensors with signal transduction mechanisms utilizing physical phenomena at the nanoscale. Some examples are conductivity measurements in nanowires, deflection of cantilevers and spectroscopy of plasmonic nanoparticles. The fact that these techniques are based on the special properties of nanostructural entities provides for extreme sensor miniaturization since a single structural unit often can be used as transducer. This review discusses the advantages and problems with such small sensors, with focus on biosensing applications and label-free real-time analysis of liquid samples. Many aspects of sensor design are considered, such as thermodynamic and diffusion aspects on binding kinetics as well as multiplexing and noise issues. Still, all issues discussed are generic in the sense that the conclusions apply to practically all types of surface sensitive techniques. As a counterweight to the current research trend, it is argued that in many real world applications, better performance is achieved if the active sensor is larger than that in typical nanosensors. Although there are certain specific sensing applications where nanoscale transducers are necessary, it is argued herein that this represents a relatively rare situation. Instead, it is suggested that sensing on the microscale often offers a good compromise between utilizing some possible advantages of miniaturization while avoiding the complications. This means that ensemble measurements on multiple nanoscale sensors are preferable instead of utilizing a single transducer entity.

No MeSH data available.