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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.


The principle of a surface-based sensor system operating in vitro. On the active area A there are recognition elements for the target analyte, which has molecular weight M and is present in a sample of volume V at concentration C. The sample solution is introduced to the surface in a channel with height h, possibly with continuous flow at an average velocity v. The maximum surface coverage of the analyte Γmax is defined by the number of receptors (and M implicitly).
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f1-sensors-12-03018: The principle of a surface-based sensor system operating in vitro. On the active area A there are recognition elements for the target analyte, which has molecular weight M and is present in a sample of volume V at concentration C. The sample solution is introduced to the surface in a channel with height h, possibly with continuous flow at an average velocity v. The maximum surface coverage of the analyte Γmax is defined by the number of receptors (and M implicitly).

Mentions: I will start by going through the common advantages of sensor miniaturization and evaluate to what extent they really enhance sensor performance (direct problems with miniaturization are discussed in the next section.). Consider the system in Figure 1. The subject of miniaturization concerns the sensor active area A, where analyte binding occurs and generates a signal. The sensor surface is exposed to a sample with volume V, in which we find the analyte present at a (molar) concentration C. The number of molecules available is then VC and the mass of analyte available is VCM, where M is the molecular mass. The sensor operates by transducing molecular adsorption on A into a detectable signal that increases (usually linearly) with the surface coverage Γ (mass per unit area). As a result of surface functionalization, there will be a certain number of binding sites available on A and there is a defined maximum surface coverage Γmax. Increasing Γmax is one strategy to improve the performance of any surface-based sensor, but surface chemistry is not directly related to the miniaturization issue and will thus not be discussed further. Instead, I will here consider the consequences of the chosen size of A, especially in relation to V, C and M. For one thing I will show that the research field would likely benefit much from thinking more in terms of concentration instead of number of molecules. As will be shown, the quantity that determines Γ is normally C, while V does not come into play even for relatively large A.


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

Dahlin AB - Sensors (Basel) (2012)

The principle of a surface-based sensor system operating in vitro. On the active area A there are recognition elements for the target analyte, which has molecular weight M and is present in a sample of volume V at concentration C. The sample solution is introduced to the surface in a channel with height h, possibly with continuous flow at an average velocity v. The maximum surface coverage of the analyte Γmax is defined by the number of receptors (and M implicitly).
© Copyright Policy
Related In: Results  -  Collection

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

f1-sensors-12-03018: The principle of a surface-based sensor system operating in vitro. On the active area A there are recognition elements for the target analyte, which has molecular weight M and is present in a sample of volume V at concentration C. The sample solution is introduced to the surface in a channel with height h, possibly with continuous flow at an average velocity v. The maximum surface coverage of the analyte Γmax is defined by the number of receptors (and M implicitly).
Mentions: I will start by going through the common advantages of sensor miniaturization and evaluate to what extent they really enhance sensor performance (direct problems with miniaturization are discussed in the next section.). Consider the system in Figure 1. The subject of miniaturization concerns the sensor active area A, where analyte binding occurs and generates a signal. The sensor surface is exposed to a sample with volume V, in which we find the analyte present at a (molar) concentration C. The number of molecules available is then VC and the mass of analyte available is VCM, where M is the molecular mass. The sensor operates by transducing molecular adsorption on A into a detectable signal that increases (usually linearly) with the surface coverage Γ (mass per unit area). As a result of surface functionalization, there will be a certain number of binding sites available on A and there is a defined maximum surface coverage Γmax. Increasing Γmax is one strategy to improve the performance of any surface-based sensor, but surface chemistry is not directly related to the miniaturization issue and will thus not be discussed further. Instead, I will here consider the consequences of the chosen size of A, especially in relation to V, C and M. For one thing I will show that the research field would likely benefit much from thinking more in terms of concentration instead of number of molecules. As will be shown, the quantity that determines Γ is normally C, while V does not come into play even for relatively large A.

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.