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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.


Related in: MedlinePlus

Influence from sensor size on incident flux in a system with diffusion limited binding from stagnant liquids. The arrows show the directions of the analyte flux, assuming that nothing binds outside the active sensor region. The planar infinite surface in (A) gives the lowest average incident flux. If the spot is smaller, as in (B), the binding rate will become higher, especially at the edges. The binding rate is also higher in (C), showing a one dimensional sensor, which gives an incident flux with cylindrical symmetry. The highest average flux to the active area occurs for radial symmetry and a point-like sensor, as shown in (D).
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f2-sensors-12-03018: Influence from sensor size on incident flux in a system with diffusion limited binding from stagnant liquids. The arrows show the directions of the analyte flux, assuming that nothing binds outside the active sensor region. The planar infinite surface in (A) gives the lowest average incident flux. If the spot is smaller, as in (B), the binding rate will become higher, especially at the edges. The binding rate is also higher in (C), showing a one dimensional sensor, which gives an incident flux with cylindrical symmetry. The highest average flux to the active area occurs for radial symmetry and a point-like sensor, as shown in (D).

Mentions: Although only approximate analytical solutions are available for diffusive flux to other sensor geometries, it is clear that the infinite surface geometry provides the lowest flux of molecules to the sensor [23]. Therefore, smaller sensor spots will tend to cause an increased flux into A due to the edges [20]. The increased flux associated with smaller sensors is conceptually illustrated in Figure 2 for different architectures. When diffusion determines binding rate, the smaller sensors will result in higher ∂Γ/∂t because their geometry induces increased flux at the borders. One can also think of this phenomenon as an effect of sensor dimensionality: Equation (3) represents the slowest type of binding because the depletion zone only grows in one dimension, but “wires” or “dots” have depletion zones that grow in two or three dimensions [23]. For the one dimensional problem [Equation (3)], the depletion zone at the sensor has a characteristic thickness determined by the independent Brownian motion of the molecules:(4)z¯=2Dt


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

Dahlin AB - Sensors (Basel) (2012)

Influence from sensor size on incident flux in a system with diffusion limited binding from stagnant liquids. The arrows show the directions of the analyte flux, assuming that nothing binds outside the active sensor region. The planar infinite surface in (A) gives the lowest average incident flux. If the spot is smaller, as in (B), the binding rate will become higher, especially at the edges. The binding rate is also higher in (C), showing a one dimensional sensor, which gives an incident flux with cylindrical symmetry. The highest average flux to the active area occurs for radial symmetry and a point-like sensor, as shown in (D).
© Copyright Policy
Related In: Results  -  Collection

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

f2-sensors-12-03018: Influence from sensor size on incident flux in a system with diffusion limited binding from stagnant liquids. The arrows show the directions of the analyte flux, assuming that nothing binds outside the active sensor region. The planar infinite surface in (A) gives the lowest average incident flux. If the spot is smaller, as in (B), the binding rate will become higher, especially at the edges. The binding rate is also higher in (C), showing a one dimensional sensor, which gives an incident flux with cylindrical symmetry. The highest average flux to the active area occurs for radial symmetry and a point-like sensor, as shown in (D).
Mentions: Although only approximate analytical solutions are available for diffusive flux to other sensor geometries, it is clear that the infinite surface geometry provides the lowest flux of molecules to the sensor [23]. Therefore, smaller sensor spots will tend to cause an increased flux into A due to the edges [20]. The increased flux associated with smaller sensors is conceptually illustrated in Figure 2 for different architectures. When diffusion determines binding rate, the smaller sensors will result in higher ∂Γ/∂t because their geometry induces increased flux at the borders. One can also think of this phenomenon as an effect of sensor dimensionality: Equation (3) represents the slowest type of binding because the depletion zone only grows in one dimension, but “wires” or “dots” have depletion zones that grow in two or three dimensions [23]. For the one dimensional problem [Equation (3)], the depletion zone at the sensor has a characteristic thickness determined by the independent Brownian motion of the molecules:(4)z¯=2Dt

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.


Related in: MedlinePlus