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Flow-induced voltage generation over monolayer graphene in the presence of herringbone grooves.

Lee SH, Kang YB, Jung W, Jung Y, Kim S, Noh HM - Nanoscale Res Lett (2013)

Bottom Line: Phys.We found that the flow-induced voltage decreased significantly in the presence of herringbone grooves in both parallel and perpendicular alignments.These results support our previous interpretation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea. soohyun@kaist.ac.kr.

ABSTRACT
While flow-induced voltage over a graphene layer has been reported, its origin remains unclear. In our previous study, we suggested different mechanisms for different experimental configurations: phonon dragging effect for the parallel alignment and an enhanced out-of-plane phonon mode for the perpendicular alignment (Appl. Phys. Lett. 102:063116, 2011). In order to further examine the origin of flow-induced voltage, we introduced a transverse flow component by integrating staggered herringbone grooves in the microchannel. We found that the flow-induced voltage decreased significantly in the presence of herringbone grooves in both parallel and perpendicular alignments. These results support our previous interpretation.

No MeSH data available.


Related in: MedlinePlus

Simulated and measured mixing performance. (a) Simulated mixing performance in the absence of herringbone grooves. (b) Simulated mixing performance in the presence of herringbone grooves. (c) Actual mixing result in the absence of herringbone grooves. (d) Actual mixing result in the presence of herringbone grooves. (e) Coefficient of variation with and without herringbone grooves at a flow rate of 100 μL/min.
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Figure 2: Simulated and measured mixing performance. (a) Simulated mixing performance in the absence of herringbone grooves. (b) Simulated mixing performance in the presence of herringbone grooves. (c) Actual mixing result in the absence of herringbone grooves. (d) Actual mixing result in the presence of herringbone grooves. (e) Coefficient of variation with and without herringbone grooves at a flow rate of 100 μL/min.

Mentions: Prior to measuring flow-induced voltage, we investigated the mixing performance of the herringbone grooves. Figure 2a,b shows the simulation results of mixing between pure water and dyed water without and with herringbone grooves, respectively. A 3-D numerical simulation was performed using COMSOL Multiphysics (ver. 4.3a). The simulation geometry was identical to the actual microchannel device. Figure 2c,d shows the actual experimental data. Two streams of liquid (pure water and red dyed water) were injected into the microchannel via two inlets using a syringe pump. In the absence of herringbone grooves, only a minimal amount of mixing due to thermal diffusion was observed at the outlet of the channel in both simulated and experimental data. On the other hand, significantly more mixing was observed in the device with herringbone grooves. Mixing performance was also evaluated from the coefficient of variation (CV) [18], which is a normalized measure of dispersion of a probability distribution. The CV of concentration is considered a good measure of mixing quality. A positive value (approximately 1.0) indicates no mixing, and a value of 0 indicates complete mixing. As mixing progressed, the CV decayed exponentially from 1 to 0. We compared the mixing performance of the channels with and without grooves at various flow rates. At a flow rate of 100 μL/min, the channel with grooves (red line) showed better mixing performance (lower CV) than the channel without grooves (blue line in Figure 2e). The number of mixing cycles required for the transition from CV = 1 to CV = 0.1 was reduced from 4 to 2 cycles by the presence of grooves. These mixing results indicate that a transverse flow component was induced by the herringbone grooves.


Flow-induced voltage generation over monolayer graphene in the presence of herringbone grooves.

Lee SH, Kang YB, Jung W, Jung Y, Kim S, Noh HM - Nanoscale Res Lett (2013)

Simulated and measured mixing performance. (a) Simulated mixing performance in the absence of herringbone grooves. (b) Simulated mixing performance in the presence of herringbone grooves. (c) Actual mixing result in the absence of herringbone grooves. (d) Actual mixing result in the presence of herringbone grooves. (e) Coefficient of variation with and without herringbone grooves at a flow rate of 100 μL/min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225506&req=5

Figure 2: Simulated and measured mixing performance. (a) Simulated mixing performance in the absence of herringbone grooves. (b) Simulated mixing performance in the presence of herringbone grooves. (c) Actual mixing result in the absence of herringbone grooves. (d) Actual mixing result in the presence of herringbone grooves. (e) Coefficient of variation with and without herringbone grooves at a flow rate of 100 μL/min.
Mentions: Prior to measuring flow-induced voltage, we investigated the mixing performance of the herringbone grooves. Figure 2a,b shows the simulation results of mixing between pure water and dyed water without and with herringbone grooves, respectively. A 3-D numerical simulation was performed using COMSOL Multiphysics (ver. 4.3a). The simulation geometry was identical to the actual microchannel device. Figure 2c,d shows the actual experimental data. Two streams of liquid (pure water and red dyed water) were injected into the microchannel via two inlets using a syringe pump. In the absence of herringbone grooves, only a minimal amount of mixing due to thermal diffusion was observed at the outlet of the channel in both simulated and experimental data. On the other hand, significantly more mixing was observed in the device with herringbone grooves. Mixing performance was also evaluated from the coefficient of variation (CV) [18], which is a normalized measure of dispersion of a probability distribution. The CV of concentration is considered a good measure of mixing quality. A positive value (approximately 1.0) indicates no mixing, and a value of 0 indicates complete mixing. As mixing progressed, the CV decayed exponentially from 1 to 0. We compared the mixing performance of the channels with and without grooves at various flow rates. At a flow rate of 100 μL/min, the channel with grooves (red line) showed better mixing performance (lower CV) than the channel without grooves (blue line in Figure 2e). The number of mixing cycles required for the transition from CV = 1 to CV = 0.1 was reduced from 4 to 2 cycles by the presence of grooves. These mixing results indicate that a transverse flow component was induced by the herringbone grooves.

Bottom Line: Phys.We found that the flow-induced voltage decreased significantly in the presence of herringbone grooves in both parallel and perpendicular alignments.These results support our previous interpretation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea. soohyun@kaist.ac.kr.

ABSTRACT
While flow-induced voltage over a graphene layer has been reported, its origin remains unclear. In our previous study, we suggested different mechanisms for different experimental configurations: phonon dragging effect for the parallel alignment and an enhanced out-of-plane phonon mode for the perpendicular alignment (Appl. Phys. Lett. 102:063116, 2011). In order to further examine the origin of flow-induced voltage, we introduced a transverse flow component by integrating staggered herringbone grooves in the microchannel. We found that the flow-induced voltage decreased significantly in the presence of herringbone grooves in both parallel and perpendicular alignments. These results support our previous interpretation.

No MeSH data available.


Related in: MedlinePlus