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Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting.

Hsu TH, Manakasettharn S, Taylor JA, Krupenkin T - Sci Rep (2015)

Bottom Line: We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics.Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone.This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Wisconsin-Madison, 1513 UniversityAvenue, Mechanical Engineering Building Room 2238, Madison, WI, 53706, USA.

ABSTRACT
We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10(-6) W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.

No MeSH data available.


Related in: MedlinePlus

Theoretical and experimental investigation of the bubble dynamics.(a–d) CFD simulation of the bubble growth and collapse process. Red color indicates the volume occupied by the air, and blue color represents the volume occupied by the mercury. (e) The results of the CFD modeling for the area occupied by air. For this simulation the gauge pressures at the air inlet (PAir - PHg) and at the mercury (PHg) were 0.08 bar and 0.08 bar, respectively. The predicted oscillation period was about 1.4 ms. (f) Experimental results for the relative light intensity vs. time. The obtained oscillation period is about 1.7 ms.
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f4: Theoretical and experimental investigation of the bubble dynamics.(a–d) CFD simulation of the bubble growth and collapse process. Red color indicates the volume occupied by the air, and blue color represents the volume occupied by the mercury. (e) The results of the CFD modeling for the area occupied by air. For this simulation the gauge pressures at the air inlet (PAir - PHg) and at the mercury (PHg) were 0.08 bar and 0.08 bar, respectively. The predicted oscillation period was about 1.4 ms. (f) Experimental results for the relative light intensity vs. time. The obtained oscillation period is about 1.7 ms.

Mentions: The bubbler approach is predicated on the ability to achieve a stable and predictable bubble self-oscillation process. Thus we paid special attention to theoretical and experimental investigation of the bubble growth and collapse dynamics. To this end we combined experimental studies of the bubble behavior with the computational fluid dynamics (CFD) modeling of the bubble growth and collapse process. The laminar two phase flow CFD model was used to obtain the numerical solution for the fluid velocity distribution and the bubble interface dynamics. The dielectric fluid and the conductive liquid used in most of the simulations were air and mercury respectively. Our previous experiments2 demonstrated that the REWOD process works best when room-temperature liquid metals are used as a conductive liquid. In particular, mercury and a gallium-indium alloy called Galinstan were shown to be well suited for use with REWOD2. In this work we utilized mercury due to its chemical stability and resistance to oxidation. In potential commercial applications mercury is undesirable due to its toxicity and the use of gallium-indium alloys might be preferred. The applied gauge pressures at the air inlet (i.e. the hole through the electrode) and at the mercury-filled gap between the electrode and the membrane were kept constant during the oscillation process. The simulation domain (electrode diameter) was varied between 1,000 μm and 1,200 μm. The diameter of the air inlet was varied between 140 μm and 200 μm. The gap between the electrode and the membrane was varied between 100 μm and 130 μm. The details of the CFD modeling procedure are available in the Supplementary Materials. The four major steps of the bubble oscillation process, which were observed in the model, are shown in Fig. 4(a–d) (also see Supplementary Video 2). At the beginning of the oscillation cycle the compressed air supplied through the inlet initiates the bubble growth (see Fig. 4(a)), which continues until the bubble touches the membrane, breaking the remaining mercury film and causing it to rapidly retract towards the edge of the electrode, as shown in Fig. 4(b,c). At this point the bubble takes the pancake shape and starts collapsing towards the center of the electrode, rapidly completing the self-oscillation cycle, as shown in Fig. 4(d).


Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting.

Hsu TH, Manakasettharn S, Taylor JA, Krupenkin T - Sci Rep (2015)

Theoretical and experimental investigation of the bubble dynamics.(a–d) CFD simulation of the bubble growth and collapse process. Red color indicates the volume occupied by the air, and blue color represents the volume occupied by the mercury. (e) The results of the CFD modeling for the area occupied by air. For this simulation the gauge pressures at the air inlet (PAir - PHg) and at the mercury (PHg) were 0.08 bar and 0.08 bar, respectively. The predicted oscillation period was about 1.4 ms. (f) Experimental results for the relative light intensity vs. time. The obtained oscillation period is about 1.7 ms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645099&req=5

f4: Theoretical and experimental investigation of the bubble dynamics.(a–d) CFD simulation of the bubble growth and collapse process. Red color indicates the volume occupied by the air, and blue color represents the volume occupied by the mercury. (e) The results of the CFD modeling for the area occupied by air. For this simulation the gauge pressures at the air inlet (PAir - PHg) and at the mercury (PHg) were 0.08 bar and 0.08 bar, respectively. The predicted oscillation period was about 1.4 ms. (f) Experimental results for the relative light intensity vs. time. The obtained oscillation period is about 1.7 ms.
Mentions: The bubbler approach is predicated on the ability to achieve a stable and predictable bubble self-oscillation process. Thus we paid special attention to theoretical and experimental investigation of the bubble growth and collapse dynamics. To this end we combined experimental studies of the bubble behavior with the computational fluid dynamics (CFD) modeling of the bubble growth and collapse process. The laminar two phase flow CFD model was used to obtain the numerical solution for the fluid velocity distribution and the bubble interface dynamics. The dielectric fluid and the conductive liquid used in most of the simulations were air and mercury respectively. Our previous experiments2 demonstrated that the REWOD process works best when room-temperature liquid metals are used as a conductive liquid. In particular, mercury and a gallium-indium alloy called Galinstan were shown to be well suited for use with REWOD2. In this work we utilized mercury due to its chemical stability and resistance to oxidation. In potential commercial applications mercury is undesirable due to its toxicity and the use of gallium-indium alloys might be preferred. The applied gauge pressures at the air inlet (i.e. the hole through the electrode) and at the mercury-filled gap between the electrode and the membrane were kept constant during the oscillation process. The simulation domain (electrode diameter) was varied between 1,000 μm and 1,200 μm. The diameter of the air inlet was varied between 140 μm and 200 μm. The gap between the electrode and the membrane was varied between 100 μm and 130 μm. The details of the CFD modeling procedure are available in the Supplementary Materials. The four major steps of the bubble oscillation process, which were observed in the model, are shown in Fig. 4(a–d) (also see Supplementary Video 2). At the beginning of the oscillation cycle the compressed air supplied through the inlet initiates the bubble growth (see Fig. 4(a)), which continues until the bubble touches the membrane, breaking the remaining mercury film and causing it to rapidly retract towards the edge of the electrode, as shown in Fig. 4(b,c). At this point the bubble takes the pancake shape and starts collapsing towards the center of the electrode, rapidly completing the self-oscillation cycle, as shown in Fig. 4(d).

Bottom Line: We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics.Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone.This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Wisconsin-Madison, 1513 UniversityAvenue, Mechanical Engineering Building Room 2238, Madison, WI, 53706, USA.

ABSTRACT
We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10(-6) W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.

No MeSH data available.


Related in: MedlinePlus