High response speed microfluidic ice valves with enhanced thermal conductivity and a movable refrigeration source

Chaorun Si,Weichao Wu,Xiaobao Cao,Songtao Hu

doi:10.1038/srep40570

Chaorun Si, Weichao Wu + Show 2 more

Open Access

https://doi.org/10.1038/srep40570

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Abstract

Due to their ease of fabrication, facile use and low cost, ice valves have great potential for use in microfluidic platforms. For this to be possible, a rapid response speed is key and hence there is still much scope for improvement in current ice valve technology. Therefore, in this study, an ice valve with enhanced thermal conductivity and a movable refrigeration source has been developed. An embedded aluminium cylinder is used to dramatically enhance the heat conduction performance of the microfluidic platform and a movable thermoelectric unit eliminates the thermal inertia, resulting in a faster cooling process. The proposed ice valve achieves very short closing times (0.37 s at 10 μL/min) and also operates at high flow rates (1150 μL/min). Furthermore, the response time of the valve decreased by a factor of 8 when compared to current state of the art technology.

Highlights

The platform consists of a PMMA (poly(methyl methacrylate)) microfluidic device embedded with an aluminium cylinder covered with a layer of anti-freeze solution, a movable TE unit and a water cooling system www.nature.com/scientificreports/
The closing time increases with the flow rate and is less than a second when the flow rate is below 500 μL/min
Compared with ice valves reported in previous studies[11,13,14], the closing time of this ice valve is over 8 times shorter at the same flow rates

Summary

Experimental Section

The platform consists of a PMMA (poly(methyl methacrylate)) microfluidic device embedded with an aluminium cylinder covered with a layer of anti-freeze solution, a movable TE unit and a water cooling system. Without the anti-freeze solution, the TE unit will condense moisture from the air to form an ice layer on the top of the cooling head, which will reduce the heat transfer. The closing time of the ice valve is defined from the point when the device contacts with the TE unit to the point that the valve closes (the flow stops) These experiments were conducted at room temperature (19.6 °C) and the cooling head was cooled to −45.2 °C (as measured using a k-type thermocouple) prior to contact with the device. When no more air bubbles were visible in the tubing, the valve was deemed closed

Results and Discussion

Conclusions

Additional Information