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Microfabricated valveless devices for thermal bioreactions based on diffusion-limited evaporation.

ABSTRACT: Microfluidic devices that reduce evaporative loss during thermal bioreactions such as PCR without microvalves have been developed by relying on the principle of diffusion-limited evaporation. Both theoretical and experimental results demonstrate that the sample evaporative loss can be reduced by more than 20 times using long narrow diffusion channels on both sides of the reaction region. In order to further suppress the evaporation, the driving force for liquid evaporation is reduced by two additional techniques: decreasing the interfacial temperature using thermal isolation and reducing the vapor concentration gradient by replenishing water vapor in the diffusion channels. Both thermal isolation and vapor replenishment techniques can limit the sample evaporative loss to approximately 1% of the reaction content.

SUBMITTER: Wang F

PROVIDER: S-EPMC2752386 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Microfabricated valveless devices for thermal bioreactions based on diffusion-limited evaporation.

Wang Fang F Yang Ming M Burns Mark A MA

Lab on a chip 20071031 1

Microfluidic devices that reduce evaporative loss during thermal bioreactions such as PCR without microvalves have been developed by relying on the principle of diffusion-limited evaporation. Both theoretical and experimental results demonstrate that the sample evaporative loss can be reduced by more than 20 times using long narrow diffusion channels on both sides of the reaction region. In order to further suppress the evaporation, the driving force for liquid evaporation is reduced by two addi ...[more]

PMID: 18094766

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Project description:Liquid-filled porous materials exist widely in nature and engineering fields, with the diffusion of substances in them playing an important role in system functions. Although surface evaporation is often inevitable in practical scenarios, the evaporation effects on diffusion behavior in liquid-filled porous materials have not been well explored yet. In this work, we performed noninvasive diffusion imaging experiments to observe the diffusion process of erioglaucine disodium salt dye in a liquid-filled nitrocellulose membrane under a wide range of relative humidities (RHs). We found that evaporation can significantly accelerate the diffusion rate and alter concentration distribution compared with the case without evaporation. We explained the accelerated diffusion phenomenon by the mechanism that evaporation would induce a weak flow in liquid-filled porous materials, which leads to convective diffusion, i.e., evaporation-induced flow and diffusion (EIFD). Based on the EIFD mechanism, we proposed a convective diffusion model to quantitatively predict the diffusion process in liquid-filled porous materials under evaporation and experimentally validated the model. Introducing the dimensionless Peclet (P e) number to measure the relative contribution of the evaporation effect to pure molecular diffusion, we demonstrated that even at a high RH of 95%, where the evaporation effect is usually assumed negligible in common sense, the evaporation-induced diffusion still overwhelms the molecular diffusion. The flow velocity induced by evaporation in liquid-filled porous materials was found to be 0.4-5 μm/s, comparable to flow in many biological and biomedical systems. The present analysis may help to explain the driving mechanism of tissue perfusion and provide quantitative analysis or inspire new control methods of flow and material exchange in numerous cutting-edge technologies, such as paper-based diagnostics, hydrogel-based flexible electronics, evaporation-induced electricity generation, and seawater purification.

Dataset Information

Microfabricated valveless devices for thermal bioreactions based on diffusion-limited evaporation.

Publications

Microfabricated valveless devices for thermal bioreactions based on diffusion-limited evaporation.

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