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Abstract
Convective Marangoni flow pumps can drive liquid streams in microfluidic devices, and allow static channel layouts to be replaced by “virtual” boundaries that emerge in the liquid phase. However, while transfer from location A → location B can be modified easily via physicochemical control over the surface tension gradients involved, it remains a challenge to establish chemical transfer cascades A → B → C, which is prerequisite to more complex reconfigurable liquid systems. Here, we present a bottom-up approach for convective Marangoni flow pumps, combining the self-assembly of a linear amphiphile into myelin filaments with the emulsification of oil microdroplets and the occurrence of Marangoni backflows underneath the air/water interface. The system allows chemical transfer over multiple steps amongst droplets that are positioned at the air/water interface. Our concept provides a toolbox for the design of controllable surface tension gradients and triggered microemulsion release in reconfigurable all-in-liquid microfluidics.
Supplementary materials
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Supplementary Information
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Supplementary Figures
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Title
Supplementary Movie 1 – corresponding to Figure 2b,d
Description
Optical and fluorescence (λex = 635 nm) recordings of a 1.0 μL source droplet and a 2.0 μL drain droplet (10 mg mL–1 Nile Blue A in linalool) deposited at an aqueous medium. The droplets are positioned at steel pillars. The optical and fluorescence recordings are of two different experiments.
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Supplementary Movie 2 – corresponding to Supplementary Figure 3
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Left movie: Optical microscopy recordings of a linalool drain droplet (2.0 μL) deposited at an aqueous medium with 1.0 mM C12E3 added. At t = 150 s, a 1.0 μL source droplet is also deposited. Middle movie: Optical microscopy recordings of a 80 v/v% linalool and 20 v/v% C12E3 drain droplet (2.0 μL) deposited at an aqueous medium. At t = 200 s, a 1.0 μL source droplet is also deposited. Right movie: Optical microscopy recordings of a 60 v/v% linalool and 40 v/v% C12E3 drain droplet (2.0 μL) deposited at an aqueous medium. At t = 200 s, a 1.0 μL source droplet is also deposited. In all three videos, the droplets are positioned at steel pillars.
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Supplementary Movie 3 – corresponding to Figure 3b,c
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Optical and fluorescence (λex = 635 nm) microscopy recordings of a 1.0 μL source droplet, a 2.0 μL linalool drain droplet with dye (bottom; 10 mg mL–1 Nile Blue A) and a 2.0 μL 60 v/v% linalool and 40 v/v% C12E3 drain droplet (upper) deposited at an aqueous medium. The droplets are positioned at steel pillars. The optical and fluorescence recordings are of two different experiments. The yellow box indicates the area observed in the fluorescence microscopy recording.
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Supplementary Movie 4 – corresponding to Figure 4d-f
Description
Optical microscopy recordings of a 1.0 μL source droplet and various combinations of drains droplets (2.0 μL) deposited at an aqueous medium. The bottom drain droplet is always the strongest and it is loaded with a dye (10 mg mL–1 Nile Blue A). The upper drain droplet is the weakest and contains no dye. The droplets are positioned at steel pillars. The colormap indicates the strength difference between the two drains (ΔΔγ).
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Supplementary Movie 5 – corresponding to Figure 4d
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Fluorescence microscopy recordings (λex = 635 nm) of a 1.0 μL source droplet and various combinations of drains droplets (2.0 μL) deposited at an aqueous medium. The bottom drain droplet is always the strongest and it is loaded with a dye (10 mg mL–1 Nile Blue A). The upper drain droplet is the weakest and contains no dye. The droplets are positioned at steel pillars. The colormap indicates the strength difference between the two drains (ΔΔγ). The blue box indicates the area observed in the fluorescence microscopy recordings.
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Supplementary Movie 6 – corresponding to Figure 5b
Description
Optical and fluorescence (λex = 385 nm) microscopy recordings of a 1.0 μL source droplet, a 2.0 μL linalool drain droplet with heptylamine (bottom; 5 v/v%) and a 2.0 μL 60 v/v% linalool and 40 v/v% C12E3 drain droplet loaded with CPM (upper; 90 μg mL–1) deposited at an aqueous medium. The droplets are positioned at steel pillars. The optical and fluorescence recordings are of the same experiment. The yellow box indicates the area observed in both the optical and fluorescence microscopy recordings.
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Supplementary Movie 7 – corresponding to Figure 5e
Description
Optical and two fluorescence (middle: λex = 385 nm: right: λex = 635 nm) microscopy recordings of two 1.0 μL source droplets, a 2.0 μL linalool drain droplet loaded with dye (upper left; 10 mg mL–1 Nile Blue A), a 2.0 μL 60 v/v% linalool and 40 v/v% C12E3 drain droplet loaded with CPM (middle; 90 μg mL–1) and a 2.0 μL linalool drain droplet with heptylamine (upper right; 5 v/v%) deposited at an aqueous medium. The droplets are positioned at steel pillars. Two replicate experiments are shown (upper three recordings and bottom three recordings). The yellow box indicates the area observed in both the optical and fluorescence microscopy recordings.
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Supplementary Movie 8 – corresponding to Figure 6c,d
Description
Left: Optical microscopy recordings of a 1.0 μL source droplet, a 2.0 μL linalool drain droplet with dye (left bottom; 10 mg mL–1 Nile Blue A), a 2.0 μL photoactivatable drain (left middle; 2 wt% sodium oleate, 12 w/v% 2-nitrobenzaldehyde in 1:2 oleic acid:linalool mixture) and a 2.0 μL 50 v/v% linalool and 50 v/v% C12E3 drain droplet (upper) deposited at an aqueous medium. Right: Optical microscopy recordings of a 1 μL source droplet, a 2 μL linalool drain droplet with dye (left bottom; 10 mg/mL Nile Blue A), a 2 μL photoactivatable drain (right upper: 2 wt% sodium oleate, 12 w/v% 2-nitrobenzaldehyde in 1:2 oleic acid:linalool mixture) and a 2μL 50v/v% linalool and 50 v/v% C12E3 drain droplet (middle upper) deposited at an aqueous medium. In both recordings, the droplets are positioned at steel pillars. The appearance of the purple square indicates when the system is exposed to UV.
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