Supplementary Information for
Oil-Water Biphasic Parallel Flow for the Precise Patterning of Metals and Cells
Xuan Mu,1,2 Qionglin Liang,1Jun Zhou,2Kangning Ren,1Ping Hu,3Yiming Wang,1Zhi Zheng2and Guoan Luo1
1Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, 100005, Beijing, P. R. China
2Beijing Key Laboratory for Microanalytical Methods and Instrumentation, Department of Chemistry, Tsinghua University, 100084, Beijing, P.R. China
3 College of Chemical and Molecular Engineering, East China University of Science and Technology, 200237, Shanghai, P.R. China
1Materials
Silver nitrate, ammonia water, 1-octanol, ethanol and NaOH were bought from Beijing Chemical Factory (Beijing, China). Stannous chloride, hydrochloric acid, perchloric acid, glucose, crystal violet and tartaric acid from Yili Fine Chemical Co., Ltd (Beijing, China). Perfluorodecalin (PFD, 95%) and rhodamine 6G (R6G) were bought from Acros Organics (New Jersey, USA). Octadecyltrichlorosilane (ODS) was bought from Sigma-Aldrich (St. Louis, MO, USA). DAPI was purchased from Invitrogen (US). Ammonium ceric nitrate was bought from Beijing Chemical Reagents Company (Beijing, China). In all cases, chemicals were of analytical reagent grade and water purified in a Milli-Q system (Millipore, Bedford, MA, USA) was used.
2The detailed dimensions of microchannels
Figure S1. The PDMS microchannels are cut into slab by knife. The PDMS slab then is observed in phase contrast microscope. The dimensions are measured by ImageJ. Top. The dimensions of microchannels (200 ×20 µm). Bottom. The dimensions of microchannels (200 ×130 µm).
3The calculation of We, Ca and Re
Weber number (We) represents the ratio of inertia to surface forces, as is expressed as follow:
(1)
where p is the density (kg m-3), uis the average flow velocity (m s-1), L is the characteristic dimension of the flow (m) and γ is interfacial tension (Nm-1)between two immiscible fluids.
Capillary number (Ca) represents the competence of viscous stresses with interfacial stresses.1 It can be calculated by the following equation:
(2)
where η is viscosity(kgm-1s-1), u is velocity (ms -1)and γ is interfacial tension (Nm-1)between two immiscible fluids.
The Reynolds Number (Re) is calculated by the following equation:
(3)
where p is the density (kg m-3), uis the average flow velocity (m s-1), η is the effective viscosity (kgm-1s-1) and L is the characteristic dimension of the flow (m).The calculation required physical properties of water, PDF and octanol are listed in Table I.
Table S1. The physical properties of liquids
Water (20°C) / Octanol (20°C)2 / PFD(25°C)3Density (kg m-3) / 998.2 / 829 / 1917
Viscosity (kgm-1s-1) / 1.00210-3 / 7.2×10-3 / 5.1010-3
Interfacial tension with water (Nm-1) / - / 8.5×10-3 / 1.3×10-2
Flow velocity (ms -1) / 0.1 (for PFD) or 0.007 (for Octanol) / 0.003 / 0.02
4Water-octanol laminar flow
To demonstrate compatibility of geometric confinement with organic phase like octanol, we designed and fabricated the microfluidic chip with glass and glued tubings to resist organic phase and backpressure. For longer microchannels in glass chip with higher hydrodynamic resistance, we replace water vacuum pump with syringe pumps to provide much stronger driving force.
The individual bright field and fluorescent images in Fig.3 are shown below. The quantum yield of R6G in octanol is much larger than that in water.4Thus, underexposure of 0.2 s, only the fluorescence in octanol is visible.
Figure S2. Biphasic parallel flow of aqueous R6G solution and 1-octanol in a 185 mm-long glass microchannel. The bright field, fluorescence and merged images at inlet, middle and outlet of the channel are shown.
5Image processing and the calculation of normalized diffusion length (Dn)
In Fig. 5a, owing to the transverse diffusion, the boundary of Cr pattern is ambiguous. Thus, the original images were processed by ImageJ to make the etched pattern much clearer and be comparable. The lower and upper threshold values are set to make the images to be segmented to features of interest and background in black and white respectively.
In figure S2, the black arrows indicate the position where the width is adopted to calculate normalized diffusion length (Dn) as follow
(4)
where w is the width of the pattern and nrepresents the position. Each position is transformed into the length of the streams from the confluence point.
Figure S3. a) Original images (Top) and processed images (Bottom) of the pattern by laminar flow of miscible liquids; b) the pattern, generated by laminar flow of immiscible liquids, was simply inverted in color, owing to its distinct boundary.
Figure S4. The dynamic process of etching chromium using biphasic parallel flow. The etching time is increased from left to right. Blue arrow indicates the direction of flow. The red bars indicatethe width of PFD stream, which is unchanged during etching (patterning). Scale bar, 400 µm.
Figure S5. Contrast Image (Left)and Fluorescence image (right) of patterned bacteria using miscible solutions. The dash lines indicate the middle line of microchannels. The cells are stained with Calcium-AM.
Figure S6. Contrast Image of bacteria in microchannels ten hours after patterning. The live bacteria grew into a colony. The dash lines indicate the boundaries of microchannels.
References
(1)Squires, T. M.; Quake, S. R. Microfluidics: Fluid physics at the nanoliter scale. Rev. Mod. Phys. 2005,77, 977-1026.
(2)Mitani, S.; Sakai, K. Measurement of ultralow interfacial tension with a laser interface manipulation technique. Phy. Rev. E 2002,66, 031604.
(3)Song, H.; Tice, J. D.; Ismagilov, R. F. A microfluidic system for controlling reaction networks in time. Angew. Chem. Int. Edit. 2003,42, 768-772.
(4)Vogel, R.; Harvey, M.; Edwards, G.; Meredith, P.; Heckenberg, N.; Trau, M.; Rubinsztein-Dunlop, H. Dimer-to-monomer transformation of rhodamine 6G in aqueous PEO-PPO-PEO block copolymer solutions. Macromolecules 2002,35, 2063-2070.
A video shows the reliable immiscible laminar flow of aqueous R6G solution and 1-octanol in a serpentine glass channel with 185 mm length.
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