Research

Since 2004, Fan-Tasy Lab has been developing an “electromicrofluidic (EMF) platform” employing two important electrokinetic forces, electrowetting-on-dielectric (EWOD) and dielectrophoresis (DEP), to actuate microfluids sandwiched between parallel glass plates containing proper electrodes. For the simple sandwich structure (substrate / fluids / substrate) without sophisticated microchannels, the EMF platform is easily fabricated, packaged, and operated.

On the EMF platform, EWOD efficiently varies the contact angle of aqueous droplets and has been widely studied in droplet actuations for lab-on-a-chip (LOC), point-of-care (POC) in vitro diagnosis (IVD) devices, liquid lenses, and displays [1]. Alternatively, DEP drives polarizable particles and liquids by non-uniform electric fields. By skillful integration of EWOD and DEP, our team has demonstrated various microfluidic functions, showing that EMF is general to manipulate objects (1) with distinct conductivities (water and oil droplets), (2) on cross-scales (mm droplets and μm particles/cells), (3) in multiphases (solid, liquid, gas, and plasma), and (4) in adjustable geometries (discrete droplets and continuous virtual microchannels):

General to fluid conductivity

  • Driving conductive (e.g., water) droplets by EWOD and dielectric (e.g.,  oil, Fig. 1(a) [2]) by DEP.
  • Forming water-core/oil-shell encapsulated droplets with a metered and removable oil shell  [3] for artificial cell membrane (bilayer lipid membrane) formation [4], protein crystallization under programmable evaporation rate by tuning shell thickness (Fig. 1(b)) and droplet-based liquid-liquid extraction.
  • Manipulating crosslinkable prepolymer droplets with a wide rage of conductivities to obtain hydrogels with novel physical, chemical, and biological properties (Fig. 1(c)) [5].

Fig2

Fig. 1 Manipulation of fluids with distinct conductivities.

General to object scales

  • Concentrating mammalian cells by DEP in EWOD-driven droplets (Fig. 2(a) [6]).
  • Focusing bio-functionalized particles for enhancing the fluorescent signal of the immunoassay (Fig. 2(b) [7, 8]).
  • Forming particle chains to alter the optical transmittance for displays (Fig. 2(c) [9]).

Fig3

Fig. 2 Actuations of liquids and particles on cross-scales.

General to all phases

  • Liquid phase (Fig. 1).
  • Gas  and plasma  phases: gas bubbles (Fig. 3(a) [10]) and plasma in bubbles (Fig. 3(b) [10]).
  • Solid phase: crosslinked solid blocks (Fig. 3(c) [5]) containing reorganized particles.

Fig4

Fig. 3 Manipulating objects in multiphases.

 General to liquid geometry

  • Achieving virtual microchannels of fluids with higher permittivity (e.g., water) deformed and driven in another immiscible fluid with lower permittivity (e.g., air or oil) by DEP (Fig. 4(a) [11] and 4(b)).
  • Liquid-core/liquid-cladding optical waveguides [12].
  • EMF-based lithography with curable liquids.
  • Continuous pumping along the virtual microchannels between droplets by electrically adjusting the pressure difference between two droplets connected by a virtual microchannel.

Fig5

Fig. 4 Driving liquids in various formats: discrete droplets and continuous channels.

With the generic features of the EMF platform described above, we demonstrated the construction of 3D heterogeneous architectures on the EMF platform [5] to provide new tools for sophisticated 3D heterogeneous in-vivo-like architectures.

Fig1

Fig. 5 3D heterogeneous in-vivo-like architectures constructed on the EMF platform.

Mass production of EMF platform

Our team also collaborate with Taiwan and international companies to develop the mass production processes for the EMF platform. The examples include:

  • Heterogeneous packaging of silicon-based sensors to EMF cartridges (Fig. 6(a) and 6(b)).
  • Standard foundry for EMF platform with better performance (Fig. 6(c)).

Fig6

Fig. 6 Commercialization of EMF platform with industry collaborators.

References

  1. S.-K. Fan and F.-M. Wang, “Multiphase Optofluidics on an Electro-Microfluidic Platform Powered by Electrowetting and Dielectrophoresis,” Lab on a Chip, 14, 2014, 2728-2738.
  2. S.-K. Fan, T.-H. Hsieh, and D.-Y. Lin, “General digital microfluidic platform manipulating dielectric and conductive droplets by dielectrophoresis and electrowetting,” Lab on a Chip, 9, 2009, 1236-1242.
  3. S.-K. Fan, Y.-W. Hsu, and C.-H. Chen, “Encapsulated droplets with metered and removable oil shells by electrowetting and dielectrophoresis,” Lab on a Chip, 11, 2011, 2500-2508.
  4. S.-K. Fan, C.-W. Chen, Y.-Y. Lin, L.-C. Chen, F.-G. Tseng, and R.-L. Pan, “Formation of Suspended Bilayer Lipid Membrane between Electrowetting-Driven Encapsulated Droplets,” Biomicrofluidics, 8, 2014, 052006.
  5. M.-Y. Chiang, Y.-W. Hsu, H.-Y. Hsieh, S.-Y. Chen, S.-K. Fan, “Constructing 3D heterogeneous hydrogels from electrically manipulated prepolymer droplets and crosslinked microgels,” Science Advances, 2, 2016, e1600964.
  6. S.-K. Fan, P.-W. Huang, T.-T. Wang, and Y.-H. Peng, “Cross-scale electric manipulations of cells and droplets by frequency-modulated dielectrophoresis and electrowetting,” Lab on a Chip, 8, 2008, 1325-1331.
  7. C.-Y. Huang, P.-H. Shih, P.-Y. Tsai, I-C. Lee, H.-Y. Hsu, H.-Y. Huang, S.-K. Fan, and W. Hsu, “AMPFLUID: aggregation magnified post-assay fluorescence for ultrasensitive immunodetection on digital microfluidics,” Proceedings of the IEEE, 103, 2015, 225-235.
  8. C.-Y. Huang, P.-Y. Tsai, I-C. Lee, H.-Y. Hsu, H.-Y. Huang, S.-K. Fan, D.-J. Yao, C.-H. Liu, and W. Hsu, “A highly efficient bead extraction technique with low bead number for digital microfluidic immunoassay,” Biomicrofluidics, 10, 2016, 011901.
  9. S.-K. Fan, C.-P. Chiu, C.-H. Hsu, S.-C. Chen, L.-L. Huang, Y.-H. Lin, W.-F. Fang, J.-K. Chen, and J.-T. Yang, “Particle Chain Display – an Optofluidic Electronic Paper,” Lab on a Chip, 12, 2012, 4870-4876.
  10. S.-K. Fan, Y.-T. Shen , L.-P. Tsai, C.-C. Hsu, F.-H. Ko and Y.-T. Cheng, “Atmospheric-Pressure Microplasma in Dielectrophoresis-Driven Bubbles for Optical Emission Spectroscopy,” Lab on a Chip, 12, 2012, 3694-3699.
  11. S.-K. Fan, W.-J. Chen, T.-H. Lin, T.-T. Wang, and Y.-C. Lin, “Reconfigurable liquid pumping in electric-field-defined virtual microchannels by dielectrophoresis,” Lab on a Chip, 9, 2009, 1590-1595.
  12. S.-K. Fan, H.-P. Lee, C.-C. Chien, Y.-W. Lu, Y. Chiu, and F.-Y. Lin, “Reconfigurable liquid-core/liquid-cladding optical waveguides with dielectrophoresis-driven virtual microchannels on an electromicrofluidic platform,” Lab on a Chip, 16, 2016, 847-854.

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