Electrophoresis and Magnetohydrodyanamics: Lab on a Chip

1. Electrophoresis and • Magnetohydrodyanamics: • Lab on a Chip Streaming Potential!!!! Micro-electromechanical systems goal- “Lab on a chip” integrated sensors and measurements Based on variety of phenomena that operate at the macro scale And can be applied at the microscale, but where the application Results in altered mathematical descriptors because of the small Spatial arrangement. • Here we will look at only Two aspects of microfluidics: • Electrokinetically driven liquid micro flow • Magnetically altered electrochemical microflows

2. Flux is moles/Area-time It is equal to some constant x conc. X gradient Flux due to migration The whole volume is not pore space The distance is tortuous

3. Anode Yo Jm Charged Surface Vapp + + + + + + + + + + Jo Jm X=0 Cathode Ions migrating pull with them their water

4. Movement of ions: electroosmotic velocity of solution f is a function Based on shape Electroosmotic mobility

5. Electrosmostic Flux (carried by solution moving due to ions) where Flux due to migration

6. Data is for soils

7. 0.1 m apply 10 V Assume f = 2/3

8. Calculation of electro- Osmotic flow in a soil with 10 V applied 0.1 m apart: Typical values Potential At the shear Plane of A soil colloid

9. Solution will move through soil (in presence of 100 V/m) at A rate of 6 cm/day.

10. Electrode Reactions to carry the current Cathode Anode ++ - H+ OH- Pb2+ Precipitation reaction

12. Electroosmotic flow used for Electrospray ionization Mass Spec + Electron transfer reactions may Occur if the Electrode potentials Are large: this can create positive ions which move into the mass spec

14. Since the system is an electrochemical One – the radicals, cations, etc. produced Can be attacked and/or stabilized by the solution (remember the Gutman donor/acceptor values?) Here the solvent CH2CN Is nucleophilic and attaches Itself to the metal complex

15. Another way to get Ions for the mass Spec is to allow Electrochemical Reactions with donors And or acceptors TMPD can be used as A donor for PAH, while Dicyanodichloroquinone DDQ is used as an acceptor Nice exam question, Why?

16. Capillary Electrophoresis Flow is a “plug” which does not have the capillary drag At the edges so it gives much cleaner (less peak broadened) Separations. Pressure As driving force Electro- Osmotic flow

17. To get movement of a neutral analyte incorporate into A micelle; modulate the charge on the micelle using pH

18. Where f is the shape function

19. Lab on a Chip Electrophoresis

20. J. Wang, M. Pumera / Talanta 69 (2006) 984–987 Fig. 1. Microchip system for FIA with electrochemical detection: (a) run buffer reservoir, (b) sample reservoir, (c) unused/second sample reservoir, (d) detection reservoir, (e) platinum cathode for FIA, (f) Ag/AgCl wire reference electrode, (g) platinum counter electrode and (h) detection electrode.

22. Goal use electrochemical detectin For a miniature electrochemical separating Device, requires decoupling of the Detection current from the separation systme Hold At ground for separation Vickers, Electrophoresis, 2005

25. Lab on a Chip Stripping Analysis

28. Small volume Large volume Emily A. Clark and Ingrid Fritsch, Factors influencing redox Magnetohydrodynamic-induced convection for enhancement of stripping analysis Anal. Chem. 2006, 78, 3745-3751

29. Small volume Smaller enhancements in the small volume system using a permanent magnet Emily A. Clark and Ingrid Fritsch, Factors influencing redox Magnetohydrodynamic-induced convection for enhancement of stripping analysis Anal. Chem. 2006, 78, 3745-3751

30. Use of magnetic fields to drive enhanced flux Deposit large number of ions into mercury NOT of interest to generate A large flux, J, to the surface. If done in the presence of a magnetic field (B) Then you get a lorentz force (N/m^3) on the charge carrying ions which Operates by the right handed rule to generate a magneto hydrodynamic Convection toforce soluton to the surface. Emily A. Clark and Ingrid Fritsch, Anodic Stripping Voltammetric Enhancement by Redox Magnetohydrodynamics Anal. Chem. 2004, 76, 2415-2418

31. Magnetic field generated by a small electromagnet Emily A. Clark and Ingrid Fritsch, Anodic Stripping Voltammetric Enhancement by Redox Magnetohydrodynamics Anal. Chem. 2004, 76, 2415-2418

32. Fritsch JES 2006

33. B Fritsch JES 2006

34. Magnetic field pushes fluid down Magnetic field pushes fluid up Fritsch JES 2006

35. Removes much of the diffusional Shape to the voltammogram Which will allow for more Robust measurement of Concentration and/or kinetics Flow rate in the microchannel Fritsch JES 2006

36. Fritsch JES 2006

37. Figure 2. Absorbance versus time curves for a plug (concentration, 7.7 mg/mL) of Fe2O3 nanoparticles injected into the lower flow stream at a flow rate of 15 íL/min. Monitoring the upper channel with (red - - -) and without (red s), and bottom channel with (blue - - -) and without (blue s), the applied magnetic field. Asterisk indicates the point where the magnetic field was removed. Inset: Au nanoparticles eluting from the lower channel with (blue - - -) and without (blue s) a magnetic field under equivalent conditions. Anal. Chem. 2007 79 5746-5752 Magnetic Field Switching of Nanoparticles between Orthogonal Microfluidic Channels Andrew H. Latham, Anand N. Tarpara, and Mary Elizabeth Williams*

38. Anal. Chem. 2007 79 5746-5752 Magnetic Field Switching of Nanoparticles between Orthogonal Microfluidic Channels Andrew H. Latham, Anand N. Tarpara, and Mary Elizabeth Williams* Using the ability to move magnetic particles, we envision microfludic devices in which external magnetic fields, generated by electromagnets or permanent magnets, can be used to perform separations, injections, and manipulations in microfluidic channels. Given the already widespread use of magnetic beads in biological assays, development of compatible analytical and microscale approaches would be of great use. These initial experiments show that standard operations for microfluidic devices such as injection/ removal, mixing, separation, concentration, and fluid/particle handling are all possible with correctly functionalized magnetic particles and the appropriate field strength and flow rates. Figure 7. Absorbance versus time for both the upper and lower channels while pulsating the magnetic field (10 s on/20 s off) with a continuous stream of Fe2O3 nanoparticles flowing through the upper channel at a flow rate of 15 íL/min.

39. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems Two kinds of magnetic force Moving charges Magnetic dipoles Electromagnetic force on moving Charge is related to q the charge And the velocity of the particle, The intensity of the electric field and The magnetic induction, B Anions and cations experience same direction Of force: Moving ions transfer momentum to the solvent Causing it to behave as if it were subject to the force

40. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems For dipoles the average magnetic moment per dipole

41. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems

42. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems

43. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems current

44. Leventis Anal. Chem. 2001 Magnetohydrodynamic Electrochemistry in the Field of Nd-Fe-B Magnets. Theory, Experiment, and Application in Self-Powered Flow Delivery Systems

45. JACS 2005