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Project Update June 22, 2006

Project Update June 22, 2006. ME342A. Project Goal. Design a bioMEMs substrate to apply and measure electromechanical forces in the differentiation of human embryonic stem cell-derived (hESC)-cardiac myocytes (CM). hESC-CMs organized in embryoid body. Contractility Electrophysiology

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Project Update June 22, 2006

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  1. Project UpdateJune 22, 2006 ME342A

  2. Project Goal • Design a bioMEMs substrate to apply and measure electromechanical forces in the differentiation of human embryonic stem cell-derived (hESC)-cardiac myocytes (CM) hESC-CMs organized in embryoid body Contractility Electrophysiology Mechanical force Undifferentiated hESCs-Fluc-eGFP (DAPI nuclear stain) bioMEMS device

  3. BioMEMS: Engineering Specs

  4. BioMEMS: Device Design Poly(dimethylsiloxane) (PDMS): A biocompatible elastomeric polymer with low water permeability Quartz: Optically transparent substrate Gold: Biocompatible thin film electrodes Indium-Tin Oxide (ITO): Transparent thin film conducting electrodes traces B. Strained state A. Unstrained state

  5. BioMEMS: Loading Curves • Young’s Modulus PDMS E = 500kPa • Thickness = 50um • Membrane length = 1cm • Loading post length = 0.7cm

  6. BioMEMS: Fabrication 1. Double polished quartz wafer ~ 500μm Quartz

  7. BioMEMS: Fabrication 2. Laser cut alignment marks & pressure channels (frontside wafer) Channels etched to apply suction pressure to PDMS substrate Quartz

  8. BioMEMS: Fabrication 3. Laser cut channels to connect to pressure lines (backside wafer) Channels backside to connect to vacuum source Quartz

  9. Alternative Step—Replace 3 & 4 3a. Laser cut channels to connect to pressure lines (backside wafer) Channels frontside etch to connect to vacuum source *will require punch holes in PDMS layer, so need alignment marks on PDMS layer for this interface…same as uFluidic interconnect Quartz

  10. BioMEMS: Fabrication 4. Bond a second quartz wafer to the first quartz wafer Channels backside to connect to vacuum source Quartz

  11. BioMEMS: Fabrication 5. Fill with sacrificial layer—acrylate or agaraose. Squeeqy off. Channels backside to connect to vacuum source Quartz Sacrificial later

  12. BioMEMS: Fabrication 6. Spin photoresist and expose area for second sacrificial layer (loading posts and vacuum channel are covered). Channels backside to connect to vacuum source Quartz Sacrificial later Photoresist

  13. BioMEMS: Fabrication 7. Cast second sacrificial layer of acrylate Channels backside to connect to vacuum source Quartz Sacrificial later Photoresist

  14. BioMEMS: Fabrication 8. Strip photoresist (should remove sacrificial layer from alignment marks here) and plasma surface area for PDMS Channels backside to connect to vacuum source Quartz Sacrificial later Photoresist

  15. BioMEMS: Fabrication 9. Spin PDMS Quartz Sacrificial later Photoresist PDMS

  16. BioMEMS: Fabrication 10. Spin photoresist Quartz Sacrificial later Photoresist PDMS

  17. BioMEMS: Fabrication 10. Ebeam 20nm Ti (adhesion layer for gold and traces for electrodes) PDMS Titanium Quartz Sacrificial layer Photoresist

  18. BioMEMS: Fabrication 11. Ebeam 150nm gold film (actual stretchable traces—geometry) PDMS Titanium Gold Quartz Sacrificial layer Photoresist

  19. BioMEMS: Fabrication 12. Strip and pattern photo resist for PDMS Titanium Gold Quartz Sacrificial layer Photoresist

  20. BioMEMS: Fabrication 13. Strip and pattern photo resist for electrodes, gauges, contact pads PDMS Titanium Gold Quartz Sacrificial layer Photoresist

  21. BioMEMS: Fabrication 14. Ebeam gold electrodes PDMS Titanium Gold Quartz Sacrificial layer Photoresist

  22. BioMEMS: Fabrication 15. Strip photoresist and passivate PDMS Titanium Gold Quartz Sacrificial layer Photoresist Passivation layer

  23. BioMEMS: Fabrication 16. Dissolve sacrificial layer PDMS Titanium Gold Quartz Sacrificial layer Photoresist Passivation layer

  24. BioMEMS: Stretchable Electrodes C. S. Park, M. Maghribi Characterizing the Material Properties of Polymer-Based Microelectrode Arrays for Retinal Prosthesis

  25. Stimulation Electrodes • Goal: To pattern gold electrodes within a flow chamber for selectively stimulating hESCs • Electrodes 100μm x 5000μm (10 per well) • Interelectrode distance 1000μm • Contacts pads 2mm x 2mm (10 per well) • Polished glass wafers 1 mm thick

  26. BioMEMS: Strain gauge • Need a strain gauge and a reference strain gauge for every deformable area.

  27. Strain gauge design • Length (L = 1 mm) • Trace width (w = 50 um) • Distance between turns (p = 450 um) • Number of turns (t = 3—38) • Thickness of gold electrodes ~several hundred nm

  28. Mechanical Strain • Goal: To apply cyclic mechanical strain to hESC precursor cells and observe differentiation

  29. Next Steps • QFD write-up for Beth • Refine process cartoons • Define geometry of membrane and electrodes • ANSYS analysis of membrane and electrode deformation • Define redundant layers—ie, cover up alignment marks w/ foil • Creation of Ledit mask • Selection of machines • Training

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