Design _ Fabrication_ Microfluidic Multi-Patch

							Microfluidic Multi-Patch Recording
              Unit
           Kachi Odoemene
      Physiological Sensing Facility
           Purdue University
           Patch Clamp Technique
• Measure intracellular                           Closed
  current from single ion                         Open
  channels of excitable
  cells
                             Glass electrode
• Glass micropipette 1-
  2um in diameter                 Ion channel
• Giga-ohm seal
                                  Cell Membrane
  formation between
  glass electrode and cell
  membrane

 Hamil, O et al 1981
 Neher and Sakman 1992
     Limitations of Traditional Patch
                                                     • Operation requires high
                                                       skill level
                                                     • Low throughput
                                                        – Approximately 10
                                                          cells/day
                                                     • Impossible to record
                                                       from population of
                                                       neurons in local
                                                       network
http://www.farma.ku.dk/uploads/pics/PatchClamp.jpg
                       Conceptual Design
                                            Backside
                                            microfluidic
 Circular Patch Site                        channels




Access port
for electrode
and suction                                PDMS
tubing                                     chamber
           Patch Substrate Design
                     Top side       Back side




     Patch pores
   1-2 um diameter


• Double sided processing on either glass or silicon
  substrate
   – Backside: Tapered microfluidic channels
        • From 10 um wide to 500 um wide
   – Topside: Patch pores and microtubing access port
        • Holes aligned to mate with with channel
• Application dependent array size and spacing
 Proof of Device Concept in Silicon
• Implement chip design
  using Deep Reactive Ion
  Etching (DRIE)
   – Fast etch rate (>8
     um/min)
                            SEM micrographs of microchannels
• Wet oxidation to create
  glass-like layer and
  shrink patch pores
• Integration with PDMS

                            Confocal micrograph of narrow channels
                Glass Fabrication
• High aspect ratio glass
  DRIE requires hard
  mask
   – Thick electroplated
     nickel (>5 um)         Nickel hard mask patterned with photoresist

• Very slow etch rate
   – 0.5 um/min
• Currently laser
  micromachining
  channels and pores
                            Channels etched via DRIE, with NI hard mask
 Potential Commercial Advantages
• Overall unique chip design in glass
• Embedded microfluidic channels
   – Isolated studies of channels of single cell or cells in a
     network
• Glass substrate allowing giga-seal formation &
  electrical isolation
• Recordings from adherent cells in tissue culture
  and cells with native ion channels
• Device automation will lead to high throughput
  drug screening applications