20210206 collagen

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Preparing the microfluidic chip

  • Anniken's design was cut from the PDMS.
  • We used Thomas' plasma cleaning procedure from 20210511_plasma_test.
  • Final product seemed to be very sterile.
  • Took collagen out from freezer at 10:50

Calculating volumes for aliquoting

  • concentration in vials: c= 5 mg/ml
  • Thin coating = 5 ug/cm^2
  • Area of coating: 2-5 cm^2 per network
  • Mass of collagen: m= 5*5 = 25ug
  • Volume of undiluted collagen: V = m/c = 0.025 mg/ 5 mg/ml = 0.005 ml = 5 ul, which is 1/1000 of a vial. It is completely unrealistic to handle such small volumes
  • If I divide the vial volume into 25 x 200 ul it should give a reasonable amount of aliquots for thin coating


Diluting and dispensing

  • Prepare sterile 17.5M acetic acid stock solution
  • Dilute 1:1000 with sterile, distilled H2O
  • Height of channels: 100 um = 0.01 cm
  • Concentration of collagen C [ug/ml] = 5 ug/cm^2 / 100 um = 5 ug/ cm^2 / 0.01 cm = 500 ug/ml = 0.5 mg/ml => dilute 1:10 with Acetic acid
  • ca 250 ul concentrated collagen + 2250 ul diluted acetic acid
  • filled in a 2.5 ml syringe, added 0.6 mm diam tip and Elveflow tube.

Filling in network

  • Anniken's network 100 um high was cut from PDMS
  • 1.6 mm diam holes
  • Plasma cleaned and assembled, tube connected
  • Syringe in syringe pump, difficult to know which rate to use
    • 1 ml/min - 0.1 ml/min gave too high pressure and tip flew off syringe
    • 0.01 ml/min - 0.2 ml/min OK (after tube was lifted a bit off the bottom in the PDMS)
    • because several disconnections (too high pressure) the tube was filled with air bubbles. These air bubbles were impossible to remove, probably due to collagen at the air-liquid interface

Suggested new procedure: fill network with pure water first and when there are no air bubbles, fill with collagen solution.

Filling with cells