Tousimis Automegasamdri 915B – Critical Point Dryer

Important to know:

  • Ethanol should be ordered by email or phone to CMi facilities staff (Jean-Marie Voirol or Patrick Madliger) at least half a day before using CPD.

I. Supercritical point dryer

This installation is dedicated for drying freshly released structures with minimum sticking issues (samples are dried at CO2 supercritical point).

At the very beginning the CO2 is in its liquid phase, and at low temperature (10°C).
During the HEAT mode, the pressure and the temperature are increased (A -> B -> C) in order to reach the critical phase.
During the BLEED and VENT mode the pressure and the temperature are decreased to reach the gaseous phase (C – > D -> E) without directly crossing the transition liquid to gaz that is responsible for stiction of critical suspended structures.

II. Modus operandi

  • Log ON the tool on Zone14 computer and check in grey room at back of the tool that the CO2 bottle is open.
  • Turn the chiller ON for at least 30 minutes prior to process run.
  • Turn the condenser on.
  • Turn the chamber on. Green led on VENT button will illuminate. This indicates the power is on and the unit is in standing by in the VENT mode.

Wait for 3 to 5 minutes. The pressure gauge should be in the “0 psi” range. Remove the chamber lid and carefully place chamber lid on a soft surface (clean room tissue) face down. Once the chamber lid is removed, always protect the face in contact with the chamber.

  • Press the VENT button once. The VENT led will begin to blink indicating the 915B is in STANDBY mode.
  • Introduce ultra-pure alcohol into the chamber. Fill the chamber with sufficient alcohol to cover the samples. NEVER EXPOSE CHAMBER TO ANY ACIDS.
  • Carefully transfer the samples into the system process chamber. For best results, minimize exposure time to air.
  • Carefully lower the chamber lid onto chamber. Initially use fingers to evenly tighten the 8 knurled nuts around the circumference of the chamber lid. Use the spanning wrench provided to uniformly tighten each knurl nut in a “star pattern”. Tighten the knurl nuts in the numbered sequence. Repeat this rotation “star pattern” sequence until the knurl nuts are unable to tighten further.
  • Once the chamber lid is secured, set the PURGE timer located to the right of the push button switches:

To purge 1/4 chamber full of alcohol = 10 minute purge time.
To purge 1/2 chamber full of alcohol = 15 minute purge time.

  • Press the COOL button. The COOL led light will go on, and the VENT led will turn off. The chamber temperature will slowly begin to drop : the process chamber will cool from room temperature to 10°C in approximately 3 minutes. Once the chamber temperature reaches 10°C, follow the next steps.
  • Press the FILL button. During the FILL mode, liquid CO2 enters and fill the chamber for 8 minutes. From this steps, the system will automatically cycle through all the drying sequence modes until process completion.
  • After the 8 minute FILL mode expires, the system will automatically advance into the PURGE mode. This will be indicated by the illumination of the PURGE led. The system will now remain in the PURGE mode for the duration of time pre-set by the operator via the PURGE timer.
  • Upon completion of the PURGE mode, the system automatically advance into a POST-PURGE-FILL mode in which the chamber fills with liquid CO2 for an additional 4 minutes. This mode is indicated by both the FILL and PURGE leds simultaneous illumination.
  • Upon completion of the POST-PURGE-FILL mode, the PURGE and FILL leds will turn off and the HEAT led will illuminate and the HEAT mode starts. The HEAT mode is the step in which the samples are carried through the “Supercritical Point”. Both the pressure and temperature will steadily rise and be maintained above CO2 supercritical point parameters of 1072 psi and 31°C.
  • The process chamber pressure will increase and go beyond 1072 psi and will stabilize in the range of 1350 psi (+/- 5%). When the temperature reaches 31°C, the system has achieved the supercritical point and will stay in this state for a period of four minutes with the HEAT led blinking.
  • At the end of the 4 minutes, the system will automatically advance into the BLEED mode. The HEAT led will stop blinking and the BLEED led will illuminate. The process chamber will begin to bleed the internal chamber pressure at an average rate of 100 – 150 psi/min.
  • At approximately 360 – 400 psi, the system will automatically advance into the VENT mode. The BLEED led will turn off and the VENT led will illuminate. The chamber pressure will then more rapidly drop back towards “0” psi.
  • The chamber lid may now be removed by alternatively and evenly loosening all the knurl nuts using the spanning wrench in a “reverse star pattern”. Carefully place chamber lid on a soft surface (clean room tissue) face down. Once the chamber lid is removed, always protect the face in contact with the chamber.
  • The samples can now be removed from the process chamber. Put the chamber lid back and seal the process chamber with the chamber lid to keep it clean and moisture free.
  • After the final process run is complete, power down the system in the following sequence : chiller power off, then condenser power off and then chamber power off.
  • Go in grey room at back of the tool to close the CO2 bottle.
  • Log OFF the tool on Z14 computer.