DC Etching
Recommended for 0.10" W wire: 4.0–5.5V, 3–6M NaOH(aq)
The W wire should extend through the centers of both gold rings, therefore
requiring a sample piece 2.5–3" long. If the wire is not long enough,
look at AC Etching Procedure, Step #1.
Directions:
1. Set the micrometer to 3.0 before loading the wire.
2. The W wire is held by a steel wire collet, which is located above the gold rings. Open the collet by depressing the spring-loaded screw. Insert the wire into the center of the collet. See picture on right.
3. After loading the wire, check to see if the wire extends through the center of both rings by adjusting the distance with the micrometer. If not, depress the spring-loaded screw and readjust the wire.
4. Check to see if the planes of the gold rings are perpendicular to the wire. Readjust wire and rings as needed.
5. Switch on the Schrodinger’s potentiostat located on the far right side of the front panel. Launch the sharpener application by going to Start – Programs – Obbligato Objectives – Schrodinger’s Sharpener . The control panel of the sharpener appears on the computer screen.
6. Submerge both gold rings in a 50mL beaker of NaOH(aq) and slowly lower the beaker to suspend lamella film in the rings.
7. Monitor the contour of the tip with the video camera by pressing the Video button. Pressing the Lamp button can also illuminate the light. Turning the micrometer can make adjustments of tip contour during the etching process. The Display and Format menus can also change the qualities of the video image. To adjust the position of the camera, release the lock on the positioning arm and bring the camera lens toward the rings. Lengthening or shortening the extension tube length by turning the extension tube about its screw thread can remedy focusing. Once the desired image is obtained, lock the positioning arm.
8. On the control panel on your screen, use the vertical slide bar found under Etching Properties and set the desired etching voltage between 0–8.0V. During the etching process, the actual voltage will be displayed in the Current Status area.
9. At the end of the etching process, both a visual and audio alert will
go off. The Visual alert will flash the program’s icon
in the Windows control bar, while the Audio alert will sound a bell
through the computer system. Pressing the Stop Alarm button can
stop the Audio alert. By checking on the appropriate boxes in
the Alerts area, you can enable or disable either alarm.
10. With the Etching Voltage set and the W wire in place, press the Start
button to begin the etching process. As the etching process continues,
the current passing between the wire and the gold cathode can be monitored under
Immediate Current. Here, the voltage will slowly drop to zero.
The green Etching LED should be flashing and the red Brake LED
should be off.
11. During the etching process, it is normal to have the lamella film brake. To remedy this, simply submerge the rings in NaOH(aq) and continue etching by pressing the Start button. Occasionally re-submerging the rings in NaOH(aq) during the etching process replenishes the [OH-] and is very desirable. After re-submerging the rings in NaOH(aq), the voltage read under Immediate Current will read the maximum voltage of 10.0, but will quickly drop back to the previous etching voltage.
12. When the W wire is done etching, the alarm will sound. Bring the new tip away from the film by turning the micrometer. Using a pipette, rinse the tip with drops of distilled water, starting at a point on the wire and letting the water drip off of the tip. This helps to prevent newly made tips from having a curled end.
13. Press the Stop Alarm button to turn off the Audio alert.
14. Set the micrometer back to 3.0 and remove the W wire.
15. Turn off the video camera and/or lamp by pressing the Video and Lamp buttons.
16. Rinse the gold rings by submerging them in a 50mL beaker of distilled water and dry carefully with a paper towel.
AC Etching
Recommended for Pt/Ir wire: 6.0V, 6.0M NaOH(aq), 10% Duty Cycle, 1000µs Repetition Period
Note: Pt and Pt/Ir etching may take from 1–2 hours
Directions:
1. To remedy wire that is too short for etching, take a piece of aluminum foil and wrap it around the end (not the tip) of the wire to create an “extension”. This allows for the shorter wire to be etched. See picture on left.
2. Set the micrometer to 3.0 before loading the wire.
3. The Pt or Pt/Ir wire is held by a steel wire collet, which is located above the gold rings. Open the collet by depressing the spring-loaded screw. Insert the wire into the center of the collet.
4. After loading the wire, check to see if the wire extends through the center of both rings by adjusting the distance with the micrometer. If not, depress the spring-loaded screw and readjust the wire.
5. Check to see if the planes of the gold rings are perpendicular to the wire. Readjust wire and rings as needed.
6. Switch on the Schrodinger’s potentiostat located on the far right side of the front panel. Launch the sharpener application by going to Start – Programs – Obbligato Objectives – Schrodinger’s Sharpener. The control panel of the sharpener appears on the computer screen.
7. Submerge both gold rings in a 50mL beaker of NaOH(aq) and slowly lower the beaker to suspend lamella film in the rings.
8. Monitor the contour of the tip with the video camera by pressing the Video button. Pressing the Lamp button can also illuminate the light. Turning the micrometer can make adjustments of tip contour during the etching process. The Display and Format menus can also change the qualities of the video image. To adjust the position of the camera, release the lock on the positioning arm and bring the camera lens toward the rings. Lengthening or shortening the extension tube length by turning the extension tube about its screw thread can remedy focusing. Once the desired image is obtained, lock the positioning arm.
9. On the control panel on your screen, use the vertical slide bar found under Etching Properties and set the desired etching voltage between 0–8.0V.
10. For AC (pulse) mode, press the Pulse Mode button in the Etching Properties of the control panel. The Duty Cycle and Period options should be illuminated. The Duty Cycle can be set between 1–99% and the Period can be set between 9–1000µs. NA is displayed under Immediate Current in AC mode.
11. With the Etching Voltage, Duty Cycle and Period set and the wire in place, press the Start button to begin the etching process.
12. When the Pt or Pt/Ir wire is done etching, the alarm will sound. Bring the new tip away from the film by turning the micrometer. Using a pipette, rinse the tip with drops of distilled water, starting at a point on the wire and letting the water drip off of the tip. This helps to prevent newly made tips from having a curled end.
13. Press the Stop Alarm button to turn off the Audio alert.
14. Set the micrometer back to 3.0 and remove the wire.
15. Turn off the video camera and/or lamp by pressing the Video and Lamp buttons.
16. Rinse the gold rings by submerging them in a 50mL beaker of distilled water and dry carefully with a paper towel.
For more information, go to Obbligato Objectives .
Updated 8/8/01
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