Prepare Printing Chamber XL

This chapter describes how to prepare the CERES printing chamber XL before a printing session.

Materials

The following materials are needed for the chamber preparation:

Working electrode

A printing substrate (40 mm x 40 mm). The image shows a copper coated PCB with Nickel-Gold finish.

Supporting electrolyte

The standard CERES supporting electrolytes can be used, or any other suitable solution.

Pasteur pipette / measuring cylinder

To measure and place/replace the supporting electrolyte into the chamber.

Chemicals

To clean the working electrode (one working electrode cleaning example is described here).

Clean water

Deionized water could be sufficient, but Ultrapure / type I. (ASTM D1193) water (with resistivity = 18 MΩ·cm at 25 °C) is suggested.

Chamber and substrate preparation

Assembling the XL chamber for printing

1. Insert the teflon spring in the cell body with the taper facing up.

2. Add the substrate holder making sure that it is free to rotate and translate up and down.

3. Add the working electrode with the flat surface facing down

4. Slide the sealing O-ring on the cell lid assembly

5. Place the cell lid assembly on the cell body, making sure to align it properly. You should have to press it slightly to insert it in the body.

6. Assemble the cell with the provided 8 screws and nuts. In order to evenly compress the sealing O-ring, screw the 8 screws progressively until the bottom surface of the cell lid sits on the top surface of the cell body.

7. Secure the potentiostat cable on the side of the XL printing chamber. Check the connections as specified in the cabling routine.

Warning

Do not overtighten at the risk of damaging the PTFE threads

8. Slide the assembled chamber in the base plate as shown (connector on the external side of the plate) and engage the locking mechanism

Attention

The printing chamber XL and the printing chamber V3 have a similar locking mechanism. The base plates and printing chambers must NEVER be mixed at the risk of damaging the CERES system. The height of the components is different between the V3 and XL printing chambers and using the wrong stack height will result in collisions.

9. Place the potentiostat wires in the cable clamp

10. Place the base plate with the chamber in the XY stage sled and connect the lemo plug

Applying potential

1. Fill up the chamber with approx. XX-XX ml of the chamber solution. The liquid level should be 1 to 2 mm higher than the counter electrode. Be aware of evaporation for prints of many hours.

2. If not already open, open the potentiostat tool and select the intended printing solution.

3. Set the potential to the required value.

4. The potential should quickly reach the desired value. The current will slowly stabilize over the course of 5 to 15 minutes. It is advisable to wait at least 5 minutes before starting a print.

What is a good value of current?

While a correct value of potential is necessary for the metal deposition to occur, the current necessary to apply that potential can vary a lot depending on many experimental and environmental variables. For this reason, it is impossible to define a good value of current, and only some loose ranges can be given.

The following orders of magnitude apply:

Current (order of magnitude) [μA]	Time interval
(-)10000 - (-)1000	0 - 5 min
(-)1000 - (-)100	> 5 min
(-)100	stable value

What is a bad value of current?

A faulty connection will result in abnormaly low values of current. Anything absolute magnitude (either negative or positive) of < 10 μA is considered too low for printing.

Substrate Preparation

This chapter is an example protocol for cleaning a gold substrate. Other substrate materials can be used and they may require their own substrate cleaning processes.

1. Take one of the previously diced gold coated wafer pieces with a tweezer from the wafer holder

2. Rinse with acetone from a wash bottle (to remove the protective photoresist and to dissolve the majority of the organic contaminations from the surface)

3. Place inside a beaker of acetone and sonicate it for at least three minutes

4. Rinse the substrate with isopropanol from a wash bottle
5. Place inside a beaker of isopropanol and sonicate it for at least one minute
6. Rinse the substrate with deionized water (ultrapure water is recommended)
7. Place inside a beaker of deionized water and sonicate it for at least one minute
8. Rinse with deionized water (ultrapure water is recommended)

Substrate Loading

Info

It is recommended to load the sample after filling the chamber and applying the potential.

Substrates can be inserted or swapped without the need to disassemble the chamber or, remove/disconnect it from the CERES system.

• To remove a substrate, use a clean pair of tweezers and press and rotate the substrate holder counterclockwise. Remove the substrate from the chamber using a pair of tweezers
• To insert a substrate place it in alignment with the holder (make sure the holder is in the release position: fully rotated counterclockwise) and press and rotate with the tweezers clockwise. The substrate corners should be directly below the graphite lobes of the working electrode.

Chamber cleaning procedures

Before the chamber is used, make sure to rinse the inside of the chamber with deionized water to remove any dust particles.

During long printing sessions, the printing chamber solution should be replaced after 24 hours. It is possible to simply remove the used printing chamber electrolyte with a pipette and refill the cell with fresh solution.

At the end of a printing session, the chamber should be emptied, disconnected and removed from the CERES system. The assembled chamber should be cleaned as follows:

1. Rinse multiple times with deionized water.
2. Fill the chamber with deionized water and let it soak for at least 1 hour.
3. Remove the water, wipe the visible carbon parts with a cotton swab to remove excess carbon particles.
4. Rinse it again multiple times and let it dry.
5. Store the chamber in a clean, dry and dark environment.

In case of very severe contamination, the chamber needs to be disassembled. It is not recommended to disassemble the printing chamber as long as the printing process is working well. If necessary clean as follows:

1. Rinse the chamber multiple times with deionized water.
2. Disassemble the chamber.
3. Immerse the carbon parts in deionized water and let them soak for 1 hour. If available, sonicate the carbon parts in deionized water.
4. Afterwards, wipe down the carbon parts with paper until no black residue can be seen on the paper.
5. Rinse the parts carefully with deionized water and let them dry.
6. Reassemble the chamber.