Table 1 |.

Troubleshooting table.

Step	Problem	Possible reason	Possible Solution
Procedure 1
7	Printed substrates damaged during the release by a rubber blade	The rubber blade is dull or too thick to make clear-cut release of the printed substrate	Sharpen the edge of the rubber blade. A sharp blade can easily slip between the substrate and the build head
9, Box 1 (stepS 1, 2)	Unwanted connection between electrodes	Silver paste residues remain between the electrodes which form the electrical connection	Dry silver paste completely and clean the probe surface with a stainless steel blade until the residues are completely removed
11	Inoperative μ-ILEDs	Soldering between the μ-ILED and the electrodes is not secure	To prevent this problem, check if the amount of solder paste is adequate and two electrodes of a μ-ILED are precisely positioned on both electrodes of the 3D-POPs in Step 10. In case of trouble, remove the μ-ILED from the silver electrodes using a tweezer and re-solder it. If there was damage to the electrodes, fill in the silver paste again before proceeding.
12	Damage of the electrodes/substrates while detaching the probe from Kapton tape	Kapton tape is too sticky	Reduce adhesion by scratching the surface of the Kapton tape several times with a stainless-steel blade
Procedure 2
10	Failure in assembling the connectors	Excessive epoxy can fill the female connector, thereby blocking the connector holes	Apply minimal epoxy around the connector in Step 17 to prevent excess filling of epoxy into the connector holes
Procedure 3
3, 4	Probe bends or shears upon insertion into the brain	If the dura is not completely removed or if the probe is not completely perpendicular to the site of insertion, the probe may flex during insertion.	Ensure the probe is perpendicular to the skull surface and the dura is completely removed before insertion
4	Probe shifts position during implantation	If the probe is not securely held in the adapter, the probe may move during implantation	Check before inserting probe that the probe is securely attached to the stereotaxic arm
	Widespread damage, bleeding, and inflammation around implantation site	Drill penetrates through the dura	Ensure magnification levels of the surgical scope during drilling are sufficient to visually assess whether the dura is intact after drilling. Excessive bleeding and visible brain tissue damage are signs that the drill has penetrated beyond the dura and has damaged the brain.
9	Metabond enters the drill hole, directly contacting brain tissue	The initial later of Metabond is a very thin viscosity or the researcher applies Metabond too close to drill hole	Apply Kwik-Sil to seal the hole at the implantation site prior to applying Metabond.
11, 18	Damage to connector or 3D-printed probe holder	Cagemates chew the connector	Ensure that the entire implant and connector are covered with Metabond leaving only plug openings or choose to house mice separately
13	Large portions of the skull are visible around the cement cap	The incision is too large for the cap size	Apply a suture to the posterior end of the incision to ensure proper healing
20	BLE module is disconnected prior to or during behavioural assay	Plug connection is too loose allowing the animal to remove with normal grooming or locomotion	Gently bend the prongs of the connector to create a tighter fit with the plug