Fabrication of catheter-type oximeter probe

Procedure:

1. Laser cutter process the copper-clad polyimide, to generate the flexible printed circuited board (fPCB, 1.3 mm x 20 mm) for the probe;
2. Solder the electronics components (LEDs and photodiode) on the surface of the fPCB;
3. Polydimethylsiloxane (PDMS) is mixed with 5% Silc-Pig silicone opaque dye (black);
4. PDMS films are formed by spin-casting (150 rpm) on glass slides;
5. PDMS films are thermally cured in a 70℃ oven for 30 mins;
6. CO₂ laser define the small cuboid structures (L x W x H: 1 mm x 0.5 mm x 0.8mm) for light block;
7. Two light block modules are glued to fPCB;
8. Solder the Teflon-coated copper wires to the end of the fPCB;
9. Insert the electronics module and the thin wires into a flexible tube;
10. Mix the biocompatible silicone prepolymer with 5% of Silc-Pig silicone opaque dye (blue);
11. Inject the silicone prepolymer into the tube, using a syringe;
12. The tube is cured for 12 hours at room temperature;
13. The flexible tube is removed, and the catheter-type probe is generated;
14. Attaching the other side of the Teflon-coated wires to an electronic connector finishes the fabrication of the catheter-type probe.

Materials:

1. Copper-clad polyimide: Cu/PI/Cu, 18/75/18 um, AP8535R, Dupont, Pyralux;
2. Solder paste:
   1. Indalloy 290, Indium Corporation.
   2. SMDLTLFP, Chip Quick Co.
3. PDMS: Sylgard 184, Dow Chemical Co.;
4. Flexible tube: Tygon S3 E3630 Flexible Tubings, Fisher Scientific;
5. Biocompatible silicone polymer: MED-1000, Avantor;

Equipment:

1. Laser cutter: ProtoLaser U4, LPKF Co.;
2. CO₂  laser: ILS12.75, Universal Laser Systems Inc.

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