Have you ever wanted to create something with your 3D printer that included electronic components? Perhaps sensors, conductive traces or shielding against radio frequency noise?

The FFF/FDM conductive filaments for 3D printing have been designed for users interested in combining 3D printing and electronics. Conductive assemblies that integrate switches, potentiometers, LEDs, capacitive touch sensors... All this and much more is possible thanks to them.

Specifically developed to enable 3D printing of electronically conductive components, conductive filaments are materials that are very easy to print and compatible with almost any FDM/FFF 3D printer on the market.

Applications

Its applications are many and varied, but the following stand out in particular:

Sensors

The conductive filament can be used to create capacitive (touch) sensors used in a wide range of electronic products that are used in everyday life; It is an excellent material for the design of human interface devices (stylus pens for mobile phones and tablets).

Video 1: Pointer pencil. Source: Proto-Pasta.

Capacitive sensing sensors can also be used to measure proximity, position, humidity, liquid levels, and acceleration.

Conductive tracks

Another application of the conductive filament is in the creation of circuits conducting electricity for uses in electronics which, in the case of flexible conductive filaments, will also be applicable to flexible electronics.

Image 1: Driving circuit. Source: Recreus.

Traditionally, in order to add conductive circuitry to their creations, 3D printing enthusiasts had to design parts with the necessary grooves to add copper wire after printing. With the conductive filament, the wiring can be printed simultaneously with the construction process of the piece.

Shielding against radio frequency noise and electromagnetic interference

The high conductivity offered by the conductive filament is not only excellent for 3D printed circuits and sensors, it is also useful for use against EMI (Electromagnetic Interference) and in very important RF (Radio Frequency) shielding applications in a wide range of applications. range of industries. EMI/RF shielding is used to block the electromagnetic field and radio frequency electromagnetic radiation within a space; It is important to use EMI and RF shielding in hospital, laboratory, or aerospace industry settings to protect against competing signals, as these can lead proprietary equipment to give false measurements. EMI/RF shielding accomplishes this by blocking AM, FM, TV, emergency services, and telephone signals. Conductive filament is ideal for designing RF/EMI shields used in highly custom items.

Tips for use

Designed for use with prints intended for room temperature operation and for use on low voltage, low current projects only (not to exceed 12 volts ), conductive filaments should be avoided for power supply exceeding 100mA.

Printing with conductive filaments (PLA) is almost as easy as printing with standard PLA. It is not necessary to have a 3D printer with a heated bed, although if you do have one, it is recommended to use the heated bed at 50-60º C since greater adhesion is obtained.

Possible contamination of the conductive filament with dirt from hands or dust from the environment should be avoided as much as possible, so it is recommended storage in a dry place and away from these and/or other particles. It is also recommended to wash your hands before and after use and treat it with gloves. The user should avoid prolonged exposure to moisture.

A nozzle is recommended for printing conductive filament of at least 0.4 / 0.5 mm. The 3D printer nozzle should always be washed before and after using the filament to avoid printing complications. Conductive filament has a tendency to stick to brass nozzles so it is recommended to clean the external surface of the nozzle before printing with oil (technical or domestic) or lubricant to reduce build-up of the material on the outside of the nozzle during printing. You can also use plastic-repellent paint.

Image 2: Plastic repellent paint. Source: Sliceengineering.

The intrinsic properties of the conductive filament are such that it should not be left idle in the extruder of the 3D printer (while not printing) as it can expand and cause clogging of the nozzle ( clogging). Therefore, after printing, the filament should be removed as soon as possible from the extruder and use cleaning filament. cleaning.

Image 3: Cleaning filament. Source: Smart Materials.

It is also very important to print at the recommended temperature, since if you print at a lower temperature, the viscosity of the melt will not be optimal, so it will expand and clog the nozzle; and in case of printing it at a higher temperature, it will result in a partial degradation together with a substantial aggregation of nanomaterials also producing nozzle clogging.

In the event of a total obstruction of the nozzle, try to unclog it by heating the nozzle to 200ºC and try to remove the obstruction with a copper wire, or try to melt ABS or PLA (rigid filaments) to drag the material trapped, or soak it in acetone, etc. In case of not being able to solve the problem, it will be necessary to change the nozzle for a new one. To avoid this, all the advice mentioned above must be taken into account.

On the other hand, it is also very important to have the base of the 3D printer perfectly level, otherwise a significant amount of material will accumulate on the external surface of the nozzle, which when solidified will clog the flow of the melt. Therefore, the outer surface of the cooled mouthpiece should be cleaned with alcohol if this happens.

Conductive filaments on the market

Conductive PLA (Proto-Pasta): With a softening temperature similar to PLA, Proto-Pasta's conductive filament is more flexible, but has less adhesion between layers. Feasible to control any element through a 1Kohm resistor, it is ideal in low voltage circuits, digital keyboards that require low conductivity, arduino, touch sensors, robotics and electronics.

Koltron G1 graphene filament (Addnorth): Doped with Aros Graphene, a graphene developed and patented by the company Graphmatech and with a matrix based on polyvinyldiene fluoride (PVDF), an advanced plastic that has excellent mechanical, chemical and thermal properties, the Koltron G1 filament has a volume resistivity of only 2 Ω-cm.

Filaflex Conductive (Recreus): Next, we will take a closer look at this filament.

Filaflex Conductive (Recreus)

The Conductive Filaflex is a flexible TPU elastic filament. With a 92A hardness, it reaches 100% elongation at break. After stretching it returns to its original shape, without deforming or breaking, presenting excellent mechanical properties. The Filaflex Conductive filament offers a volumetric resistivity of approximately 3.9 Ω-cm, much higher than that of other conductive filaments.

From the manufacturer itself, we are offered a series of tips capable of solving any questions that may arise when printing with this filament:

1. Hardened nozzle: It is not necessary to use it with the Filaflex Conductive filament. However, in case of intense use, it would be recommended to avoid excessively rapid wear of it.
2. Security: Printing with Conductive Filaflex filament is totally safe and will not damage the printer, but to keep it in optimal conditions it is advisable to clean the nozzle very well when you finish printing with the filament. Thus, any type of rest that may have remained in the hotend will be eliminated. Using X after printing is an extra step that will also help with cleanup.
3. Conductive material: For the filament to be conductive, Recreus informs that they use a special formulation that contains carbon black and it is this element that gives conductivity to the Filaflex Conductive filament.
4. Flexibility: After printing with the filament, its characteristic elasticity is not lost. The resulting final piece will always be flexible and electrically conductive, keeping its other properties intact.
5. Shore Hardness: It has a Shore hardness 92A, making it compatible for use in almost any printer (bowden included).
6. Resistance: Filaflex Conductive has an electrical resistivity of approximately 3.9 Ω-cm, but to ensure compliance with its functions, the user must take into account that the resistance changes depending on the print. In addition, we must also consider the electrical resistance of the circuit and do not forget that the filament is designed for low current applications.
7. Adhesion between layers: Due to its high carbon load, the heat will be dissipated very quickly and the adherence of the piece will be affected depending on its geometry. By adjusting some printing parameters (speed 20-25 mm/s, temperature 240-255 ºC, don't use layer fan) the user will be able to solve such rapid dissipation.

Video 2: Flexibility and conductivity with Filaflex Conductive. Source: Recreus.

In conclusion, conductive filaments are materials specifically designed to allow 3D printing of electronically conductive components using almost any FDM/FFF 3D printer available on the market, expanding the capabilities of additive manufacturing or 3D printing and allowing to shorten the path from development to commercial application.