The printing of conductors has recently arisen as a more eco-friendly, adaptable and economical substitute for conventional production methods, as materials are only placed where they are required, reducing wastage. Additionally, printing allows for the mass fabrication of mechanically bending and stretching-tolerant flexible electronics. Conductivity of stretchable materials remains constant even when subjected to substantial deformation; this property is known as high dynamic stability. This makes it easier to produce wearable electronics, which have promising uses in fields as diverse as medicine and athletics.

What materials can be used to make printed stretchable conductors?

There are a number of different materials that can be used to make printed stretchable conductors. Some of the most common materials include:

  • Metal nanoparticles: These nanoparticles are often made of silver, gold or copper. They are highly conductive, but they can be expensive and difficult to process.
  • Carbon nanotubes: Carbon nanotubes are very strong and conductive, but they can be difficult to disperse evenly in a printable ink.
  • Graphene: Graphene is a one-atom-thick sheet of carbon atoms that is highly conductive and stretchable. However, it is also very expensive to produce.
  • Liquid metals: Liquid metals, such as gallium-indium alloys, are highly conductive and can be easily injected into printed structures. These can be difficult to encapsulate and can corrode other materials.

The choice of material will depend on the specific application. For example, if a high level of conductivity is required, then metal nanoparticles may be the best choice. However, if cost is a concern, then carbon nanotubes may be a better option.

How printed stretchable conductors are produced

Printed stretchable conductors can be made using various methods, such as inkjet printing, screen printing and 3D printing. Here is a breakdown:

Inkjet printing:

  • Inks: The key lies in using a special conductive ink. This ink typically contains metallic nanoparticles (silver, gold, copper), carbon nanotubes or conductive polymers acting as conductive fillers and dispersed in a solvent or a stretchable polymer base.
  • Process: The desired design is converted into a digital format for the printer to understand. The printer head is filled with the conductive ink, and the printer precisely jets tiny droplets of ink onto the flexible substrate, following the programmed pattern. The droplets are small, enabling high-resolution printing for intricate designs.

The inkjet printer deposits the ink in a precise pattern onto a flexible substrate. The solvent carries the conductive fillers and other components, allowing the ink to flow through the inkjet printhead's tiny nozzles. It needs to evaporate quickly after printing to leave behind the conductive traces.

  • Advantages: High resolution, good for intricate designs.
  • Limitations: Inkjet inks can be more expensive and require careful optimization for printability and conductivity.

Screen printing:

  • Inks: Similar to inkjet printing, conductive inks with metallic particles or conductive polymers are used. The ink may be thicker than inkjet inks.
  • Process: The desired design is used to create a stencil with the conductive pattern as open areas on the mesh. The conductive ink is placed on top of the stencil and a squeegee, a rubber blade, is firmly pressed across the stencil, forcing the ink through the open areas and onto the substrate beneath. The stencil is carefully lifted, leaving the deposited ink pattern on the substrate.
  • Advantages: Faster than inkjet for larger areas, good for simpler designs.
  • Limitations: Lower resolution compared to inkjet, limited to flat surfaces.

3D printing:

  • Filaments: This method utilizes a specially developed conductive filament. These filaments can be composites containing conductive fillers (like liquid metal droplets) embedded in a stretchable elastomer base.
  • Process: A 3D model of the desired object with embedded conductive pathways is designed using CAD software and a conductive filament is loaded into the 3D printer. The printer follows the programmed instructions, extruding the conductive filament in a layer-by-layer fashion, building up the 3D structure with the conductive pathways embedded within.
  • Advantages: Enables creation of 3D conductive structures, good for complex geometries.
  • Limitations: Resolution might be lower compared to other methods; development of these conductive filaments is an ongoing area of research.

Common considerations

In some cases, a post-printing heat treatment (sintering) might be necessary. This helps improve the electrical conductivity of the printed traces by fusing the conductive particles together. However, it's crucial to ensure the sintering temperature doesn't damage the stretchable properties of the conductor. Moreover, all these methods require using flexible substrates that are compatible with the printing process and the intended application. Common choices include polymers like PET (polyethylene terephthalate) or PDMS (polydimethylsiloxane).

Advantages of printed stretchable conductors

There are several advantages to using printed stretchable conductors. First, they can be fabricated quickly and easily using a variety of printing techniques. This makes them well-suited for rapid prototyping and low-volume production. Second, they can be conformal, meaning that they can conform to the shape of the substrate on which they are printed. This makes them ideal for use on curved or uneven surfaces. Third, they are lightweight and flexible, which makes them comfortable to wear and less likely to break.


Printing conductors have emerged as a more environmentally friendly, versatile and cost-effective alternative to traditional manufacturing methods, as materials are only used where needed, minimizing waste. Inkjet printing offers advantages for high-resolution deposition, but printed track conductivity is limited since the inks used are of low viscosity and concentration. The production of wearable electronics, on the other hand, may be easily and rapidly scaled up to industrial levels using screen printing technology.

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