The Role of Conductive Inks in Additive Electronics Manufacturing

In a future characterized by flexibility, stretchability, sustainability, and affordability, conductive inks serve as tools to foster electronics innovation. In this blog, we will explore the role of conductive inks in printed electronics.

Conductive inks are printable materials that are capable of conducting electricity. These liquid inks contain other conductive materials, such as silver nanoparticles or copper and carbon particles, and enable electrical conduction. Most inks aren’t conductive right from the beginning — they need to be processed to evaporate the solvents, which strengthens the connection between the metal particles. After the printing process, they are cured in different ways to render them electrically conductive. Typically, the main curing process we use on V-One for low-temperature inks is thermal curing. This process applies heat to initiate polymerization, solidifying the ink and changing the volume of the traces. However, there are alternative methods for processing conductive inks, such as ultraviolet (UV) curing. UV curing exposes the uncured ink to UV light, converting the monomers to polymers, which hardens the liquid.

To learn more about what conductive inks are made of, see What is Printed Electronics? Conductive Inks.

The increasing demand for flexible and stretchable electronic devices requires conductive materials that can satisfy the characteristics of the devices. Traditionally, subtractive manufacturing processes like chemical etching require an extensive production process that is costly, wastes material, and is environmentally harmful. Conversely, conductive inks are used in additive manufacturing processes — providing an extensive list of benefits to users:

Because conductive inks are additive in nature:

• They accelerate the design and iteration stage for developing electronics. 
• They avoid multi-step procedures related to chemically stripping materials (keep reading — there’s more on this process below.)

Instead, they utilize a more streamlined process of printing only what’s needed, where it is needed. This approach eliminates material waste and enables users to develop and test their prototypes faster.

Conductive inks are comprised of a wide variety of functional materials, providing users with a diverse range of application compatibility. With various resistance thresholds and temperature ranges, conductive inks allow for compatibility with flexible and stretchable applications on a wide variety of films and substrates. Here are a few examples of the inks and their potential applications:

• Silver conductive inks are easy to print and offer excellent conductivity and low resistance, making them ideal for applications requiring high flexibility. Typical applications where silver conductive inks are used include aerospace electronics, alternative energy solutions, biosensors, RFID tags, and automotive sensors.
• Silver/silver chloride (Ag/AgCl) inks are an environmentally friendly option, commonly used in biomedical electronics. Their smooth finish and ability to achieve different resistance and sensitivity levels by adjusting their ratio make them specifically suitable for on or in-body applications like health monitoring patches and sensors.
• Carbon inks offer high thermal stability at a lower cost compared to silver conductive inks. Their chemical inertness makes carbon inks suitable for printing resistors and conductors on non-conductive materials such as plastics, ceramics, and paper. Carbon-based inks are useful for applications like windshield defrosters, resistors, computer keyboards, and capacitive sensors where conductivity and stability are required. 
• Gold and platinum conductive inks offer very high electrical conductivity and longevity, and are used in applications where the higher conductivity can justify the high price. The durability of these electrically conductive inks can be attributed to their resistance to corrosion and oxidation. Some common applications where gold and platinum conductive inks are used include photovoltaics and thin film transistors. 

Subtractively manufactured electronics involve chemical etching, a process that subjects material to chemicals to remove excess material until the final form is obtained. This process generates significant material waste and also exposes handlers to toxic chemicals such as sodium hydroxide or ferric chloride. 

A much safer option is printing conductive inks additively onto a substrate or film in the desired pattern, resulting in no exposure to toxic chemicals or creation of material waste.

There are numerous applications for conductive inks. We’ve highlighted a few below that have been developed on our materials dispensing systems, NOVA and V-One:

This project involved designing a remote-controlled robotic hand, printed using a highly conductive stretchable silver ink from Celanese. The process of building a remote-controlled robotic hand involved designing strain gauges that could stretch while maintaining good conductivity and exhibiting a measurable change in resistance. Using this stretchable conductive ink opens the door for designing strain gauges on nearly any flexible material.

This application saw the full design and build of an insole with a force-sensitive resistor capable of detecting pressure and weight distribution in a shoe. Using the same stretchable silver conductive ink as the robotic glove above, traces were printed onto a sheet of thermoplastic polyurethane (TPU), which then comes into contact with a carbon sheet under pressure, allowing for resistance to increase in various regions of the print. 

Another industry where we continue to see the application of conductive inks flourish is biomedical health monitoring. In our webinar Printing Biomedical Sensors, we demonstrated printing a biomedical sensor using Creative Materials’ 124-36 silver-silver chloride on TPU. 

Didn’t get a chance to attend the webinar? Watch the recording on our YouTube channel:

Another common application for conductive inks is printing RFID tags. In this example, the tags were printed using Copprint’s LF-301 nano copper ink on paper in the desired pattern. This process resulted in better performance than an off-the-shelf tag we purchased from a market volume leader in RFID. With NOVA, we were able to produce one fully printed RFID tag antenna in less than 15 minutes.

Each ink has its own unique specifications and applications. Making a decision on which ink to choose can seem intimidating, so we are going to help simplify this process for you:

When choosing an ink, there are a few main aspects to consider to ensure your application achieves the results you're looking for. The main consideration is what you're trying to achieve with your application. This main decision will lead to other secondary considerations, such as the substrate you plan to print on, the technology you intend to print with, and your budget. For a detailed breakdown on ink compatibility, see our Compatibility Guide for Inks and Substrates.

Some conductive ink suppliers include:

• ACI Materials
• Creative Materials
• Copprint
• Celanese
• Novacentrix

If you have questions about ink compatibility with our NOVA or V-One dispensing systems, please contact us at support@voltera.io. 

The innovation of technology can’t exist without the innovation of processes. As electronics continue to move into a more flexible, sustainable, affordable, and reliable future, conductive inks serve as tools to make these innovations achievable. 

Book a meeting with one of our application specialists to discover why a NOVA or V-One dispensing system could be a game changer for your printed electronic applications.

Conductive inks are printable liquids that conduct electricity after processing. They contain conductive particles or flakes (commonly silver, copper, or carbon) suspended in a liquid system. Across different types of conductive inks, you are typically looking at a combination of filler (conductivity), binder (adhesion and mechanical integrity), and vehicle (printability).

When looking at conductive inks' advantages and disadvantages, the biggest advantage is formulation versatility, as conductive inks can be designed around different conductive materials and performance targets. The main “cons” are usually practical constraints rather than deal-breakers: material cost can vary widely by ink system, and most conductive inks still require defined post-print processing (drying and curing) to reach final conductivity and stability for your application.

Thermal curing uses heat to evaporate solvents and solidify the ink, which can reduce the trace volume as it cures. UV curing uses UV light to polymerize monomers in the ink, and UV-cured inks retain their full volume since nothing evaporates. Which cure method you need is dictated by the ink chemistry.

Use a conductive polymer when you need a trace or sensing layer that performs well on flexible substrates, especially in printed electronics applications like flex sensors. We’ll also sometimes use a combination of materials in one build, for example, pairing a silver ink layer with a conductive polymer layer in a thin-film pressure sensor. The right choice comes down to what’s compatible with your substrate and curing constraints, plus the printing techniques you’re using.

Take a closer look at what our customers are doing in the industry.