What is Electric Paint: the composition and application of conductive paints

Conductive inks or conductive paints have been around for a long time. Originally developed for use in printed electronics, applications for these materials were traditionally reserved for printing the PCBs (printed circuit boards) that live inside electronic devices, like the smartphones and computers we use every day. But there is an exciting world of new applications available thanks to advancements in materials science, manufacturing and electronics. We’re obsessed with the capabilities of these materials and wanted to share our knowledge so that you can start bringing this unique set of capabilities into your projects and products.

What are conductive inks?

Conductive inks are paints that are electrically conductive, meaning they conduct electricity. They consist of a conductive pigment, for example, silver, copper, nickel, or various forms of carbon, either suspended as particles or dissolved in a solution. Many different formulations exist, each developed for specific applications with particular material properties.

Although most people use the terms conductive ink and conductive paint interchangeably, there is a technical distinction between the two terminologies and a few different definitions. It’s generally accepted that paint is a material that is sprayed or brushed onto a surface and ink is a material which is printed onto a surface. Additionally, a paint typically describes a material which sits on the surface of a substrate, whereas an ink will penetrate the surface like ink on paper. As is probably now clear, the distinction between inks and paints isn’t always clear, but in general, when working within printed electronics, most materials are referred to as inks, due to the use of printing in manufacturing.

There are many companies that manufacture conductive paints for the consumer market using conductive carbon, graphite, copper or silver as a conductive material. It is worth familiarising oneself with the pros and cons of different conductors before choosing a conductive paint to use. Copper and silver paints can require solvents to remain in suspension so they can be toxic, require curing, ventilation or both. Metal based paints also have particles which can fall out of solution or oxidize, so may have a shorter shelf life or lifespan once applied. Finally, conductive inks made of metals tend to have a much higher price tag making them expensive to use in large-scale applications. Silver conductive paint can be used for paper circuits, but due to the material’s rare nature, silver conductive ink is expensive compared to graphite-based paint, and subject to the market fluctuations around the price of silver itself. Compared to metal conductors like silver, nickel or copper, graphite has a higher electrical resistivity, but it is much easier to source, and can be used in large quantities at a low cost. There are many different paint products and formats developed for different use-cases and applications, these include small bottles, syringes, pens, jars, or even spray cans. There are even online videos for creating ‘DIY conductive paint’ at home.

There are many different ways to apply conductive inks. These include flexography, rotogravure, screen printing, spraying, dipping, syringe dispensing, and stencil printing. The particular material formulation of a conductive ink will vary depending on the printing process or application method, as different equipment will require different properties. Conductive ink printing technology varies dramatically, so different paints are optimized for different temperatures, drying times, flow rate, viscosity, conductivity, resistance, and particle size, among other variables.

A common application for conductive paint that most people will be familiar with is windshield defrosters. However, there are many common use-cases for these technologies, including use in photovoltaics (solar cells), RFID tags, medical devices including diabetes test strips, in-mold electronics, wearable electronics, 3D antennas, flexible hybrid electronics, electronic circuits, touch screens, and many more. But we see an even larger future in the built environment. Conductive inks and paints will find their next set of successful applications within smart buildings and automotive.

At Bare Conductive our focus is on developing use cases in smart buildings and automotive by using conductive inks to create smart surfaces. We use these materials and other printed electronics technologies to create a wide array of sensors. Depending on the use-case, we can select from a multitude of conductive inks to transform ordinary surfaces into smart ones. We also manufacture, use, and sell our own formulation, Electric Paint, which was developed to serve an untapped market of individual engineers and designers looking to prototype with printed electronics.

About Electric Paint

Electric Paint is a water-based electrically conductive paint which was developed as an easy-to-use alternative to industrial conductive inks. The material is non-toxic, water soluble, electrically conductive, and can be used to create small printed circuits and capacitive sensors.

Electric Paint uses a combination of carbon black and graphite in a water-soluble solution to make a conductive water-based paint. It takes advantage of materials and binders used in the food industry to create a carbon ink formula that is solvent free and safe. Carbon is one of the elements, like oxygen or hydrogen, which in turn can take different forms, like diamond or graphite, charcoal or carbon black.  Electric Paint uses two forms of carbon, carbon black and graphite to create the maximum conductivity along with the desired physical characteristics like flexibility and a viscosity appropriate for home use. The combination of carbon black and graphite make Electric Paint a “carbon paint” in industry speak, and they also give it its deep, black color.

Electric Paint air-dries at room temperature so it doesn’t require any curing. It can be applied onto most non-conductive materials with a brush, roller, sprayer, stencil or by screen printing. As the paint dries, the water in it evaporates leaving behind conductive particles on the surface. Electric Paint can be applied to a wide range of substrates such as paper, cardboard, wood, plasterboard, textiles, plastic, glass, and most non-hydrophobic surfaces (any surface that doesn’t repel water), including non-hydro-phobic plastics. When applied in a thin layer, by screen printing onto paper or textiles, Electric Paint is flexible and allows for a degree of bend. Because it is water-soluble, Electric Paint isn’t water-proof and can smudge. This can be controlled by sealing Electric Paint using an acrylic varnish, spray or a water-proof coating. Once sealed, Electric Paint can be covered with another acrylic paint to conceal it completely, or to add color. Sealing the paint doesn’t affect it’s conductivity, as the paint remains intact underneath the sealing coat.

The conductivity of a surface coated with Electric Paint depends on how the paint has been applied and the thickness of the coat. At a thickness of 50 microns, Electric Paint has a sheet resistance of 55 Ohm/square. As a general rule, carbon-based inks like Electric Paint have a higher resistance compared to silver paint or copper based inks. As a water soluble paint, Electric Paint can be thinned by adding water in order to change the viscosity of the material, however, this can affect the conductivity of the paint. Electric Paint dries at room temperature and requires no protective gear, ventilation or specialist equipment.

Why we developed Electric Paint

Bare Conductive spun-out of Imperial College London and the Royal College of Art with the development of Electric Paint in 2009. Bare Conductive’s founders were exploring novel applications for electronic circuits and struggled to get hold of conductive paint samples to test with. Even today, obtaining small samples, or purchasing conductive paints is a non-trivial task. Manufacturers of conductive inks usually require company details to register interest, or demand large volumes or regular order commitments before supplying quotes or samples. Then, like today, getting material samples to experiment with is nearly impossible for individuals, and still difficult for small companies. Additionally, most conductive paints available on the market have hyper-specific application constraints, use toxic solvents, require specialist ventilation or equipment, high-temperature curing or sophisticated printing machinery to use. Back in 2009, there were practically no commercially available materials for anyone wanting to do basic, safe, fast, and low-cost testing with conductive paints.

Unable to get their hands on a material that would suit their technical requirements, the Bare Conductive team developed their own electrically conductive paint formulation, initially called Bare Paint. When they graduated and presented their work, they were inundated with requests from people wanting to purchase the material. Although it had been developed to serve their project’s wider needs, they discovered a massive untapped market, and decided to commercialize the paint. Bare Conductive was founded to bring this technology to market, and to tap into the demand for creating low-cost capacitive sensors.

Over the years Electric Paint evolved from being called Bare Paint, to Bare Conductive Paint, and finally Electric Paint. Today, the material is supplied in three formats: a 10ml tube, a 50ml jar, and a 1L tub. Electric Paint is available for purchase via the Bare Conductive online shop or through a global network of resellers ranging from electronic distributors, to material suppliers, robotics and DIY shops. No forms, specialist tools, or supplier relationships are required to buy or use the material.

Most importantly, the paint is now complemented  by a product range which includes hardware, printed sensors, and development kits. This product suite means individuals can get their hands on the full technology stack required to prototype touch and proximity sensors using Electric Paint. So anyone can experiment with printed electronics and build sensors into their environment, creating large-scale touch and proximity sensors.

At Bare Conductive, we believe capacitive sensing unlocks the biggest potential for Electric Paint: transforming ordinary surfaces into smart ones. Because Electric Paint can be applied to a wide range of inexpensive surfaces, like paper, it unlocks the ability to harness low-cost, high-volume manufacturing processes to produce sensors. This focus on sensing is the main differentiator between Bare Conductive and other conductive ink manufacturers. While most companies producing conductive materials classify themselves as belonging to the coatings industry, Bare Conductive is very much an electronics company focused on a technology stack that transforms printed electronics from passive components, to a platform for making the surfaces and spaces where we live, work, and travel, safer, healthier and more extraordinary.

How we use Electric Paint

Electric Paint can be used for most of the same applications as other conductive materials. It can be painted to create circuits, as seen in the Electric Paint Circuit Kit, or as a conductive coating for shielding, as seen with EMI shielding in guitars. Because the paint dries at room temperature and because of its viscosity, Electric Paint can also behave like glue and can be used as a conductive adhesive for cold soldering non-permanent connections, so two electrical components can be attached without requiring a soldering iron. Electric Paint can also be applied to textiles, expanding the possibilities for integrating electronics into wearables. However, the primary use-case for Electric Paint is in the development of printed capacitive sensors.

What is capacitive sensing and how does it relate to Electric Paint?

Capacitive sensing is a sensing technology that works through the generation of an electric field. This field can detect nearby objects by sensing any disruptions. Although you may not have heard the term, chances are you use this technology on a daily basis as capacitive sensing is the technology used on smartphone screens to detect touch. Capacitive sensing can also be used to detect proximity, making it easy to detect something without directly touching it. This is particularly useful for use-cases where gestures, movement or hygiene are important. When printed over a surface, and connected to the right hardware and software, Electric Paint can be used to create discrete, flexible, and large-scale capacitive sensors. At Bare Conductive we design, develop, and manufacture a complete technology stack, from material (Electric Paint) to hardware and software, that makes producing and customizing capacitive sensors easy.

We have a range of products and development kits aimed directly at consumers, such as the Touch Board (Arduino), Pi Cap (Raspberry Pi), Touch Board Pro Kit and Interactive Wall Kit, which enable users to create sensors using Electric Paint or other conductive materials. These sensors can be used to convert touch into light, sound or data. Printed sensors can also be adjusted and tuned, so it’s possible to turn them into proximity sensors to detect objects at a distance, from behind a substrate or to trigger outputs from afar. When creating sensors, the design, pattern, and shape of how Electric Paint is applied are as important as the material itself, as these factors impact the sensor’s performance. Our Printed Sensor product is an example of an effective pattern, optimising the capabilities of the sensor for proximity sensing.

Making our technology accessible to individual consumers is critical for our technology’s development. Through our community of users, we have seen countless examples of how printed electronics can be harnessed to create interfaces, touch surfaces, and occupancy sensors at both small and large-scale. Printed sensors have been integrated into different environments, from furniture to floors and walls. With the Touch Board, we’ve seen our community create smart environments. From wallpaper that plays a sound when the printed pattern is touched to large interactive surfaces where sensors are integrated within walls to trigger projections onto the surface. The Touch Board, Pi Cap, and our development kits offer an easy entry point for exploring capacitive sensing and the potential of printed electronics in the built environment.

Industrial Applications and Industry Partnerships

At Bare Conductive we see that the audience for Electric Paint remains primarily in the realm of individual consumers, however, the technology stack we have developed serves a much wider market. This is why we are working closely with large industry partners to design and integrate our printed electronics technology into the smart spaces of the future. Our printed sensors allow us to create bespoke interfaces, detect unwelcome guests or gather anonymous data about users, even monitor water leaks. We are transforming the built environment and are currently developing sensors for smart buildings, automotive and smart home. Whether as an interface in your dashboard, tracking a person’s movement in a room or detecting liquid leakage, we have just begun exploring the many possibilities that exist to harness the power of conductive inks and paints in the creation of smart surfaces, and we can’t wait to see where it takes us.