What is Conductive Paint? Pros, Cons, and Applications
Electronics have been integrated into our daily lives to a degree where we can hardly imagine living without them. From automobiles to household appliances and even our train tickets, the use of electronics in even the most mundane aspects of our life has given us a great deal of convenience.
This “integration” of electronics to everyday objects is the main objective behind the development of conductive paint. The possibility of conductive materials being delivered in a medium as flexible as paint can change our entire idea of what circuits are and how they can be used. What exactly is conductive paint and how does it work?
What is conductive paint?
As its name implies, conductive paint is a type of paint that is electrically conductive. This involves the combination of conductive particles, such as metals or graphite, and a liquid medium. The particles in question need to be ultra-fine to retain the characteristic wetting and binding of regular paint.
Current is delivered through conductive paint by jumping from one nanoparticle to another. This means that these particles need to be packed very closely together to provide bridges for the transmittal of charges – like a pearl necklace. This means that there is an element of randomness involved in determining how well an application of conductive paint is.
Is there a difference between conductive paint and conductive ink?
If you’ve ever tried searching for conductive paint, you may find that the terms ‘conductive paint’ and ‘conductive ink’ are used interchangeably. This is because they are essentially the same thing with minor differences in how they are used and their suitable applications.
By standard conventions, paint is used in industrial applications in a manner where it sits on top of the substrate. It is often applied by spraying or brushing. In contrast, ink is printed onto the substrate in a manner where it penetrates the surface of the substrate, like in paper or fabric.
In many ways, the distinction between paints and inks has always been ambiguous. If you’re trying to pick between conductive paint and conductive ink, what often matters is the substrate to which you are going to apply it to and the manner of application. Conductive ink is more suited to small-scale applications, while large projects are likely more appropriate applications for conductive paint.
Types of conductive paint
There are a lot of conductive paint products out there, but we will make a distinction between two types based on the different conductive materials used in each. Basically, the current is conducted through either metal particles or graphite particles.
Metal-based conductive paint
The more common type of conductive paint contains nanoparticles of metal is a solvent-based medium. The most common types of metals used for this purpose are either copper or silver, both of which are highly conductive and malleable or “soft” metals.
The advantage of using metal particles as a base for conductive paint is that they are capable of supporting higher current transmission. This is because of the inherent conductive of metals, particularly those that are typically used in conductive paint. For high load applications, metal-based conductive paint is a more reliable option.
Metals do not come without drawbacks. They are prone to oxidation, so an application of metal conductive paint may have a limited shelf life. They also typically require a solvent-based medium to simulate the characteristics of paint, which poses hazards in terms of flammability and ventilation.
Lastly, some of the more valuable metals are hard to source and subject to fluctuations in market price. This doesn’t matter much if you’re just looking for conductive paint for one-time use, but it’s something you may want to consider if you plan on using conductive paint in a recurring manner.
Carbon-based conductive paint
An alternative to carbon is graphite, a crystalline form of carbon. Graphite has long been used as an alternative conductor to metals because of its abundance in nature, resistance to oxidation, and better heat stability.
As a material for conductive paint, graphite is merely ground down to ultra-fine particles and mixed with a fluid medium. Since graphite does not oxidize when exposed to moisture, it allows for the use of a water-based medium to create conductive paint. This makes paint that is solvent-free and less toxic. Graphite-based conductive paint will dry at room temperature and requires no curing.
However, it also means that graphite-based conductive paint applications are not waterproof, although this can be remedied by the application of acrylic varnish or any waterproof coating. There are also certain materials, such as some plastics, that are hydrophobic in nature and will resist binding with water-based paint.
The biggest drawback to choosing graphite over metals as the conductive medium is the inherently lower capacity of graphite to transmit current. Unlike the ion migration phenomenon in metals, graphite relies on charge localization for its conductive characteristics. This is a much slower mechanism for transmitting a charge, which severely limits the extent of application of a graphite-based conductive paint.
Pros and cons of conductive paint
Conductive paint may be revolutionary in terms of versatility and ease of use, but all industry experts agree that they aren’t bound to replace solid conductors anytime soon. Here are some of the strong points of conductive paint, as well as its major limitations.
Conductive paint has made it possible to integrate electrical circuits in a medium that would otherwise have been impossible using old conductor technology. This includes flexible media like paper and fabric.
This flexibility also extends to how conductive paint is applied. It can be painted on manually with brushed, sprayed, screen printed, or printed using inkjet technology. This versatility in application makes conductive paint a viable component for automated manufacturing processes.
Easy to use
Not everyone has the technical knowhow to build circuits out of wires, but even kids know how to use paint or ink. This unparalleled ease of use has made conductive paint a valuable tool in education about electronics and circuits, as well as a tool for quick repairs.
Not as conductive as solid conductors
The harsh reality about conductive paints or inks is that they will never be as conductive as a solid piece of conductive material. Current transmission relies on contact between adjacent particles of conductive particles, forming a continuous bridge from one terminal to the next. This is not an issue with a solid piece of metal wire.
However, there’s an element of randomness in how well conductive paint can replicate this effect. There are also variables to consider, such as the thickness of paint application and curing time. In any case, there will always be a degree of inefficiency in charge transmittal when using conductive inks.
Although the lack of rigidity of conductive paint gives it whole new dimensions of versatility, it also means that it lacks the durability of solid conductors. In most cases, conductive paint is not applied to objects made for rugged use. There’s still a silver lining behind this drawback, though – the fact that circuits made with conductive paint are easy to repair.
Applications of conductive paint
Conductive paint is a technology that has been around for a long time, but its adaptability has been slow to grow. The main hurdle to its acceptance is the fact that it’s seeking to replace traditional electric circuitry – a long-established technology that we’ve come to be highly dependent on. Thus, the use of conductive paint has been mostly restricted to novel applications and those that are deemed to be non-critical. Here are some of the ways in which conductive paint is currently being used:
Education about electronics has the potential to be revolutionized by the use of conductive paint. Instead of using wires and breadboards, students can simply draw circuits of paper to connect electrical components with a power source.
This greatly streamlines the process of learning about circuits and makes it more fun and accessible for young students. More so, circuits made from conductive paint don’t even have to look like circuits. This gives students some artistic liberty in how they choose to design their circuits.
Conductive paint has made it possible to integrate electronic circuitry in objects as light as paper. RFID tags such as those made for train tickets and access cards typically have circuitry made with conductive paint. This may not be immediately visible as they can be embedded inside the cards, despite their remarkably thin form factors.
RFID tags are some of the finest examples of the utility of conductive paint, integrating electronics in objects that were deemed to be impossible before.
Soldering a process by which electrical components are joined together by solder or a piece of molten filler metal. Aside from joining them physically, a solder also provides a conductive bridge. However, old-fashioned soldering requires exposure of filler metal to high temperatures. This is a somewhat delicate process that can be dangerous to someone inexperienced.
Cold soldering using conductive paint eliminates the complexity and hazards of hot soldering. With cold soldering, you can create conductive bridges across electrical components in just a few minutes with no technical skills, and without the use of any special equipment.
Conductive paint can be used as a tool for making quick repairs in damaged electric circuitry, especially if you have neither the time nor the materials to come up with a more permanent repair. Take note that conductive paint should not be used as a replacement for actual electrical wires or other electrical components. However, they should work well enough for when you are in a tight spot, like when your car breaks down or a kitchen appliance becomes damaged during the weekend.
One of the most highlighted potential uses of conductive paint is in the field of wearable technology. It’s easy to see the appeal – before conductive paint, there was no way to integrate electrical circuitry in fabrics in a way that didn’t make them heavy or unwieldy. The potential of this avenue of conductive paint use is yet to be explored, but there has already been talk of clothes that can detect temperature and humidity which can then relay the data to a smartphone. The possibilities are unusual but certainly exciting.
How to make DIY conductive paint
As you’d expect, conductive paint is a bit more expensive than regular paint. If you don’t feel like spending $30 for a small cylinder of conductive paint, then you can make one yourself with just a few easy-to-access ingredients.
There are a lot of DIY tutorials online on how you can make your own conductive paint. For almost all these tutorials, the conductor of choice was graphite powder. This is much easier to buy than metal nanoparticles.
You will then need to use a non-conductive liquid vehicle to suspend the powder and spread it densely and uniformly. There are several different options for this. You can stick to standard white glue, but some have gotten more success by using acrylic paint. In either case, you want to attain a consistency that is very thick but can still be applied in thin and consistent coats.
Making your own conductive paint is a lot cheaper than buying. With a white glue vehicle, you can make white glue that is about ten to twenty times less expensive than those that are commercially available. The quality of DIY glue is comparable to store-bought ones, as long as you are using the same conductive material.
Conductive paint remains a somewhat novel material with potential that is yet to be explored. The beauty of conductive paint is that it’s very accessible – it’s cheap, easy to use, and you can even make your own batch out of some store-bought materials. It’s still massively limited in terms of its conductive properties, though.
While conductive paint isn’t going to replace actual solid conductors anytime soon, it’s not a far-fetched thought that it could have some niche applications. Finding this niche is perhaps the most immediate challenge that this technology faces.