Transparent Flexible Heaters
As we have become more dependent upon electronic technology for myriad applications in both consumer and commercial markets, their reliability and availability have become more critical. Harsh environments can lead to fogging or freezing, necessitating some means of heating, in some case immediately. The applications can range from display glass to a windshield to a headlight lens.
CHASM TRANSPARENT FLEXIBLE HEATERS
Optical cameras are becoming the technology of choice for collision avoidance, intrusion detection, security, inspection, and process control systems. Cameras can be used to detect precise objects and AI processing can create 3D environment maps in real time enabling drones to fly without collision and autonomous cars to discern a pedestrian from a bicyclist or even a pot hole from a guard rail. All of these systems, along with RADAR and LiDAR sensors, will need to remain active even in harsh weather, so keeping their field of view clear from ice, rain, and condensation is imperative. CHASM’s AgeNT transparent Nanotube Hybrid materials is the only commercially available transparent material capable of delivering the heat density required for these applications without wires.
A transparent electric heating film is typically constructed by “sandwiching” a conductive material between layers of glass or clear plastic, traditionally polycarbonate or acrylic. The challenge here is deploying a conductive material that has both sufficient conductivity AND transparency. Patterns or opaque layers affect visual performance, while insufficient conductivity limits heating speed and range. CHASM’s AgeNT TCF material is available at <10 ohms/square with greater than 90% visible light transparency, ideal for applications in avionics, transportation electronics, kiosks and more.
WHAT IS HEATING FILM?
Heaters are often used to provide a source of climate control, maintaining a temperature in which people are comfortable. However, heaters can also ensure safe operation of devices keeping control panels operational in inclement conditions or clearing surfaces of unwanted snow, ice, or condensation. When the intended application is not suitable for typical heating approaches suck as forced hot air or radiant wires, heating film provide a means of applying transparent electric heating directly to a surface without having any visible means of heat delivery.
There are many applications such as commercial refrigeration systems or touch panels on industrial equipment where a heat source would keep the contents visible or the touch interface active despite condensation or frost buildup. Heating films are used to heat surfaces that need to be cleared of snow, ice, fog or condensation of any kind. They can also be used to heat objects in close proximity. If a particular product requires a “see through” surface that also needs to be cleared of snow, ice, fog or condensation (see list of applications in the section below) and the heating element cannot interfere or visibly block the surface – these are instances when a visually transparent heater is needed. Transparent electric heating can also be used to heat surfaces that are in close proximity of an object that needs heater but also needs to remain visible.
WHAT INDUSTRIES USE TRANSPARENT ELECTRIC HEATING?
Heating films are used in a variety of industries:
- Automotive (personal and commercial vehicles)
- Industrial (HMI screens or any equipment exposed to elements that needs to be heated and remain visible)
- Avionics (lights, windshields)
- Medical (equipment used outdoors or in remote places)
- Retail (refrigerated displays)
- Retail (Refrigerated displays)
- Military (vehicles, equipment and more)
WHAT ARE TRANSPARENT HEATERS USED FOR?
Heating films are used for a variety of applications across numerous industries. Common uses are:
- Safety cameras
- HMI screens for industrial equipment
- Retail (refrigerated displays)
- Medical devices for use in “the field”
- Safety and security equipment
The applications are limitless where product designers and engineers are constantly creating new products that require transparent heaters.
WHAT IS THE HISTORY OF TRANSPARENT HEATERS?
The original “transparent heater” was used to heat windshields of aircraft in World War II. Aircrafts being used in colder climates or particularly high altitudes were susceptible to frost accumulating on windshields and preventing the pilot or other crew members from being able to see out through the frost.
Other earlier versions you might be familiar with are the lines you see on your car rear windshield. Known as a “secondary defogger” these are made from lines of resistive conductors, usually comprised of a silver ceramic material, in or on the glass. While not optically clear, those lines do allow you to see through the windshield enough to see when backing up, while also providing enough heat to defrost the glass.
WHAT ARE THE DIFFERENT TYPES OF FLEXIBLE HEATERS AVAILABLE?
Today’s transparent electric heating has come a long way. There are now optically clear heaters available that can even work with the strict requirements of an optical camera or an HMI screen that demands 100% transparency with zero obstructions. Depending on the application, there are several options available to product designers and engineers today.
As mentioned previously, the type of “transparent heater” that most of us are used to would be the lines we see on the rear windshield of our car. This is generally referred to as a secondary defogger and is “good enough” when used on a flat surface (glass) and 100% optical transparency is not needed.
When more visibility is required, a very, very thin “micro wire” that can carry enough electrical current to heat a surface is meshed across an existing transparent surface. These are sometimes used on headlights or windshields however there are some downsides. If your automobile is relying on optical cameras for its safety system, this option will not work and RADAR or LIDAR will need to be used instead of optical cameras. When used in windshields, this is an effective way to clear the glass but many drivers find they are “driven crazy” by the small wires obstructing their view of the road.
Benefits of Nanotube Hybrid Heaters:
- Flexible, thermoformed for wider range of product designs; integration into headlights and curved glass surfaces
- Up to 2,000 watts/M2; meeting specifications for warming time
- Up to 120 Degrees Celsius
- Obstruction free design (no microwire) for optimal pairing with Optical Cameras. RADAR and LiDAR
- Screen Printable: Quick turnaround on circuit design changes and prototypes; just-in-time production runs
- Lower design cost and lower unit cost, no need for laser ablation, deposition and patterning
When the application requires an obstruction free, optically clear transparent heating film, Transparent Conductive Oxide coatings can be used. This is a transparent conductive material that is widely used for many applications. Fluorine-doped Tin Oxide and Indium Tin Oxide (ITO) are most common. However, these solutions are not flexible and are only effective on flat surfaces, primarily glass. Standard conductivities for these coatings range from <1 ohm/sq to >250 ohms/sq.
If the application requires an optically clear flexible heater, the go-to solution is a nanotube hybrid called AgeNT. This advanced material allows the creation of optically clear transparent heaters on a variety of flexible film substrates. It is comprised of a silver nanowire film encapsulated in a screen-printed carbon nanotube ink creating the resistive transparent electric heating element. AgeNT-10 flexible heaters are capable of operating at 50W for a heater size of 100mm X 160mm (2,000 W/m2).
If you are designing a product requiring transparency and heat, you have quite a few options. The key is to decide how much transparency and heat you require and if your application requires a flat surface, curved, domed or bent. These critical decisions will allow you to make a more informed decision on which heating film (or material to create the heater) is best for your application.
Transparent Heaters for Product Design The Ultimate Guide
When the intended application is not suitable for typical heating approaches such as forced hot air or radiant wires, transparent heaters provide a means of applying heat directly to a surface without having any visible means of heat delivery. Transparent heaters are used for a variety of applications across numerous industries. Learn the basics here.