The last couple of decades have seen a revolution in human-machine interfaces (HMI). Since the iPod, people have been looking to transform their user experience with everyday products to get that smarter, more intimate experience. But the user interface transformation goes beyond consumer electronic devices. Cars, household appliances, public terminals, home heating controllers and more are part of this revolution in interface design and, as with all revolutions, there are casualties.
The HMI of any electronic product, whether consumer or industrial, can mean the difference between bliss and frustration, determining the product’s success or failure. Users are increasingly knowledgeable and selective; just walk into any electronics store to see exactly how much consumers like to try before they buy. Of course, mechanical switches and keys have been eliminated in many products. Resistive touch screens and panels have been replaced by capacitive touch panels. Whilst far from being the first to feature the technology, smartphones and tablets have made all of us aware of the elegance and limitations of capacitive touch controls. At their most sensitive, capacitive touch is prone to false triggering. When they’re not sensitive enough, they’re frustrating to use. Moisture can cause problems, as can electrical noise, and if you’re wearing gloves that can be a problem too.
There’s a further challenge to HMI designers of electrical and electronic products: devices are becoming more complex to meet the increasingly-sophisticated customer demand. In an effort to gain competitive advantage, products continually offer more functions. With each new function, there needs to be some way to control that function, so in the traditional sense that means more buttons or menu items. Gesture recognition has come to the rescue to replace some buttons with a small number of gesture controls, but users have to go through a learning experience to accomplish basic controls. Even so, Transparency Market Research is forecasting a 20.3% CAGR for gesture recognition technology between 2015 and 2021, reaching a market value of 29.1 billion USD by that year, largely driven by the consumer sector. If this demonstrates anything, it’s that today’s HMI experience does not deliver the perfect touch that consumers crave.
One approach to simplifying the HMI is to make better use of tactile based controls, especially in the Z‑axis. If you can produce a signal in proportion to the pressure applied by a finger or stylus, and do that in a precise, reliable and repeatable way, you have added a new dimension to the way in which devices can be controlled. A simple touch button can now be more than a switch; it can become a switch and intensity controller in one, varying the volume in a sound system, the brightness of a light, or the speed of a motor as the force of the applied touch increases. Now, a combination of one-handed squeezes and presses can make a simple surface replace the myriad of traditional buttons needed to be used in a complex sequence or in combination to activate all the features product designers want to pack into their new products.
Force sensors based on Quantum Tunnelling Composite (QTC), an economical, flexible polymer, are a unique way to overcome the limitations of other sensor technologies. With no force applied, QTC is a perfect insulator. As pressure is applied, the material becomes progressively more conductive and, because it can be formed into virtually any size, thickness or shape, the potential applications are unlimited. Interfaced to appropriate electronics, QTC can be used as a simple, durable and sensitive switch, or as the basis of a progressive control for speed, volume, brightness or any other system variable. The desired sensitivity can be optimised for each application. The material is ideal for creating cost-effective and responsive multi-touch panels or displays, where each touch point may be individually tuned to produce the desired experience. Noise immunity and good temperature stability are other QTC benefits, and firmware and software are relatively simple, reducing development time.