When it comes to the mystical-sounding field of force sensing, James Lougheed and the team at Exar seem like they’ve got the mystery pretty well figured out. Leading the pack in the development and application of the rapidly-expanding field of force sensing, Exar comes uniquely equipped, as Lougheed puts it confidently, for “providing some exciting methods to replace and improve a lot of the ways that buttons are used in electronics today.” With some obviously interesting prospects on the horizon for force sensing technology, we spoke with Lougheed about what Exar is doing to enable this.
See related product
It’s only fair to ask first: what exactly is force sensing?
“Force sensing is a relatively new technology in the consumer market,” Lougheed begins. And though the technology has been in development for some time, it’s only recently being applied more widely in the truly sophisticated forms that Exar is working to develop. “Essentially, force sensors are discerning the amount of force applied to a specific area of a product. If you look at the Macbook or Apple Watch, for example, when you press something, it can actually measure how hard it’s being pressed.” In a general sense, then, force sensors provide an extra dimensional variable to the interface process, allowing pressure as well as direction or proximity to function as input. It certainly presents a whole new ballgame, to say the least.
The history of force sensing technology in the consumer sphere may not be a long one, but there have been a lot of familiar steps along the way. The piezo-electric sensor, a type of compression-based sensor that employs an electromechanical effect discovered by famous French physicist Pierre Curie in the 1880s, is still common, but remains relatively expensive and, therefore, specialized in its applications. In more consumer applications, like washing machines or ovens, it may be more common to see a variety of old-fashioned ‘membrane’ button or bubble-style switch. More recently, the consumer market has seen a proliferation of what is known as capacitive sensing, which employs a sensor that reacts directly to the capacitance of the human body and allows for a more directly reactive touch-screen-style sensing. Still, especially compared to the level that Exar has developed their solutions in terms of literal force sensing, capacitive sensing is usually considered a shortcut substitute, because it’s still based on a purely ‘on-or-off’ dynamic.
Lougheed relates that Exar’s solutions takes things to the next level and “actually measures the force linearly, in that way really adds entirely new capabilities to button design.” Lots of old strain-gauge-style sensors and much of what is known as force-sensing resistor technology will only work on plastic substrates, and that, Lougheed explains, has kept it from moving into a lot of applications that Exar’s cutting-edge solutions are now well-prepared to handle. Specifically, the company has developed a new kind of solution using thin-film sensing technology that utilizes a resistive material that can be applied on almost any surface, like metal and wood as well as the usual plastic.
Of course, we couldn’t resist asking Lougheed about precisely what to expect in the near future. Specifically, how are we going to see some of this newer, more sophisticated force sensing technology come to life in our everyday world? He was certainly at the ready with a confident answer. “Instead of having a button with an inset, there will simply be an engraving on the device. Underneath that is our thin film, the sensor, which will be able to feel pressure through the outer surface of a device with a range of sensitivity down to a few millimeters,” he details. This has the added advantage making things watertight, and also allows displays get larger. “We’re looking forward to some serious revolutions in how buttons are used in electronics today,” Lougheed insists.
Another unique application for force sensing is with ATM machines. With Exar’s force sensing solutions, users could set a password with not only numbers, but with the degree of force used to enter the numbers. For example, if the password is “1234,” the user could just to push “1” hard, “2” light, “3” hard, and “4” light—adding a whole other layer of security to highly sensitive applications.
Further, though, just how sensitive is Exar’s force sensing solutions at present, and how is it challenging the capabilities of the field? Lougheed made it easy to understand, describing how “normal systems today might need as much as 400g before they feel any pressure. But we’ve been developing systems that are advanced enough to sense pressure as low as 50g.” This, James adds, is much less than almost any of today’s force-sensitive consumer devices are made to sense. Likewise, Exar’s designs allow for an incomparable level of touch-range specificity. “Part of what our unique analog front-end does is calibrate out the ‘noise,’ or the DC offset voltage, essentially cancelling out the generalized pressure being applied in favor of a much more exact sensitivity,” Lougheed elucidates.
While there’s certainly a lot of exciting potential in view for this kind of force sensing technology, Lougheed relates that it will take a bit more testing to get its industry reputation to the level of other common solutions. “There’s a good amount of reliability data that’s being collected, but this is still very new technology relatively speaking. There’s lots more to look at in terms of use-hours, but all the reliability tests that have been done have been very promising,” he says. Still, Lougheed relates with some tangible excitement that the company has already been a part of a design process that will see the first completely buttonless phone being released soon. With that obvious expertise, the innovative lead in the industry, and the honest eagerness to be a part of the next redefining generation of touch-sensitive devices, Exar has clearly got more than what they need on hand to help customers of all kinds to get involved.