Just Hit Print: A New Way to Obtain Rapid Prototyped Capacitive Touch Keypads

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By digitally printing conductive ink to film, a Florida company bypasses the traditional silk screening method to produce film keypads with lightning speed

By Mark Shortt
Editorial Director
Design-2-Part Magazine

As smart phones and tablets find their way into the hands of more and more consumers, capacitive touch technology continues to gain traction over traditional mechanical membrane switch interfaces by enabling the design of a flexible, intuitive, and modern looking interface. One company at the center of this trend is Blue Sparq, Inc., a high-speed product development company in Cape Coral, Florida, that provides a rapid prototype capacitive touch keypad service through its RapidKeypads.com division. The division recently introduced a unique custom USB Touch Keypad design service, through which individual keys on a keypad are mapped to standard keys on a keyboard or other input devices.

"Our capacitive touch technology can sense through any non-conductive material," says Blue Sparq President Jameel Ahed. "Just like the iPhone touchscreen: You touch the top of the glass, it's actually sensing through the glass and seeing where your finger is. It's very similar to what we do here. They make a touch screen; we make touch buttons."

Ahed started Blue Sparq as a product development company in 2008, intending to specialize in work for the aerospace, medical, consumer and industrial product design markets. As the company got going, he started noticing a pattern among the people that were approaching them with product ideas. "They all wanted to take advantage of this new capacitive touch interface for their product," said Ahed. "So instead of having mechanical switches and membrane switch keypads, they wanted some kind of touch keypad."

While working on its customers' product development projects, Blue Sparq began to face its own challenges. When Ahed asked some of the vendors that make graphic overlays and keypads to do some work for them, they responded with long lead times. "For us, a 4-to-7 week lead time is just not doable," he lamented. "The customer is asking us, from start to finish, for a 3-to-4-week lead time on the whole product. So if we had a keypad that needed 7 weeks to make, then there's just no way that we could hit those deadlines.

"Having these vendors tell us that they couldn't make keypads fast enough gave me enough of a fire to say, "We're going to figure out a way to make a rapid prototype keypad service," said Ahed, who saw the need for such a service as stretching beyond Blue Sparq's own internal customers. "There's got to be a ton of people out there that need a keypad a lot faster than 4 to 7 weeks," he recalled thinking. "That's really how RapidKeypads.com was born."

It's this new division, RapidKeypads.com, that separates Blue Sparq from other product development companies and makes the company special, according to Ahed. "It's been the niche that brings us bigger projects," he says.

"For instance, we have aerospace customers that contact us looking for a keypad," he explains. "When they learn that these capacitive touch keypads require electronics to operate properly, they give us more of the project to do because we can add more functionalitymore product functionality--into the same electronics that are used to read or do the button scans. Now they're getting a lot more bang for the buck. They came looking for a keypad, and they leave with not only a keypad, but in some cases, the entire control electronics for their product."

Blue Sparq has filed more than a dozen patent applications, many of them having to do with the rapid prototyping technologies that it has created through RapidKeypads.com. One is for a digital conductive ink printer that enables the company to produce film keypads with what Ahed calls "lightning fast speed" by bypassing the traditional silk screening method.

"We have the ability to digitally print conductive material or conductive ink to film," says Ahed. "So if you draw a simple circuit, or, in our case, a capacitive touchpad sensor circuit, we can hit print, and it produces it right there, in front of us. Instead of going through the traditional silk screen process, which is what's been used forever to make these conductive circuits, now we can digitally print them. And that's a huge plus in speed."

RapidKeypads.com advertises keypads in 5 days or less. "Not only do we supply the conductive film keypad portion, but we supply the electronics for that in the same time frame," says Ahed.

Before they could actually print a keypad that fast, a couple of hurdles needed to be overcome. One was finding a way to replace the traditional silk screen printing method--which, by its nature, requires a lot of time--with a faster method. "Those screens have to be made, those machines have to be set up," says Ahed. "And that's really why these vendors out there, they all say 4 to 6 weeks, or 4 to 7 weeks, because it's a very time consuming job.

RapidKeypads.com ended up replacing the silver ink conductive layer--traditionally printed using a silk screen process--with a high-speed digital printing method. "We can print that part out instantly," says Ahed. "As fast as you can hit print on your Microsoft Word document, and that page comes out of your printer, that's really what's happening here."

The second hurdle, according to Ahed, was to make a universal capacitive touch driver integrated circuit (IC) that could be easily configured by a design engineer without any previous experience in capacitive touch design. Not an easy task, considering that each capacitive touch keypad requires a custom set of electronics. The company's capacitive touch technology can sense through any non-conductive material, and the electronics for each keypad button have to be specifically tuned.

"No two capacitive touch keypads are alike," says Ahed. "For every button that we draw, let's say we draw out a rectangle, and we connect that rectangle to the circuit board with a trace. That rectangle of whatever X, Y dimension has to be tuned specifically for the fascia that it's sensing through. Every time we make a keypad, whether it's for a kiosk, or for a handheld medical device, those buttons have to be tuned. It's basically a custom set of electronics for that product.

"Custom electronics and custom software take much more than 4 to 6 weeks, generally," he continued." So that hurdle was, if we can print the keypad so fast, we better have a solution for electronics that fast. And that's how we came up with what is now known as Fast Touch^TM, our Fast Touch electronics system, which allows us to tune these buttons really quickly."

The Fast Touch™ electronics system consists of hardware and software configuration tools that help the engineers at RapidKeypads.com tune the buttons to different overlay fascias, choose between various noise rejection algorithms, and select the appropriate communication protocol, whether that's USB-HID, SPI, 12C, or UART. RapidKeypads.com supplies the engineer with a complete capacitive touch interface that includes a custom capacitive touch keypad, along with the necessary touch switch driver electronics. The Fast Touch system is complete; the engineer doesn't have to write a single line of code.

"If we're making a USB keypad, which has become very popular now, we can map your custom buttons," says Ahed. "We can map them to keys on a keyboard. So if it's -'Volume Up,' we map it to the -'Volume Up' button; if it's -'Play,' we map it to the -'Play' button, and you just plug it in. You don't have to write any software; you don't have to do anything. It acts just like a computer keyboard."

All of these things, Ahed says, have sped up the development time for customers dramatically. "What used to take months to develop is now just a matter of days, a matter of weeks, and that's it."

RapidKeypads.com is well-equipped with machines--including a Fused Deposition Modeling (FDM) machine, a high-powered laser cutter, and digital printers--that help them make customers' products quickly. "As a product development house, we're comfortable not only doing electronic design and software design; we're comfortable with mechanical design as well," says Ahed. "So when somebody has us do a product, nine times out of ten, they'll have an enclosure that needs to be made, or some mechanical parts that need to be made. We have SolidWorks here, and we'll model up their parts, and print them out using the FDM machine.

"The fact that we can sense through non-conductive materials, and our buttons can be placed inside of enclosures and things, gives a couple of huge advantages to engineers that normally aren't in the loop of deciding or choosing a keypad or switch technology," Ahed continues. "A lot of the industrial designers--the engineers that are responsible for making things look good--need to know about this technology because it allows you to put buttons on the inside of curved surfaces. A mechanical switch has hard edges and won't work well on a round or a radiused corner. Whereas, with our film, you can peel and stick it to the inside of that enclosure and now that edge or that corner is touch-sensitive."

Another benefit, Ahed says, is that because the technology is sub-surface, keeping it clean becomes very easy, an important advantage for medical products. Clean, water-proof, and explosion-proof enclosures can be easily obtained because it's no longer necessary to breach or drill the enclosure to attach the buttons. "You can imagine just an airtight, water-proof enclosure," says Ahed. You just stick all your buttons and controls on the inside of the box, and then you just simply print some kind of graphic decal and stick it on the outside of the box so that your customer knows where to put his finger, and now you can control that product through that box without having any kind of holes, any kind of slots cut in for the mechanical stuff. It becomes truly sealed."

The company has customers in multiple sectors, including medical, aerospace, industrial, and consumer products. "We've done a lot of aerospace," Ahed said. "We're doing controls for private jets--things as simple as coffee makers and ovens that go into private jets. We've done a lot of industrial work, including a really nice job on ultrasonic cleaning equipment. We've also done several consumer products, including a treadmill."

One of the company's most satisfying projects involved making a custom medical device that, by detecting the presence of a finger, would enable an ALS patient to call for help from his hospital bed. The patient had lost his ability to speak and didn't have the strength to press a button or bell. His disease had caused paralysis throughout his body, leaving him with extremely limited use of the index finger on his right hand.

In speaking with the head nurse of the team that was taking care of the patient, Ahed asked her what the patient was still able to do. "She said he can slightly move his finger side to side. And I said, -'Good. That's all he needs to be able to do to call for help.'"

RapidKeypads.com used its ability to digitally print capacitive touch switches and its Fast Touch electronics to detect the presence of a finger and provide audio feedback. The system was packaged inside an off-the-shelf plastic enclosure.

"I used all of the rapid prototyping capability we had," Ahed recalls. "So I digitally printed a single-button conductive film and plugged that single-button conductive film into an inline board, which is nothing more than a small PC board with a small IC on it that has the capability of scanning and reading that one button that's hanging out there. The board that I used actually had the ability to read 16 buttons, but he just needed one. It also had an audio IC onboard.

"I sent the nurse a variety of sound effects and asked her to play it for him. And I said, -'Have him choose the sound that he likes the best.' He ended up choosing a doorbell sound, and that's all I needed. I loaded that file into the IC and mapped the button press to play that sound. There wasn't a single line of code that needed to be written."

All of this was done in just a matter of hours. Ahed later received an email from the patient's nurse, thanking him for the medical device and saying "It works exactly as you said it would. The patient used it for almost an hour straight, smiling the entire time. Great job! He no longer has to struggle to be heard."

A video of the device can be seen at http://youtu.be/lvK3CskEoJU.