DIY printing custom touch-sensitive displays

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The PrintScreen lets anyone print their own custom displays.

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In recent years, the industry has advanced by leaps and bounds when it comes to flexible touchscreens, albeit reproducing this technology for DIY projects has been a daunting task. Have you ever wanted to devise an interactive prototype with a display, like a smart plant that can reveal incoming calls or messages? Or, how about a touch-enabled greeting card for a loved one that could depict self-created symbols? Or, perhaps a postcard that illuminates in color when triggered? Despite countless innovative ideas, affordable displays for initial mockups can be quite bulky and only come in a few sizes.

That may soon all change thanks to a group of researchers from Germany’s Saarland University who have developed a technique that could allow anyone to literally print their own custom displays, including touchscreens. The aptly-named PrintScreen has been designed to facilitate the next-generation of digital fabrication for customized flexible displays using thin-film electroluminescence (TFEL). Through the approach, an ordinary inkjet printer will pave the way for inexpensive yet rapid production of highly-customizable screens in low volume, ranging from a simple lab environment, a print shop or even at home. (It’s almost like temporary tattooing meets in-home graphic t-shirt making meets 3D printing.) The possibilities for endless as these TFEL displays can be integrated into almost every object in daily life, whether that’s affixed to paper objects, furniture, decorative accessories, bags or garments.

“We show how to print ultra-thin (120um) segmented and passive matrix displays in greyscale or multi-color on a variety of deformable and rigid substrate materials, including PET film, office paper, leather, metal, stone, and wood. The displays can have custom, unconventional 2D shapes and can be bent, rolled and folded to create 3D shapes. We contribute a systematic overview of graphical display primitives for customized displays and show how to integrate them with static print and printed electronics. Furthermore, we contribute a sensing framework, which leverages the display itself for touch sensing. To demonstrate the wide applicability of PrintScreen, we present application examples from ubiquitous, mobile and wearable computing,” the team of Simon Olberding, Michael Wessely and Jürgen Steimle writes.

How it works is relatively simple. Using a regular inkjet printer equipped with some conductive ink, Makers and designers alike can produce DIY displays from a digital template of a desired size and shape with programs such as Microsoft Word or PowerPoint and an editor like Adobe Illustrator. Making use of one of the two methods the researchers have been presenting, the template can now be printed out in about two to four hours, depending on the exact procedure, size and colors. Nevertheless, these results will be high-res displays that are just 1/10mm thick. To cover an entire standard printer page currently costs €20 ($21.69), with the most expensive part being the special ink that is required.

In order to light up a display segment, the team has crafted a controller that is tasked with applying a high-voltage, low-current AC signal between the upper and lower electrode layers. The luminance of a display segment or pixel is then controlled using pulse-width modulation (PWM), a standard method for controlling the luminance of LEDs. For mobile applications, their prototypical controller utilized a small driver IC that generates the high-voltage AC signal from a 1.0-7.0V DC power source. If a higher luminance is required, a stronger driver IC with a slightly bigger footprint can be implemented. Meanwhile, an ATmega2560 MCU triggers the optocouplers for multiplexing the high-voltage signal between display pins.

“The TFEL-specific ghosting effect in passive matrix displays can be significantly reduced by using a slightly modified controller design, thus further increasing the contrast of the matrix,” the team reveals.

“So far, nothing like this has been possible,” Olberding adds. “Displays were produced for the masses, never for one individual user.”

Printing a regular high-res display could be just the beginning, as the researchers hope PrintScreen can be used with other materials like leather, metal, stone, and wood in the future. Interested in learning more? The researchers will be exhibiting their solution at Cebit in Hanover, Germany this month. Meanwhile, you can read their entire paper here.