The walls around us everywhere don’t merit much thought, usually. But our run-of-the-mill walls will no longer serve merely as a room divider, not if a team of researchers from Carnegie Mellon University (CMU) and Disney Research has anything to do with it.

The researchers have figured out a way to convert ordinary walls into smart walls capable of sensing human touch and detecting gestures or even the use of appliances.

What will smart walls bring? The researchers believe the system could be used in many ways, including controlling video games with gestures, adjusting light levels when a TV is turned on, or alerting a user who’s in another location when a laundry machine or electric kettle is turned off.

Their new sensing method, called Wall++, makes the transformation possible with just a few applications of conductive paint and some electronics and, at about $20 per square meter, is relatively inexpensive to boot.

The research is led by Yang Zhang, a doctoral student in CMU’s Human-Computer Interaction Institute (HCII), who is scheduled to present a research paper on the system at CHI 2018, the Conference on Human Factors in Computing Systems, April 21-26 in Montreal, Canada.

Why walls?

“Walls are usually the largest surface area in a room, yet we don’t make much use of them other than to separate spaces, and perhaps hold up pictures and shelves,” Chris Harrison, an assistant professor in CMU’s HCII, said in a statement.

“As the internet of things and ubiquitous computing become reality, it is tempting to think that walls can become active parts of our living and work environments.”

While sensing solutions exist, the researchers sought to develop one that is both affordable and unintrusive.

“There are many sensing solutions out there to enhance a room with sensing and computation, but they can be expensive and intrusive,” said Zhang.

“On the other hand, walls are already everywhere. They typify our living environment. So, we wondered at the beginning of this project – can we make walls smart so they can track users as well as appliance use?”

With those requirements in mind, they set out to find a solution that fits the bill.

“We went through a multi-phase experiment where we investigated paints, backing material, application methods, topcoats, and patterning,” said Zhang.

“We optimized for cost, conductivity, consistency, and efficiency, and eventually chose the method we used.”

The method

The team’s method involves the use of conductive paint to create electrodes on a wall, which makes it possible for the wall to function as a giant touchpad that senses human touch as well as an electromagnetic sensor that detects and tracks electrical devices and appliances.

To keep the cost low, the researchers used a water-based paint containing nickel.

They also made sure that the process would be easy to use.

As their first step, they used painter’s tape to create a cross-hatched pattern on a wall resembling a grid of diamonds, which they found to be the most effective pattern.

“Through a series of experiments and simulations with different electrode patterns, we found this one yields the longest sensing range,” said Zhang.

“It also densely covers the wall surface, which makes it less likely to miss user touches.”

Next, they applied two coats of conductive paint using a roller.

Then they removed the painter’s tape and connected the electrodes.

Their last step was to paint the wall with a top coat of standard latex paint, which serves two purposes: to make it last and and keep the electrodes hidden.

Once the electrodes are connected, the wall becomes both “capacitive sensing” and “electromagnetic sensing.”

The former means that the wall functions like a typical touchpad, so a user’s touch would alter the wall’s electrostatic field at that point.

The latter means that the electrodes can detect the unique electromagnetic signatures of electrical or electronic devices that are in use and identify the devices and their locations.

The wall’s electromagnetic sensing capability is not limited just to devices, according to Zhang. It can also track the location of a person wearing a device with an electromagnetic signature.

What’s next?

The researchers plan on optimizing Wall++ for energy consumption, Zhang said. Currently, the system is estimated to consume about as much power as a standard touch screen.

They also plan on finding a way to reduce the cost of the system even more.

“Though we lowered the cost by two orders of magnitude compared with existing touch screen technologies, it still requires more effort to further lower the cost to match papers (i.e., ~ 1 cent per sheet),” said Zhang.

“Pulp Nonfiction is a research experiment that shows the potential of single-use digital papers.”

Zhang added that the team has “still a lot of work to do to make it commercially available, which might take 2-3 years.”

The research team also included Scott Hudson, a professor in CMU’s HCII, and two researchers from Disney Research — Alanson Sample and Chouchang (Jack) Yang.