Design Engineering

Eight-legged cell phone “airbag” designed to save expensive digital devices

Devin Jones   

Quality crowdfunding Germany iPhone

The spring-loaded design pops open when sensing acceleration and folds back into a slim compartment on the back of your device.


The nightmare of a cell phone slipping through scrambling fingers is universal. Reflexively, we wrap our ~$1,000 lifelines in thin coats of plastic, weighing aesthetic design versus structural safety. For many, those “safety measures” lead to an Apple Genius reporting on the extent of their mistake.

But what if we didn’t have to worry about lurching erratically to catch our phones? What if the fear morphed into a sense of security knowing your device—packed with more processing power than the Apollo 11 spacecraft—could land safely on concrete like nothing happened?

Cue Philip Frenzel and Peter Mayer, the duo who’ve created ADcase – essentially an airbag for your cell phone.


Wrapped in a sleek design, the ADcase seems pretty inconspicuous at first glance – a standard molded case. But when an accident inevitable occurs, eight spider-like legs spring out, inches before the phone hits the floor, to act as a cushion.

With AD standing for “active damping,” Frenzel’s design employs 30mm, spring-loaded legs that fold into a slim casing attached to the back of the phone. Accelerometers, housed in the casing, sense the standard acceleration of gravity (9.81 m/s^2). As the phone goes into freefall, the sensors trigger the legs to deploy.

According to Mayer, this not only saves the phone but also prevents the ADcase from popping open in your pocket.

“There’s other sensors in the case that recognize your hand and leg if it’s in your pocket,” Mayer says. “Or, if it’s your bag, it’ll recognize objects and understand there’s no need to deploy here.”

Frenzel came up with the idea after a routine incident left his phone cracked and damaged after walking home from engineering classes at Aalen University in Germany. After picking up his iPhone and lamenting the loss of a pristine screen, he asked the obvious question: Now what?

“Of course, I drop my phone in its case and the screen shatters. So I think, there has to be a solution here. It just took me two years to really figure out what that was,” Frenzel said.

At first, the duo prototyped various types of foam cases that would act as a damper for when a device fell, but ran into trouble when it came to the ergonomics. The design philosophy, according to Frenzel, was that ADcase needed to be both comfortable to carry and use, but practical in its desired application. Additionally, they had to figure out how to get the loaded springs to only pop out, but curve outward to provide protection.

Related: U of T engineers place first at international competition with sustainable yacht design.

The actual design of the eight legs mimic a pocket knife: slim and ergonomic. Additionally, the spring-loaded legs are made from a combination of metal and plastic that fit neatly back into their slots.

The ADcase is slated to launch its crowd funding campaign in the next 4-6 weeks. Currently the duo is only working with iPhone models 6 through 10 (including any Iphone+) since the design specifications on the newer generations are very similar.


However, Mayer does note that, if they met their funding goal of €500,000, they would be working on bringing ADcase to other device platforms. The current plan is to market the ADcase at €50 or $77 Canadian.

“We need to talk with vendors and get some prices to help set the funding goal and because Apple shares a very similar design specs in terms of placement of camera and width the bodies, that’s what we’re working on right now.”

When asked if the ADcases would be available by Christmas, both Fenzler and Mayer noted that this was the plan. 


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