How cool is that!

Posted on 01/07/2017 by IED

Many wheelchair users experience discomfort from overheating, due to long stints of sitting in their chairs. There has not been an appropriate solution – until now, it seems

Glasgow-based start-up Staels Design was founded just over a year ago by Corien Staels after she first became aware of the cooling problems experienced by wheelchair users. Crucially, what she discovered was that many users had to cool themselves in dramatic and unforgiving ways – having to strap ice packs to their bodies or spray themselves with water hoses, post-exercise.

Those with a Spinal Cord Injury (SCI) are particularly affected, because their bodies can no longer communicate with their brains to say they are overheating and need to start sweating. This can easily lead to heatstroke and hyperthermia.

“As time went on, more and more wheelchair users resonated with the overheating issue,” says Staels. Her immediate thinking was: “This is the 21st century... It’s time for a change!” And while engaged on resolving this issue, she also decided that function and looks were both important aspects of what she was setting out to achieve. “You don't buy ugly clothes just because they are functional, right? So why do so many wheelchair-related products lack sleek and stylish design?”

FUNCTION, COMFORT, STYLE

Enter the WheelAir, a battery-powered, ergonomically designed backrest cushion that cools the user by gently blowing air onto their backs. It combines function with comfort, without compromising on style. The cushion currently fits all manual active lightweight wheelchairs and the company has big aspirations eventually to provide cooling solutions for all wheelchairs, both power and manual.

The WheelAir, officially launched on 3 June, has come a long way since its first prototype two years ago. Early prototypes indicated that blowing air through a flexible hose with intermittent perforations was the most effective method. However, as they were using a high flow, low pressure air source, the airflow exiting at the far end of the hose was significantly less than at the inlet end. The design scope had to be widened to consider three other concepts:

  • A low flow, high pressure (LFHP) air source (a compressor) with restricted air path and valve-like perforations
  • Thermoelectric modules (Peltier modules)
  • A high flow, low pressure (HFLP) air source (a blower) with unrestricted air path.

The team then developed some basic prototyping systems for each of these methods to evaluate their effectiveness qualitatively. With the assistance of the design engineering team at STEP 3D, a product development and 3D printing studio also based in Glasgow, they created basic prototypes for each method, starting with the thermoelectric modules. They used combinations of 2 to 6 Peltier modules, coupled to a flexible graphite heat spreader to absorb as much body heat as possible. Unfortunately, there was no way of integrating the Peltier modules into the cushion in a way that was comfortable and unnoticeable to the user, and the method had to be abandoned.

Next, they explored using a low flow, high pressure system (compressor), but were dissatisfied with the inefficacy of the cooling. Furthermore, the compressors were audible and produced vibrations that would prove irritating to the user.

The third concept of an integration of a high flow, low pressure air source (blower fans) with an unrestricted air flow path through the cushion seemed like a less efficient method than the compressor-based system. Nevertheless, they mocked up a foam cushion with an unrestricted air flow path and 3D printed some components to connect some DC blower fans to the air flow path and it worked – in fact, it worked too well! Clearly, the real WheelAir design challenges lay in the embodiment and implementation of the cooling system in a way that was effective, discreet and unobtrusive. From the outset, the team knew that the main technical challenges were going to include:

  • Driving a suitable airflow source
  • Distributing the moving cool air across the backrest
  • Mounting the airflow system to the cushion itself
  • Making the product easy to use, install and remove
  • Ensuring that, as a retrofit product, the apparatus would be compatible with as many different wheelchairs as possible.

Initially, they tried using PWM to drive the fans at different speeds, but the noise produced by the PWM hum was unacceptable. Their electronics engineer then suggested using an adjustable voltage power supply to provide constant voltage at the varying levels. They used qualitative evaluation techniques, asking different users to try a variety of cooling strengths, in order to home in on the optimal power range. What they didn’t want to do is provide a baltic blast of freezing air, but a more subtle, gradual cooling sensation that wasn’t obvious or uncomfortable to the user.

The next step was to create an air flow path that allowed even distribution of cool air across the full height and width of the backrest. Pressure mapping research made it obvious that the symmetry of the human body typically created two areas of higher pressure: to the left and right of the spine. With this in mind, they set to work on developing a cushion embodiment with two channels that would distribute the air from the two blower fans.

The foam cushion itself is a custom-designed lamination of different densities of high quality viscoelastic foam. The foam cushion was designed in such a way as to provide ergonomic support, moisture wicking and support for the cooling system, while minimising bulk, folding easily and conforming to economic manufacturing process design rules. Lastly, the team had to design a fabric cover that would enhance the distribution of airflow, while being easy to clean and stylish enough to fit the brand’s purpose. They therefore opted for a high quality Polyester 3D spacer mesh treated with an antibacterial finish, in combination with PU faux leather.

UP TO THE TEST

While a fairly typical usage of prototypes for design validation along the product design process was employed, the team recognised that the WheelAir would need an extensive amount of testing. Jay Anderson, a multi-disciplined athlete and wheelchair user, reported back: “This is the first time I’ve been in the park in the sun without overheating in twenty years. And not only is it adding so much comfort, it is actually attractive!” And there was praise in the same vein from Michael Kerr, the double Paralympian wheelchair rugby player and former captain. “I experience a lot of problems with overheating during games and am glad there is finally going to be an effective solution to this problem, without having to resort to being sprayed with water.”

“The user feedback we received was absolutely invaluable,” says Staels, “as it threw up a number of situations that we hadn’t considered (eg, unusual wheelchair-folding mechanisms, issues with the remote control location and the general robustness of the product). These problems were addressed and design changes implemented in less than two weeks.” Overall, the team was able to progress from the first prototype to the final stage in nine months of starting the new experiments, she confirms.

The project is in its final pre-manufacturing stage and seeking £30,000 in crowd-funding, against a target date of October this year to start manufacturing, with shipping to commence a month later. See http://kck.st/2qDHG21

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