Creating Kiti Kasha: A Postural Support Seat for Children

Testing the comfort and effectiveness of the Kiti Kasha prototype

Even for people with total control over their muscles, sitting in a healthy posture can be a challenge. For some people with muscular disabilities, this challenge is magnified to become a genuine danger. Sitting in a healthy way may feel easy, even automatic, but in fact, learning the control that lets us do this is a skill we develop over a long time when we are young. 

For many children with a deficiency in muscular control, like those with cerebral palsy or hydrocephalus, the postures their bodies naturally fall into can be dangerous. Our bones will fuse and our muscles will permanently shorten if left in a position long enough, limiting our range of motion—sometimes to painful ranges—for the rest of our lives. Preventing a child from getting stuck in an unhealthy posture (for example with their spine or neck curved), can help prevent other medical complications later on and provide the child with a better chance of gaining more mobility later in life through physical therapy.

As I learned when I came to Arusha to volunteer at Kyaro this summer, in low-income countries like Tanzania, disabilities like these are much more common than in the United States because of higher instances of perinatal complications, infectious disease, and malnutrition. 

My teammate—Caroline, also an engineering student from Olin College of Engineering in Massachusetts—and I were tasked with designing a postural support seat during our three-month volunteering stint. The users of such a device are young children who are too small for a wheelchair (generally under three years old) and who need support to help them sit in a safe position. 

To start gathering information, we talked to three pediatric occupational therapists from around Tanzania, and the CEO of Kyaro, who often interfaces with them and their families to provide assistive devices. We learned about the needs of the children, the challenges faced by their parents and therapists, and the major issues with existing devices.

After our initial research, we synthesized three major takeaways that drove our design.

• First, the children’s caregivers are often on the move, visiting relatives, markets, workplaces, daycares, church, and many other places, generally without a personal car. The most common forms of transport are walking, taking a motorcycle, or using daladalas (the minivans that work as a bus system within most Tanzanian cities). In Tanzania, children of this age are usually carried on their mothers’ backs in wraps called kangas, which is a great option for most kids but can be dangerous if they have a disability and end up in an unhealthy position. Based on this, we wanted to prioritize the transportability of our device. That would allow children to be in healthy positions while being carried but also to be able to use the seat outside their homes, because it can come with them to the different places they spend time in. To achieve this, we optimized its weight and bulkiness, using wood and fabric rather than metal, as well as having a method for easily carrying it, modeled after backpacks.

Different ways parents may carry children in kangas. Image credits: left - wrap your baby; right - njokis fashion

An early gallery sketch of one concept.

• Second, therapists complained that most existing postural support seats are bulky because they have a full self-standing frame that sits on the ground like a high chair. We wanted to make our device use a normal chair as its frame so that it could be lighter, smaller, and less expensive. We particularly focused on making it compatible with the plastic Jambo chairs that seem ubiquitous across the country. That means you can set it up basically anywhere, because if you carry it with you, then you can set it up in the new location as long as there is a chair around (a safe bet in just about any Tanzanian home or business).

Another early sketch of the concept of using a plastic chair

• Third, children in this age group span a wide range of sizes and have a notorious habit of growing. We wanted our product to come in a single size, rather than being made custom for each child, but continue to accommodate them as they grow. Thus, our support seat focuses on adjustability, allowing it to continue to fit a child for several years.

An early concept for a mechanism for adjustability using foam inserts

We took inspiration from slings, kangas, and backpack-style child carriers, but we made ours more rigid so it can provide postural support. We also opted early on to have two separate parts to our device: the base and the seat. The base stays in the user’s home, so it doesn’t need to be as lightweight. It keeps the child securely in place and attached to the base chair. The seat has all the necessary postural support for the child, and it is the part that can be used as a backpack and brought along.

Another interesting consideration was that there’s a range of supports that a child might need—for example, lateral armpit supports, knee separators, or chest harnesses—but not every child will need every support. We learned a lot more about disability, posture, anatomy, and physical therapy than we expected, and eventually, we settled on a set of supports that would accommodate most people’s needs. It was difficult to include all these supports without the device becoming complex and difficult to use, so we had to simplify them as much as we could.

Gallery sketch showing the beginnings of the concept that became our first prototype.

One of our unexpected challenges was just getting the materials for our prototypes. We found that when we wanted to research available materials, we couldn’t just use the Internet. We had to visit each store in town (which were often not on Google Maps) and ask them in person if they had what we needed. I’ve become a regular at no fewer than fifteen hardware, fabric, and carpentry stores in Arusha. It was pretty common for us to want a specific part–for example, wing nuts–and go to store after store in search of them, asking at each store where we should go next. Sometimes, we had to redesign our device because we couldn’t find a part. Patience and flexibility thus became keys to our process.

Me and Caroline working on a prototype

After we had secured our parts and completed each prototype, we moved on to one of the best parts of this process. To test our device in person, we went to Sibusiso—another NGO in town which runs 12-week live-in programs for children with disabilities and their caregivers to learn how to care for their conditions—to test and get feedback on our prototypes. This project has increased my interaction with one-year-olds by about a hundredfold, which I have enjoyed immensely. Every time we visited, we found new little considerations we couldn’t have predicted without a child in the seat: the hip strap needs to be longer, and when you pick the backpack up the child tips towards your back, real children are kind of wriggly and tend to grab things. These visits were incredibly helpful, and we got into a rhythm of quick prototyping to make use of them.

Sibusiso physical therapist, Calvin, and American volunteer physical therapist, Evan, assist me with our first prototype. This design didn’t include backpack features and was mainly to test the basic concept. It was designed to meet our key goals of providing adequate postural support, being adjustable for a range of children, and interfacing with a plastic chair.

One of our intermediate prototypes included all the features we wanted but was not yet comfortable and user-friendly.

My other favorite part of this project has been working closely with our workshop staff. They cheerfully helped us make our prototypes and quickly folded us into their friendly community. From them, I have learned a lot of resourcefulness and a little Swahili.

The workshop staff and the volunteers outside the workshop.

One particular technical challenge we ran into came with designing the backpack mechanism. As mechanical engineers, we had little experience designing soft things and it’s incredibly hard to test the mechanics of the backpack sling without a child in it. It took several tries to get something that felt stable enough to even lift the child, and several more iterations to get to a comfortable and easy-to-use design. We started with the most simple implementation we could think of: attaching backpack straps to the top and bottom of the seat and back. From there, we added features like a swaddle that helps pull the seat into the correct shape when carried, suspension straps to control how far the child’s head is from the carrier’s back, and a waist strap for the caregiver.

This is a progression of the backpack straps. The first prototype, on the top left, could be carried, but it would tip to an angle that made it difficult to carry and uncomfortable for the baby. Adding the red suspension straps and waist belt that are in the second picture helped with positioning and comfort a lot. The third and fourth images show some changes in the way the swaddle and straps interface to make it more comfortable and simpler to use.

After several revisions, we have created a design that simultaneously is pretty similar to the broad idea we started with and very different in all its little details. We hope that once this low-cost and more-transportable postural support seat is available, more children will get access to it, the ease of use will motivate parents to adopt it more, and therapists will see better results with their patients. Now it’s time for it to go out into the world, so we can see how it shapes up and shapes others.