BIDET
portable, accessible hygeine
"Do I skip lunch today or ask a total stranger to help me use the bathroom?"
This is the sort of real and painful question that our client Sarah asks herself regularly. Her cerebral palsy significantly limits her mobility and dexterity, and she uses a power wheelchair to get around. An ADA coordinator, she is all too familiar with the shortcomings of public restrooms for users like herself. Being able to relieve and clean ourselves independently when we're out and about is something the vast majority of us take for granted, but for Sarah it's essentially impossible. With toilet paper not an option due to her mobility restrictions, she either has to bring a Personal Care Assistant (PCA) into the bathroom with her, or else make a difficult sacrifice: no food and drink, or no outing.
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At home, Sarah uses her bidet to clean herself, but this isn't an option in public. During my senior Assistive Design class—which was perhaps the most eye-opening course in my undergraduate experience—my team worked with Sarah to engineer a solution to this chronic problem.
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The task: Design a robust, portable, and reliable bidet to grant bathroom independence to people with limited mobility.
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The timeline: Spring semester 2023 (roughly three months)
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Sarah had previously worked with an MIT Hackathon team on this project, who built the so-called "Bom-Bidet" in 48 hours. That team did a lot of things very well, and they put build instructions online in an effort to make their work more easily reproducible. However, as is inevitable on such a short timeline, there were several mechanical and electrical issues that prevented their prototype from surviving more than a week or so. The goal for this semester was to use our more generous timeline to deliver a correspondingly more polished product.
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Sarah was clear from our very first communication that our work would be about answering as many questions as possible, as well as posing new questions for future teams. Since we were the first team to spend a semester on this project, she held no expectation that we would completely solve the problem. This realistic transparency was refreshing and reassuring, shifting the focus away from our conception of the final product and towards the series of actionable steps required to get there.
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I was in charge of designing and building the physical device while my teammates worked on client outreach and other project deliverables. Commercial portable bidets, which are most commonly simple squeeze bottles, are unusable for Sarah, either because of insufficient reach, insufficient water pressure, insufficient water volume, the prohibitive necessity to pump/squeeze the water manually, or a combination of these issues. As such, we determined quickly that a powered solution was essential. The Bom-Bidet team thought of this too, but their pump was on the stationary reservoir while the button to turn it on and off was at the end of the moveable handle. This meant their electrical wires were quite long and had to be wrapped around the water hose connecting the handle to the reservoir, putting constantly varying strain on the electrical connections and causing them to fail quite quickly.
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To get around this, I decided the on/off control would have to be purely mechanical. Sarah also said that the momentary push button required too much strength to hold down, and that a toggling option would suit her needs better. However, it was very difficult to find such a component, so for the first prototype I focused on the bare minimum pump circuit just to get a feel for the problem.
It looks rough, and it is, but this prototype was extremely quick to put together and gave me plenty of insight for the next iteration. At this stage, that's all I'm looking for.
Right away it was obvious the pump was extremely underpowered for the task. While blocking some holes on the cheap plastic nozzle did result in a higher outlet velocity and thus better cleaning power for the available pressure, it was still nowhere near enough.
In terms of the general architecture, however, it's headed in the right direction. The 1L reservoir is a decent volume while not being too unwieldy, and the air inlet hole prevents collapse under vacuum.
For the next iteration, I got a much stronger pump and a rechargeable 9V battery, as well as a buck converter to step up the battery output to the 12V and 3A for which the pump is rated. I also invested in a waterproof power button, planning ahead for the eventual enclosure that will house all the electronics.
While certainly an improvement, the water pressure was still lacking, and I suspected that the current limiting of the smart battery was resulting in insufficient power passing through the buck converter to the pump. For the final iteration of the electronics, I wired two of the batteries in parallel to double the max current.
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I then housed all the electronics in an IP68 diecast aluminum box. I had to machine several holes in it to accept the pump, power button, and battery charging ports, as well as mounts for the buck converter, nozzle rest, and reservoir holder. When assembling the box, I sealed these holes with O-rings to keep water out. The battery ports couldn't be easily sealed, so I made a magnetic cover for them that snaps on to protect against splashes while being easily removable for charging. I also finally found a bidet nozzle with a purely mechanical toggle control, and it has plenty of reach for Sarah.
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I designed and 3D printed the reservoir holder to snugly accept a square plastic jar. The shape is easy for Sarah to grab, and the wide lid makes filling much more straightforward.
At the end of the semester, we got to visit Sarah and show her the bidet. She was thrilled overall and pleasantly surprised by the water pressure, which easily and thoroughly cleaned peanut butter off her hand. She had some comments on the usability, suggesting more direct labeling to indicate the functionality of each component. Since she lives far from campus, we weren't able to meet up earlier to take measurements of her wheelchair, so we decided that this bidet might stay at home for the summer during early testing. Perhaps the next group to pick up this project will have more access to the chair and can tackle the attachment problem more thoroughly. As it stands, however, this was an extremely rewarding project and one of my most polished builds to date. Below is the final glamour shot as well as the function structure diagram of the bidet.
