How Automatic Soap Dispensers Tell Us Interesting Things About Human Centred Design — Christopher Roosen (2024)

That everyday thing that just doesn’t work

While out in the world, I often take photos of machines, technology and everyday products that catch my attention. It’s my way of keeping track of things that I found interesting, didn’t work like expected or just didn’t work at all. One interesting little device that I’ve encountered in my travels, now commonplace enough as to be invisible, is the automated soap dispenser.

You might have seen them in a bathroom or hospital, perched up on the wall, ready to spurt soap all over your hands when you make the appropriate gesture under them. Assuming of course, you’re not the one of the one in five people that don’t wash their hands after using the bathroom. Or, maybe you haven’t seen them, because they’ve been ‘artfully’ hidden, but we’ll get to that in a moment. Automated soap dispensers might feel like a thing we’ve had forever, but the first wasn’t patented until the 1990s.

I’ve taken a few photos of these automated soap dispensers over the years. They present an excellent lesson in the presence, or lack of, human centred design. How technology fits into our lives isn’t just about technical challenges. Technical problems are only one part of the story. There’s a liminal space, where how a thing works intersects with how people understand it, and whether it’s available to everyone. Hands clean? Well, sit back and let’s dig into the world of automated soap dispensers.

When was an automatic soap dispenser invented?

The first automatic soap dispenser patent was applied for in 1989 and granted in 1991, to Shiau Guey Chuan. I couldn’t find much about the inventor, but the preamble of the patent is clear enough, as it notes:

“This invention relates to an automatic cleaning-liquid dispensing device, and particularly to a type of cleaning-liquid dispensing device from which the contained cleaning liquid will be automatically fed in given amounts upon sensing the presence of an external object intended for receiving the cleaning liquid therefrom.” (Patent: US4989755A)

Straightforward so far. A device for automatically sensing and dispensing a cleaning liquid. The rationale for the invention comes next:

“Soap or cleaning emulsion or other cleaning articles in public facilities are normally provided for the users to clean their hands. Because of direct contact with a user's hands, necessary when using soap or cleaning liquids, the use of such cleansers in public facilities is not only inconvenient but also facilitates the spread of bacteria. In order to solve this problem, conventional automatic cleaning-liquid dispensing devices are produced for public use.” (US4989755A)

The basic elements of the dispenser are simple: a sensor, a container for the fluid, a motor connected to the sensing circuit and a dispensing mechanism at the end of the motor. Interestingly, the automatic soap dispenser was patented decades after the first patent for liquid soap. Flowing soap was credited to William Shepphard of New York in 1865. He notes in his own application:

“This invention is based on the discovery that by the addition of a comparatively small quantity of common soap to a large quantity of spirits of ammonia or hartshorn is thickened to the consistency of molasses, and a liquid soap is obtained of superior detergent properties.” (Patent: US49561A)

I didn’t conduct an exhaustive audit, but found some early hand-pump dispensers, like this example in 1897, patented by E. S. Palmbla, of Chicago, Illinois. Palmbla’s application specifically mentions ‘heavy liquids,’ like syrups out of casks, so perhaps it isn’t for everyday use.

If I’ve understood Elmer Lee’s mechanism correctly, pressure on the downward-facing spout causes a defined allotment of the liquid soap to dispense through the spring-valve, onto the hands. Withdrawing the hands and the pressure associated with contact would cause the spring to extend, closing the valve.

Following a patent search further continues to expand out dozens of other designs over hundreds of years for soap dispensers. Soap dispensers are a well-stocked category. But what about the automation? For that, we need sensors.

So how does an automated soap dispenser work?

In layman’s terms, a sensor is nothing more than a technological device that can sense the state of the world. Without sensors, machines can’t be automated, because they can’t sense changes in the environment and respond accordingly. Granted, it needs a little bit more than that, but we’ll get to the extra bits in a moment.

Crucially, for our purposes, any automated soap dispenser sensor has to be proximate in time and space to when someone needs it. No good having a sensor out in a hallway, outside a bathroom, to trigger soap dispensing. We have enough trouble getting people to wash their hands as is. If it’s inside the bathroom that hands get dirty, well then that’s where the sensor needs to be.

It’s also no good relying on some sort of distal or far away action. We could use a sensor that responds to the door being opened and run some sort of timer, but that would be arbitrary. Someone may well take more time than we’ve allocated. We’d end up with is soap on the floor, or not enough soap for a line of people at the sink. Sensors have to be near or on our approach to the sink. A few possible sensors types come to mind, each with their own advantages and disadvantages.

‘Emissive’-based radar-like sensors send out some form of energy (microwave, ultrasound or active infrared) and then listen for a return signal indicating an approaching object. Don’t worry, none of these cause harm, as they are low-power and short-range.

‘Light’ sensors send out a beam of light (usually outside our visual spectrum). This beam of light can be constantly received by a sensor. If the beam is interrupted, like when a hand passes through, the sensor is triggered. Finally, ‘Heat’ or passive infrared sensors wait for any peaking heat signature, like the heat coming off a human hand. This energy variation causes the passive sensor to activate.

Along with the sensor, we also need an actuator, motor or some other device that can exert force or pressure. Depending on the type of soap container, the actuator, once triggered by the sensor, dispenses a set amount of soap, without us having to touch anything. Perhaps this begs the question, does it really matter if we touch the soap dispenser? Turns out that soap dispensers may well be a viable mode of disease transmission.

Germ-covered dispensers

We tend to get it, in theory, that every surface that we touch with hands contaminated with viruses and bacteria can serve as a point of transmission. In practice, different surfaces have a different likelihood of germ transmission, based on the surface moisture, surface materials, temperature and other factors. Dry, hot surfaces may reduce the length of time that germs can survive, as can some materials like copper. The soap itself may have antiviral and antibacterial properties.

However, touching surfaces, or splashing them as we wash our hands may leave disease microbes of one kind or another waiting for the next person to come along. Hongsoongnern et. al, in a conference proceeding from the 43rd APIC (Association for Professionals in Infection Control and Epidemiology) Educational Conference notes:

“Previous research has shown increased opportunity of bacterial contamination with an open soap system. In the current study, microbes were found within manual soap dispensers throughout the facility. Additionally, infection rates decreased following the dispenser transition, which may be linked to the switch to a touchless/closed dispenser.” (Hongsoongnern et. al, 2016)

In an exceptional review of touchless environments and hand washing, entitled “Going Touchless is a High-Tech Solution to Hand Hygiene Compliance,” published in Infection Control Today, Charles Gebra, a microbiologist at the University of Arizona, also had concerns about contact surfaces and the benefit of touchless technologies:

“Touchless technology is a good idea, because hard surfaces are significant transfer points for bacteria and viruses,” says Charles Gerba, PhD, a microbiologist at the University of Arizona, Tucson. “Much of what people put down on a surface can be picked up by the next person who comes along, and in an age where people share more spaces and surfaces than ever before, touchless technology can help prevent cross-contamination.” (ICT, 2022)

In a study by Griffith, Malik, Cooper, Looker and Michaels, in 2003, entitled “Environmental surface cleanliness and the potential for contamination during hand-washing,” the researchers tested hundreds of faucet handles, soap dispensers and towel rolls. Their findings were that all three surfaces could present a contamination risk above the ‘clean’ benchmark. Though faucets were the most contaminated there was no statistically significant difference between the disease loads on the three surfaces.

“Similarly, although faucet handles were more likely to provide higher ACCs [aerobic colony counts] and staphylococcal colony counts [both bacterial counts], and be above benchmark values, than soap dispensers or paper-towel dispensers the results were not statistically significant. However, even paper-towel dispenser exits, which carried the lowest levels of ATP or bacteria, could present a contamination risk, if touched, with a mean of 19% being in excess of clean benchmark values for ACC and staphylococci, and more than 80% exceeded desirable ATP levels. Of faucet handles, 5% had some visible surface wetness associated with them, whereas all soap and paper-towel dispensers were visually dry.” (Griffith, p. 95)

So the things we touch in a high-contact environment might be a source of cross-contamination. Which means touchless, automatic technologies are worth getting right. This has probably only become more crucial with Covid-19. Iqbal and Campbell, in a review of the state of the art of touchless technology entitled, “From Luxury to Necessity: Progress of Touchless Interaction Technology,” note of changing social and health risks due to the Covid-19 pandemic

“As a precautionary measure, the need to avoid touching devices & services at public and shared spaces has become necessary to stop the spreading of the disease.” (Iqbal and Campbell, P. 1)

But there’s a catch. For all this automation, this touchless soap dispensing to work, it has to work for everyone, all the time. That is where the story gets even more interesting. After all, automation isn’t a guarantee of a successful outcome. There’s a list of odd interactions stemming from how these automated soap dispensers are built and how we try to use them.

Un-human centred design - the ways automated soap dispensers don’t work for us

The soap dispenser isn’t visible

For an automatic soap dispenser to be useful, it has to be obvious where it is. I once was in an airport and saw a sign for a soap dispenser, but for the life of me, couldn’t figure out where it was.

‘Wait,’ I hear you cry. The sign clearly indicates the dispenser and the very small directional arrow indicates where to go to find it. Some crucial context. It was an airport and I was tired. So I was looking, in a daze for a thing; a spout, object, box, something that communicated ‘soap-is-dispensed here’. The small directional arrow that seems self obvious now passed me by. I waved my hands all over the sign with out obvious outcome.

More context, the soap dispenser was actually under a shelf that ran horizontally, above the sink, along the length of the wall. I guess from an architectural or aesthetic standpoint, this was a very tidy design, but it was difficult to figure out in the heat of the moment.

The category of hidden dispensers should probably include those located up and away from anyone that isn’t a single uniform size, like children and those using mobility aids. Come to think of it, the ‘hidden’ dispenser buried up under the sink rim might well be quite difficult to reach for anyone with a different system of mobility than a standard adult male, which is often what design teams fixate on.

The soap dispenser doesn’t communicate its use

An automated system has to communicate its use. Put another way, it has to communicate its affordances. Curious what an affordance is? Than you can read more about the affordances of Q-tips. But do that later. I’ll summarise the concept for you here so that we can keep going.

An affordance is an opportunity-for-action, specific to the capabilities of the entity carrying out the action. For example, a chair affords humans many opportunities-for-action; sitting, throwing, tipping over, wedging under things or using as a shelf.

Each one of these affordances exists because the properties of the chair (weight, surfaces, shape, size) ‘match’ our physical capabilities (strength, vision, grip, bodyform). On the other hand, to a hedgehog, a chair affords hiding-under, but not sitting. Poor little chaps aren’t big or tall enough for that. Unless you pick one up and set up on the seat. The world’s full of opportunities for action, meetings between the things offered by objects and our specific capabilities.

Crucially, some of these affordances will be so plain as to be self-obvious. Any object with a clear handle tends to communicate ‘gripability.’ In the case of mechanical soap dispensers, the large lever protruding from their face tends to communicate ‘pullability.’

Other affordances, especially affordances tied to automated actions, may be communicated by how something is designed. The thing about a lot of modern technology, it’s affordances are often not that discoverable. The capabilities exist, but they just aren’t visible.

Another example from my travels was a hand-sanitiser dispenser that required a rather ugly, after-market label to indicate how to use it. The dispenser was visible, but its design meant it wasn’t obvious where or how to interact with it.

You’ve surely seen this sort of ‘after-market’ amendment before. A way of providing a band-aid to the inadequacies of research and design.

Here’s another design with so little information communicated it’s practically obtuse.

Natural use interrupts proper function

Ignoring lack of refills or some other deep electronic fault, common usage seems, in my experience, to somehow obstruct or obscure their sensors. Is no-one testing these devices in high-volume, real-world conditions to see if natural use interfers with their mechanism? Like this example, a dispenser that, for the life of me, I couldn’t figure out how to make it work, no matter how much I waved my hands all over the entire thing. On closer examination, I suspected a dirty sensor.

Soap dispensers may not respond to everyone

Finally, if it is indeed true, there is a disappointing lack of racial representation in the people used to help inform the design of automated dispensers. Individual reports suggest some automatic soap dispensers don’t trigger correctly if someone doesn’t have a skin colour that matches the machine’s expectation.

One case I found was in a video by T. J. Fitzpatrick, who is black, and discovered an automatic soap dispenser that didn’t register his hands, though it did work for his white colleague. This may not be a single isolated case. In 2017, Gizmodo reported a Facebook employe in Nigeria showing how the automated soap dispenser worked for his white colleague but not himself. The explanation given in the second case was that cheaper automated soap dispensers used an optic sensor that wasn’t able to bounce back enough light for someone who had darker skin, thus failing to trigger the actuator.

Back to push pump soap?

So are automated soap dispensers a human centred design fail and we should go back to the mechanical pump models? Not quite. The mechanical push methods mostly work, but they present their own set of interaction hazards, given they require specific mechanical capabilities that are sometimes hard to achieve, like with stiff operating levers or awkward angles. Mechanical machines can still break, given the high volume of mechanical action and force placed upon the levers. We certainly still have to wash our hands and the evidence seems to stand that automated, touchless devices are a good way of helping control the spread of disease.

One option, highlighted by Iqbal and Campbell is to use new, more sophisticated sensors. They note:

“It is time to turn towards new solutions as the touchless technology is an evolving process. The innovations in the eye tracking technology and effective use of eye patterns can bring new interaction techniques as standard features in new generation smart devices for human communication. With the recent progress in hand tracking technology with deep learning, touchless typing can become more realistic without the need of wearing any sensors. High initial cost involved with touchless technology products and their implementation is the major bottleneck with adoption but it is decreasing with time. The other major resistance is from the user side, but COVID-19 has helped people to understand the need and most of us understand why avoiding touching in a public place is important.” (P. 10, Time for Touchless)

A soap dispenser that uses cameras and human recognition? Maybe there’s a solution there, but pardon me if I began to get Orwellian vibes at that sort of technology. Especially in a bathroom.

Ironically, the more I think about the problem, spiralling outward to consider the entire lifecycle of an automated soap dispenser, the more new challenges appear. Have you ever seen one of those manual or automated soap dispensers with a big reservoir of soap? The one that looks like it’s topped up from some sort of jug. Turns out that these ‘bulk fill’ liquid soap dispensers can actually become contaminated. This would mean each hand wash might actually make contamination worse.

Zapka et al. in their frighteningly titled “Bacterial Hand Contamination and Transfer after Use of Contaminated Bulk-Soap-Refillable Dispensers,” published in 2011 note:

“Gram-negative bacteria on the hands of students and staff increased by 1.42 log10 CFU per hand (26-fold) after washing with soap from contaminated bulk-soap-refillable dispensers. In contrast, washing with soap from dispensers with sealed refills significantly reduced bacteria on hands by 0.30 log10 CFU per hand (2-fold)… These results demonstrate that washing with contaminated soap from bulk-soap- refillable dispensers can increase the number of opportunistic pathogens on the hands and may play a role in the transmission of bacteria in public settings.” (Zapka et al.)

Let’s restate. The mechanism of infection could be a contaminated soap reservoir, independent of any automated or mechanical delivery system.

“Liquid soap can become contaminated with bacteria and poses a recognised health risk in health care settings. In particular, bulk-soap-refillable dispensers (ones in which new soap is poured into a dispenser) are prone to bacterial contamination, and several outbreaks linked to the use of contaminated soap in health care settings have been reported…The Centers for Disease Control and Prevention (CDC) “Guideline for Hand Hygiene in Health-Care Settings” addresses this risk in a recommenda- tion: “Do not add soap to a partially empty soap dispenser. This practice of ‘topping off’ dispensers can lead to bacterial contamination of soap”… Sealed-soap-dispens- ing systems, in contrast, are typically refilled by inserting into the dispenser a new bag or cartridge of soap that usually includes a new nozzle.” (Zapka et al.)

Think about that next time you see someone topping up a bathroom soap dispenser. Luckily there are soap dispensers that seem to use sealed sachets that can remain uncontaminated during refill. Though this example both has a mechanical press and the sachet creates more trash…

It all this feels a bit overwhelming, perhaps there’s always interesting older technologies, like felted soap? Useful at home perhaps, to keep soap grip-able (another affordance) but not good for high volume public environments.

Though I was amused to find this wonderful hand-cranked soap flaker from Germany.

Despite all the research and design challenges, I think the general theory of automatic soap dispensers is the right meeting of time, technology and need. But this under-sung category of general everyday product just needs a little more research and design, real world field tests and an assurance that the devices are clear, easy to use, reliable and accessible to all.

Updated 14 February 2023 –Extra images, a few lines of commentary and additional references.

References

Bingi, W. (2021, April 6). Automatic Handwash Station Soap Dispenser (Image, CC BY-SA 4.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:A_touchless_handwashing_tap_and_solid_bar_soap_dispenser_kit.jpg

Bullenwächter. (2011, June 24). GRUNELLA Soap Flaker (Image, CC BY 3.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Seifenmühle.jpg

Chuan, S. G. (1991). Automatic Cleaning-liquid Dispensing Device (Patent No. US4989755A). United States Patent and Trademark Office (USPTO). https://patents.google.com/patent/US4989755

Fussell, S. (2017, August 17). Why Can’t This Soap Dispenser Identify Dark Skin? Gizmodo. https://gizmodo.com/why-cant-this-soap-dispenser-identify-dark-skin-1797931773

Griffith, C. J., Malik, R., Cooper, R. A., Looker, N., & Michaels, B. (2003). Environmental surface cleanliness and the potential for contamination during handwashing. American Journal of Infection Control, 31(2), 93–96. https://doi.org/10.1067/mic.2003.62

Hongsoongnern, P., Britton, A., & S, V. (2016). Reduced Germ Exposure from Changing out Manual Soap and Sanitizer Dispensers to Touchless Closed System Dispensers. American Journal of Infection Control, 44(6), S78. https://doi.org/10.1016/j.ajic.2016.04.084

Infection Control Today. (2008, July 24). Going Touchless is a High-Tech Solution to Hand Hygiene Compliance. Infection Control Today. https://www.infectioncontroltoday.com/view/going-touchless-high-tech-solution-hand-hygiene-compliance

Iqbal, M. Z., & Campbell, A. G. (2021). From luxury to necessity: Progress of touchless interaction technology. Technology in Society, 67, 101796. https://doi.org/10.1016/j.techsoc.2021.101796

Lee, E. (1902). Reservoir For Dispensing Liquid Soap (Patent No. US708652A). United States Patent and Trademark Office (USPTO). https://patents.google.com/patent/US708652A/

Oka21000. (2013, March 29). Kintetsu Japanese Soap Automatic Dispenser (Image, CC BY-SA 3.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:KINTETSU50000_SANITARY4.JPG

PALMBLA, E. S. (1897). Syrup-drawing Device (Patent No. US579006A). United States Patent and Trademark Office (USPTO). https://patents.google.com/patent/US579006A

Pavlov, S. (2020, May 20). Bobrick Surface-Mounted Soap Dispenser, Model B2111 (Image, CC BY-SA 4.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Bobrick_Surface-Mounted_Soap_Dispenser,_Model_B2111,_img01.jpg

Plenke, M. (2015, September 9). The Reason This “Racist Soap Dispenser” Doesn’t Work on Black Skin. MIC. https://www.mic.com/articles/124899/the-reason-this-racist-soap-dispenser-doesn-t-work-on-black-skin

Ser Amantio di Nicolao. (2022, April 12). Cintas Soap Dispenser (Image, CC BY-SA 4.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Orange_Cintas_soap_dispenser.jpg

Sheppard, W. (1865). Improved Liquid Soap (Patent No. US49561A). United States Patent and Trademark Office (USPTO). https://patents.google.com/patent/US49561A/

TaurusEmerald. (2022, February 5). A Gojo-branded Soap Dispenser at Love’s Travel Stop (Image, CC BY-SA 4.0). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Love%27s_Travel_Stops_Gojo_Soap_Dispenser.jpg

WURTZ, R., MOYE, G., & JOVANOVIC, B. (1994). Handwashing machines, handwashing compliance, and potential for cross-contamination. American Journal of Infection Control, 22(4), 228–230. https://doi.org/10.1016/0196-6553(94)99001-8

Zapka, C. A., Campbell, E. J., Maxwell, S. L., Gerba, C. P., Dolan, M. J., Arbogast, J. W., & Macinga, D. R. (2011). Bacterial Hand Contamination and Transfer after Use of Contaminated Bulk-Soap-Refillable Dispensers. Applied and Environmental Microbiology, 77(9), 2898–2904. https://doi.org/10.1128/AEM.02632-10