PLAN C: HYJEIA: A Low-cost UV-C Unit

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PLAN C: HYJEIA: A Low-cost UV-C Unit


Two hours outside of Tokyo in Chiba prefecture is Hackerfarm, a hackerspace that applies technology to growing things like potatoes. Christopher Wang, better known as Akiba, is thinking that potatoes would feed a lot of people if food shortages result from COVID-19. The experiment is called Project Potatohead — A Farm-to-Foodbank Initiative. However, Akiba is better known for hardware hacking. He is currently working on the Hyjeia Project, a low-cost, open-source decontamination unit that allows for N95 mask reuse.

Read more articles about Plan C: What makers are doing to combat Covid-19


It’s not the first project of his that came as a response to a disaster. As a co-founder of Tokyo Hackerspace, Akiba had been an instrumental part of Safecast, which was a civic response to the earthquake and Fukushima nuclear reactor meltdown in March 2011. Because the Japanese government did not make public information about local radiation levels, citizens did not know if they were being exposed to harmful levels of radiation. The Safecast team designed handheld Geiger counters to measure radiation levels in real-time and report the results of a map. Some of them drove through the country taking measurements and crowdsourcing a map showing radiation levels.

In a Make: interview with John Baichtal in March 2011, Akiba described the response by the hacker/maker community, which seems relevant today:

Hackerspaces foster a maker culture where you’re encouraged to take apart, modify, and build things. In normal life, you can pretty much buy anything that you would need for everyday living. But in a disaster scenario, this all breaks down. At that time, normal life ceases and you suddenly need a lot of things customized to a particular situation. Geiger counters were devices that used to be only purchased by people working with radioactive materials, paranoid militia, and weather geeks. Now they are becoming an everyday item in Tokyo.

…if a major disaster were to strike an area that had an active hackerspace, we believe that the members of the hackerspace would be the first people to pull the community together. Hackerspaces have tools and members with knowledge about how to make things from scratch and modify devices to suit their needs.

A bGeigie Nano outside of its protective Pelican case. (Source: Make:)

Eric Weinhoffer wrote about the Safecast project in Make: magazine.

Akiba’s new project is named after Hyjeia, the Greek goddess of cleanliness and it seems related to Safecast. The decontamination unit consists of a UV-C light array and a dosimeter that measures the intensity of the UV light over time, which irradiates pathogens. “We’re trying to use open-source hardware and software to bring the cost of the equipment down from around $50,000 to around $100–$200,” he said. He sees these units being used outside of hospitals where supplies of masks are limited and re-using decontaminated masks to prolong their use is a good option.

Before explaining his decontamination unit in more detail, Akiba told me that the decontamination protocol published by the University of Nebraska Medical Center, which he read about in a March 30th article in the New York Times, was the inspiration for this project and it established a framework that saved him a lot of extra trial and error.

During the Ebola outbreak in Africa, the University of Nebraska Medical Center was one of a few hospitals in the US who were set up to handle Ebola patients — doctors who were infected in Africa and brought back to the US for treatment. The University of Nebraska Medical Center “knew how to deal with infectious disease,” said Akiba. “They were using ultraviolet lights (UV-C) radiating 360 degrees to decontaminate a room. It was paired with a dosimeter to measure the dosage.” They had done the research to know what dosage was required to inactivate the Ebola virus. “They were able to calculate how long they needed to keep the UV-C lights in the room,” said Akiba. This kind of sterilization is called UltraViolet Germicidal Irradiation (UVGI), which damages the DNA of the virus so that it cannot reproduce.

“For COVID-19, as they started running low on face masks,” explained Akiba, “they decided to use UV-C lights to decontaminate face masks and they created a whole protocol around how to do it.” This protocol, which is the detailed documentation of the process of using UV-C lights for sterilizing masks, is what Akiba relied on to build his own decontamination unit. “It’s like having an operator’s manual,” he added. It’s not enough to just have the technology for decontamination — UV-C lights and the ability to monitor them, but having the procedures for using the technology, describing the specific actions that others can follow, is essential.

“We do a lot of projects with the World Bank and right now, with the International Rice Research Institute. So we work with developing countries,” said Akiba. “A lot of people go into those areas and they think ‘I’m going to bring this technology, it’s going to solve all the problems.’ But what it really is about are the systemic issues, the process and the people — those are the real problems that we deal with.” He thinks it’s the same thing with the hospitals now. “They just want a tool and a manual on how to use it,” he said. “So if Nebraska created the manual, then we could just work on creating the low-cost tool.”

Akiba’s innovation would be building an open-source decontamination unit using cheaper parts that were easy to find. But he would have to test all those parts to be sure they really worked as he wanted.

For example, the two UVGI lights used in the University of Nebraska Medical Center cost $25,000 each, he told me. “A rural clinic or a hospital in a developing country would not have a $50,000 budget to buy these special lights,” he said. He wanted to use 40-watt UV-C lights that fit into fluorescent light fixtures and are widely available.. “You can buy UV-C germicidal fluorescent lights, the bulbs, which are mercury bulbs, for $20 a piece,” he said. “It’s a huge differential because one is a specialty bulb and the other is mass-produced but they are both mercury bulbs.”

The first prototype that he built, called Nukebox, arranged the inexpensive UV-C fluorescent lights in a small box, seven centimeters away from the objects to be sterilized. It worked.

“The next thing was how to measure the light intensity.” he said. “Light intensity can be converted into dosage.” That means the amount of exposure to the light over time required to eliminate the virus. “Dosimeters measure radiation, and UV-C is essentially radiation,” said Akiba, who thought it reminded him of the radiation sensors he used in Safecast.

Akiba wrote in the Nukebox how-to:

I’m using a 10W germicidal fluorescent bulb with a rated output of 2.7W of UV-C light (UV light at 254 nm). This light theoretically puts out 1,364 μW/cm^2 of intensity at a point 7 cm away. …

The Covid-19 virus requires 5,000 μWs/cm^2 (5 mJ/cm^2) for sterilization. Based on the above formula, it would take 3.67 seconds of UV irradiation to inactivate the virus. There are other factors to consider though such as UV light warm up time, inaccuracies with the theoretical model, etc which is why you see people irradiating objects anywhere from 3 minutes to 30 minutes.

Akiba found that he could get cheap UV photodiode sensors on Amazon or eBay. This UV Detection Sensor mounted on an Arduino-compatible shield cost about $3 US. “They’re actually UV-A sensors but if you look at the data sheet, the sensitivity curve shows they cover the UV-C band at 260 nanometers, which is what you want to inactivate viruses.” He called this prototype Nukemeter. “I had the theoretical calculations of the intensity,” he said, “but I wanted to see my own calculations.” In other words, he could have relied on how things were supposed to work but instead he wanted to know and quantify how well they actually worked.

In building the Nukemeter, Akiba started collecting data on how long it takes the UV-C lamps to warm up. About one minute was enough to get 80% of the light’s intensity. Then he tested to see if the intensity varied along the axis of the bulb. “I was surprised to find that there was very significant deviation in the light intensity” along the bulb with the weakest levels at the ends. In a decontamination box, the positioning of masks off-center would mean they received lower amounts of irradiation. “The nice thing about UVC light is that it’s just time dependent,” said Akiba. If you have weaker UV light sources, then the exposure needs to happen over a longer amount of time.

He wrote software in Arduino to upload the data from the dosimeter to the computer for additional analysis and record-keeping.

For the next stage of the project, building a full-scale decontamination unit, Akiba abandoned his “nuke” naming scheme, which he wrote that it sounded too “bro-ey.” Hyjeia became the new project name for the room-sized unit. The unit is an array of four UV-C lights mounted on a wooden frame and a dosimeter, which can be used in the field to verify and test that the system works as it should outside of Hackerfarm. At a larger scale, Akiba says “it’s a factor of time and intensity and those are the two parameters you can work with.”

Akiba summarized his work: “It’s not cutting-edge rocket science. It’s essentially shining a light and then measuring it. But I think for me the important thing was being able to connect the two. So, there’s an operating manual, and then I’m a toolmaker. How do you make a tool for this?”

His goal is to get the equipment cost down to a couple of hundred dollars so that it can be built in hospitals that can’t afford expensive decontamination units as well as other places in communities where workers may not have a reliable supply of masks.

“There’s almost no excuse to run out of protective equipment because you can also decontaminate what’s already there based on medical evidence,” said Akiba. “And I feel like that’s important.”


Project Image sources: Hackerfarm

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DALE DOUGHERTY is the leading advocate of the Maker Movement. He founded Make: Magazine 2005, which first used the term “makers” to describe people who enjoyed “hands-on” work and play. He started Maker Faire in the San Francisco Bay Area in 2006, and this event has spread to nearly 200 locations in 40 countries, with over 1.5M attendees annually. He is President of Make:Community, which produces Make: and Maker Faire.

In 2011 Dougherty was honored at the White House as a “Champion of Change” through an initiative that honors Americans who are “doing extraordinary things in their communities to out-innovate, out-educate and out-build the rest of the world.” At the 2014 White House Maker Faire he was introduced by President Obama as an American innovator making significant contributions to the fields of education and business. He believes that the Maker Movement has the potential to transform the educational experience of students and introduce them to the practice of innovation through play and tinkering.

Dougherty is the author of “Free to Make: How the Maker Movement Is Changing our Jobs, Schools and Minds” with Adriane Conrad. He is co-author of "Maker City: A Practical Guide for Reinventing American Cities" with Peter Hirshberg and Marcia Kadanoff.

View more articles by Dale Dougherty


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