Ultraviolet radiation has long been known as a disinfecting agent for liquids, air and surfaces. Now with an increased need for sterilization in hospitals and public spaces, this technology has received more “light” in the public consciousness. As with most new technologies, there’s more to using a “UV light sanitizer”—specifically light in the UV-C range—than simply flipping a switch.
Wavelength of UV-C Radiation
Within the UV-C wavelength range, maximum germicidal activity occurs at the 265nm, though this varies depending on the organism. Even at the correct wavelength, however, light must actually hit the infected surface. This means that shadowy areas like those under a remote control or phone handset must be given special attention, and that lighting may need to be sourced from several positions. Objects may even need to be moved for multiple disinfection cycles during a cleaning.
Further inhibiting proper cleaning is the fact that humans can only withstand low doses of this light. Operators normally set UV sanitization lighting up in an area, leave, then come back when it’s done.
Alternatively, fixed lighting can be shielded in order to directly light only areas near the floor and ceiling, making its use safe for humans. While such a setup can be used continuously, the obvious disadvantage is that it’s leaving much of a room’s volume unaffected. Even so, such a static setup can be a good alternative in many situations.
The (Germ) Killer: Disinfection Robots
What is the best way to disinfect germs in a hospital, or in other situations where individual rooms are normally occupied, but are conveniently empty at regular intervals? Manual cleaning with chemical agents is still the first line of defense, but then you’d want a system that can be transported—or transport itself—to a potentially infected space, and go to work with its UV-C germ death beam. Ideally, it would generate a report on the process, provide some sort of remote interface, and shut down automatically, so as not to expose humans to this light.
In other words, you want a disinfection robot. In a time when keeping clean is on everyone’s mind, there is no shortage of options. Like in a good sci-fi movie, these robotic Hunter-Killers dispense biological entities with ruthless efficiency, but this time, they’re on our side. Here are a few of the weapons at humanity’s disposal:
Xenex LightStrike
Launched in 2010, the Xenex LightStrike disinfection robot repeatedly pulses UV-C light to kill germs. The device has been evaluated in over 35 peer-reviewed studies.
- • Movement: Human-powered
- • Power: Plug-in
- • Control/AI: Identifies high-touch surfaces to target for disinfection. External sensor unit identifies room entry to shut process down for human safety
- • Lighting Technology: Pulsed xenon; single element
- • Special Features: Mirrored lighting unit extends automatically and turns during germicidal process. Light retracts to form a rugged cleaning unit for transportation. Xenex has also developed an autonomous version for more open environments, but sees manual placement and setup as the most expedient method in most situations
THOR UVC Disinfection
Available since 2014, the THOR UVC disinfection robots feature an extendable lighting assembly, with 24 individual lighting elements.
- • Movement: Human-powered
- • Power: Plug-in main power; rechargeable battery to maintains settings
- • Control/AI: Tablet user interface; room entry sensor for automatic shutdown; lidar scanner used to map the room for light coverage; scanning at three different heights
- • Lighting Technology: 24 Philips Signify low-pressure mercury elements
- • Special Features: Automatically extends to different heights as needed (between 1.1m and 2.25m) to allow light to effectively reach different areas. In addition to building usage, unit is capable of emergency vehicle contamination per its easy transportation ability and adjustable height
SIFROBOT-6.5
Meant for a wide range of sanitation applications, the SISOF SIFROBOT-6.5 features autonomous operation and charging.
- • Movement: Self-powered at up to .45m/s in navigation mode
- • Power: Runs for 4+ hours per charge; capable of autonomous charging
- • Control/AI: Autonomous operation, with lidar, odometer, and gyroscope for navigation
- • Lighting Technology: Mercury vapor
- • Special Features: System draws in ambient air from the environment for purification
Hyper Light Disinfection Robot
Launched in 2016, the Mediland Hyper Light disinfection robot is manually transported into place It uses reflectors to aim six individual lights around the room.
- • Movement: Human-powered
- • Power: Plug-in
- • Control/AI: Onboard user interface and wireless Bluetooth tablet. Able to sense room entry for human safety
- • Lighting Technology: Six Amalgam lamps
- • Special Features: Cylindrical light reflectors rotate back and forth to aim beams during disinfection. These reflectors rotate outwards for storage and movement, acting as a protective shell
MIT Warehouse Disinfection Robot
Constructed by modifying an Ava Robotics telepresence robot to mount a UV-C lighting array, this robot is meant for use in large warehouse spaces. It demonstrates how different style robots could be adapted for germ fighting applications.
- • Movement: Self-powered
- • Power: Rechargeable
- • Lighting Technology: Four separate tubes in open configuration
- • AI/Control: Remotely operated via Ava Robotics Chassis; autonomous operation work-in-progress
- • Special Features: Able to cover a 4,000-square-foot warehouse space in ½ hour, with 90 percent efficiency when killing coronaviruses
UV-C Light Effectiveness In our current situation, guidance for avoiding infection has been fluid, and sometimes even conflicting. One might be understandably skeptical about a new “disease death ray”. In fact, UV-C for germ elimination in hospital settings has been gaining acceptance for many years.
A 2018 study in the American Journal of Infection Control notes that Clostridium difficile infection (CDI) rates at three units at the Mayo Clinic were cut by nearly 61% during a six month trial of UV disinfection using a Xenex unit. UV disinfection is also being used in other facilities, such as St. Joseph’s Children’s Hospital in Tampa, as well as in the VA system. According to one doctor who works at a VA hospital, they’ve been using a mobile disinfection device there for several years. In fact, the “burned room” smell after it finishes reportedly now evokes a feeling of cleanliness, analogous to what most people associate with a freshly bleached floor.
Extra challenges for hospital staff, those that work in warehouses and transportation, and anyone else that must be exposed to others on a daily basis are here with us for the time being. One can hope that the lessons we learn today about UV-C lighting and other disinfection methods can be applied going forward to provide a long lasting benefit to society.
