In almost every region of the world, the spread of COVID-19 has made social contact dangerous. It is an airborne virus that can cause severe respiratory issues for those infected. Despite its unknown pathology, there is consensus that wearing respirators will prevent airborne infection, slowing the spread of the disease. This is especially essential for medical personnel. However, these masks become contaminated quickly and are in short supply (Goodnough, 2020), but they can be reused safely if they are sterilized. Many photos online show masks stored in paper bags between uses. This is a prime opportunity for mask sterilization which no product on the market addresses. Thus, this proposal describes the UV Pill Sterilizer, which fills this market void.
Figure 1 UV Pill Sterilizer rendered using Autodesk Inventor. Ng, J. (n.d.). UV Pill Sterilizer.
The UV Pill Sterilizer is a portable unit for sterilizing respirator masks in the field so they can be reused by medical personnel. This drop-in solution relies on 4 UV LEDs, mounted on the sides and powered by a battery enclosed in the housing. The pill can be dropped into any reflective light-proof container, such as a popcorn bag, a potato chip bag, or a normal paper bag covered with aluminum foil. It is activated with the remote switch and agitated for 3 minutes, achieving 99.9% sterilization. It is recharged with a microUSB cable. There have been other inventions that rely on UV sterilization, but they are neither affordable nor portable, nor are they tailored toward respirator masks. The UV Pill Sterilizer provides a more cost-effective and efficient approach. The open sourced design, parts, and manufacture all will allow it to be available for distribution in as soon as one month.
Other Engineering Innovations
Most of the UV-based sterilization equipment on the market is too expensive for personal use, ranging from $1,000 to $120,000 (Nugent, n.d.). They are also large and need to be plugged in, designed for sterilization of large volumes (Nugent, n.d.). The UV Pill Sterilizer is expected to cost $46.49 in materials, fits in a pocket, and can be recharged via microUSB. This will prolong the lifespan of respirator masks, and consequently, the safety of healthcare workers.
One such product is the Air Science Stainless Steel UV-Box Sterilization Chamber. The market cost is $1,694 and weighs a total of 75 pounds, and runs on grid power (“Air Science”, n.d.). Although effective for mass sterilization of masks, it does not address the need for personal sterilization.
There have been other open source efforts to build a UV sterilization device. The UV-C Sterilization Cabinet is expected to cost around $50 (Deeplocal, 2020) and is in many ways similar to the proposed UV Pill Sterilizer. However, like the Air Science UV-Box, it relies on grid power and utilizes a large box as the chamber. This makes it unsuitable for field use by essential workers.
Lastly, the PULUZ 30cm UV Light Germicidal Sterilizer Disinfection Tent Box is perhaps the most similar to the proposed UV Pill Sterilizer, but still does not address the current novel needs of healthcare staff. It is a UV light embedded into a collapsible container, which is a step forward from the rigid cabinets of the other products. However, it still requires an external power source and is a 1-foot large cube (Puluz, n.d.). This is not ideal for personal use, especially in hospitals where floor space is valuable.
Technical description
Figure 2 Assembly drawing from Inventor 2020. Ng, J. (n.d.). Assembly.
Figure 3 Exploded assembly drawing from Inventor 2020. Ng, J. (n.d.). Exploded assembly.
Bill of Materials
The bill of materials, or BOM, is a full list and breakdown of raw materials and pre-assembled parts that are used in the product (See Appendix A, Table A1, for BOM). The Pill casing consists of aluminum and 3D printed plastic and fastened by steel screws. The rest of the BOM consists of electronics. These electronics, ordered from the power source to the light source, are the battery, the tail contact, the driver and charger circuit boards, the switch, and the LED, with wires for connections.
The aluminum used is 6061, which is the international industry code for a specific alloy that is strong, easily machinable, and corrosion-resistant (McMaster-Carr, n.d.). It is also lightweight and highly conductive to both heat and electricity, making it especially suitable for a handheld electronic light-emitting device. The 3D printed plastic specified is ABS plastic, which is commonly found in LegoTM bricks. ABS is well-known in the 3D printing community for its exceptional heat resistance, strength, and stability compared to other 3D-printed plastics. Lastly, the steel screws are made of stainless steel, which is steel that is highly resistant to corrosion.
The battery relies on lithium ion chemistry, which allows it to be reliable, high-power, and energy-dense (Samsung SDI Co., Ltd. [Samsung], 2014). It also provides 300 recharge cycles before losing 25% of its capacity when tested at its maximum power of 15 amps (Samsung, 2014). The expected power usage of the UV Pill Sterilizer is 2 amps, implying that it can be recharged many more times. It provides a nominal 3.6-volt charge.
The tail contact consists of a copper plate with a copper-alloyed spring attached. Copper is the second most conductive metal available at room temperature. The copper alloy retains this conductivity but adds elasticity to its physical properties, allowing the spring to be more flexible. This usage of copper will improve the flow of electricity to the LEDs.
The driver and charger circuit boards are made of printed circuit boards or PCBs. They consist of copper printed onto a fiber reinforced resin substrate, onto which electronic components are attached. This forms a stiff frame that is mounted onto the Pill casing.
The switch comes pre-assembled from the manufacturer, which utilizes a spring switch assembly with a stainless steel casing (EARU, n.d.). This solid stainless steel casing protects the inside switch assembly from mechanical damage.
Since the manufacturer sells the LED device mounted on a metal core printed circuit board, or MCPCB, this assembly was colloquially referred to as the LED. However, they consist of two separate components. The LED itself consists of a semiconductor that emits light, encased in a resin. It requires a voltage of 6 volts ( Due to its tendency to reach high temperatures, an MCPCB is used as a heatsink. The MCPCB material is copper, which is one of the most heat conductive materials available. It will easily and quickly draw heat away from the LED. The MCPCB also acts as a mounting device due to the tiny size of the actual LED.
The specified wires are 22AWG pure copper wires coated in PVC. 22AWG refers to the diameter of the wire and stands for American Wire Gauge. PVC, or polyvinyl chloride, is an insulator to electricity. It protects the copper from making unexpected electrical contact, causing shorts.
Function
Figure 4 Quarter section view from Inventor 2020. Ng, J. (n.d.). Quarter section.
The device can be comfortably held in one hand. See Appendix A, Figure A1 for its exact dimensions. To operate the device, the pill and a mask are placed into a reflective bag. The bag opening is rolled closed. The switch is held and the bag lightly shaken for 3 minutes. This will ensure full coverage of the UV light on the mask surfaces. The switch is then released, and the sterilized mask can be removed from the bag. To charge, connect a microUSB cable to the port.
When the button is pressed, the circuit is completed and the driver turns on. The negative charge from the battery travels from the battery’s right side, through the contact plate, end cap, and aluminum tube to reach the driver circuit. This path can be seen in the quarter section view in Figure 4. The positive terminal makes direct contact with the spring on the driver circuit. The driver circuit then regulates the 3.6 volts from the battery to the 6 volts required by the LED’s. The charger circuit is also connected to the battery and charges the battery when a microUSB is connected.
Labor Utilized for its Manufacture
The UV Pill Sterilizer was designed with ease of manufacturing in mind. It consists only of readily available, off-the-shelf parts and is able to be assembled with basic tools found on The City College of New York campus, robotics laboratories, or maker spaces (“Undergraduate laboratories,” n.d.).
The labor discussed will only include the labor of manufacture after the materials are ordered and have arrived. This requires 1 person working for 1 hour to produce 1 unit. First, 3D printing of the top cap is started and will run concurrently with the following operations, expected to take no more than 30 minutes. The aluminum tube and aluminum bar, which arrives in 6 ft long sections, will have to be cut to length with a band saw. They will then have holes for the screws marked and drilled, and the end cap will then need a cavity for the tail contact plate machined. This can be done manually with a drill press, or automatically with a computer-controlled CNC milling machine or router. When all this is finished, the 3D printed top cap will have completed.
Then electronics work begins. The spring is soldered onto the tail contact plate, then placed in the end cap cavity, which is then screwed onto the aluminum tube. Next, the battery is placed into the tube. The driver is placed over the tube and is held in place with the 3D printed top cap, which is screwed into place. The battery charging circuit is slid into the top cap. The LEDs are mounted onto the 4 sides of the assembly using thermal adhesive. Lastly, all the wires are soldered into place and sealed using epoxy, including the wire to the remote switch.
Costs and Time
The initial time for all the parts to ship is expected to take roughly 1 month. After parts arrive, finished products will be available for distribution within a week. The material costs per unit are $46.49, which excludes the cost of logistics. The full breakdown and BOM is available in Appendix A, Table A1. Labor costs are a function of skilled worker compensation, tooling costs, and worker fees. Given a wage of $15 per hour, combined with $5 of combined tooling costs and fees, the total cost to produce one unit is $66.49.
The cost of labor can be reduced by two options. Conventionally, manufacturers will turn to mass production, which will cut labor costs to about half. However, open sourcing the design and encouraging the maker space community to donate their time and resources to manufacture this product will eliminate all labor costs. One community, Make4Covid, has already distributed over 30,000 pieces of PPE with thousands of volunteers (Miller, 2020), making this a viable short-term option.
Design Process
Our group, the COVID Fighters, agreed that it would be appropriate to create innovation with a focus on the ongoing COVID-19 pandemic. We began with a brainstorming activity in which we listed innovations that piqued our interest. An early idea was a UV respirator which relied on passing air through an intense UV light. However, the issue with this design is that UV light needed to be high-intensity to properly sterilize the air, which would cause skin cancer if the skin is exposed for extended periods of time. Iterations on the design relied on other mechanisms of sterilization, such as rapid heating and cooling, but that proved to be too large and bulky and energy-inefficient. Eventually, we noticed that essential workers, especially healthcare staff, were storing their respirator masks in paper bags between shifts. There was a photo recently published on social media showing numerous paper bags, holding the masks of nurses, tacked to a wall (see Appendix B for photo). This inspired us to create an innovation to supplement this current storage solution to sterilize respirator masks. Our design constraints were:
- Must sterilize the mask in under 5 minutes
- Must be a portable and personal solution
- Must be deployable immediately by medical personnel
- Must be affordable
The UV Pill Sterilizer satisfies all these criteria. We conducted research on different UV LEDs and settled on one made by Seoul Viosys. This particular LED has already been proven to kill 99.9% of coronaviruses after 30 seconds of exposure in lab testing (Moore, 2020). Thus, the LED will be able to effectively sterilize a face shield in the field in under 5 minutes. The design for portability and deployability led us to add microUSB charging as a feature and keep it as small and minimal as possible. This also helped with affordability.
After the design was settled, the parts were created in the 3D modeling software Autodesk Inventor 2020. Each part of the BOM was modeled separately. After the individual parts were modeled, they were brought together into an assembly and connected together. This allows for rapid prototyping of the design and lets us verify that everything fits together. It also has many options to render video and images of the product.
Conclusion
The UV Pill Sterilizer can offer anyone who uses face masks a means to mitigate the number of crucial supplies being used. It is a cost-effective product that can be manufactured in bulk to be provided to the public in a matter of days. Thousands of UV Pill Sterilizers can be created through volunteer collaboration or mass production. It is a rechargeable battery, portability, and high disinfection rate help to keep respirators safe for reuse. There are other products that also use ultraviolet light for cleansing but none can match the convenience, efficiency, and economy of the UV Pill Sterilizer. It has the fastest cleansing time for its type and will help to keep essential workers safe from infection by COVID-19 and thus, will contribute to the eradication of the pandemic.
