To understand the Sun’s impacts on Earth, NASA initiated the Living with a Star program in 2001, and began developing a key research satellite: the Solar Dynamics Observatory (SDO). One of the instruments created for the SDO was the Extreme Ultraviolet Variability Experiment (EVE), tasked with measuring extreme ultraviolet (UV) radiation, which plays a key role in atmospheric heating and satellite drag. In 2005, Goddard Space Flight Center scientist Shahid Aslam joined other researchers in developing EVE.
A focus of Aslam’s work was experimenting with different ways of measuring extreme UV radiation. Silicon semiconductors have been used traditionally as detectors, but a drawback is they take in both UV and visible light. Filters are used to isolate the ultraviolet signal, but the results aren’t ideal. To sidestep the filtration process, the team looked into wideband gap semiconductors: chemical compounds that detect a narrower range of wavelengths on the electromagnetic spectrum. In particular, the team worked with compounds that detect only UV light.
It was early on in the project while experimenting with different compounds that Aslam noticed that a few of them detected bands of wavelength in the UV spectrum that held special significance for human health — areas where humans experience biological effects due to Sun exposure. Of the many types of UV light, UVA and UVB play important roles in health since their rays can pass through the atmosphere and make contact with Earth’s surface. Whether they’re friend or foe depends on the amount of exposure: Our bodies need UV light to produce vitamin D, critical to building bone density and supporting brain and immune system function, but too much sunlight can cause sunburn, premature aging, and skin cancer.
To gauge how much sunlight is too much, scientists have developed what’s known as the erythemal UV index, which highlights the durations at which UV wavelengths, when set at certain power quotients, will likely cause erythema, or reddening of the skin due to inflammation. Wouldn’t it be great, Aslam thought, to develop some kind of device that measures UV exposure in a way that allows people to manage their daily Sun intake?
He brought the idea up with marketing guru Karin Edgett, and the pair moved forward with developing the product. In his spare time, Aslam began working on the technical development, which included formulating algorithms and homing in on a proficient detector compound; Edgett tackled marketing and branding. The result — a UV light-detecting activity monitor — received recognition in 2011 when it won first place in the Consumer Products category in the Create the Future Design Contest, presented by Tech Briefs Media Group, the publishers of NASA Tech Briefs.
Buoyed by the initial reception, the pair formed SunFriend Corporation and moved forward with further development. In April 2014, after receiving positive reviews in trade shows the previous year, the UVA+B SunFriend was put on the market.
UVA+B SunFriend activity monitor comes at a time, Edgett said, when one in five people in the United States will get skin cancer in his or her lifetime. On the flip side, in some regions of the world, vitamin D deficiency is considered a pandemic.
To use SunFriend, a user first selects his or her level of skin sensitivity on an 11-point scale, with 1 indicating the highest level of sensitivity and 11 the lowest. The device is then worn face-up on the wrist and left uncovered. Throughout the day, as UVA and UVB light hits the embedded semiconductor compound, it produces photocurrents indicative of how much radiation is coming in. A microchip processes that current, taking into account radiation strength, the ratio of UVA to UVB light, and the selected level of skin sensitivity. When the maximum recommended daily dose of UV light is reached, the LEDs on the face of the device will flash. Aslam said, “At that point, you apply sunscreen, go indoors, or put on clothing.”
Although SunFriend is still very new to the market, the company is already working on increasing its functionality, such as implementing Bluetooth technology so that information can be communicated to users’ smartphones for record-keeping and statistics.