Firefly Portable Red Light Therapy Device

Light is a nutrient, and like any nutrient it only works if you're consistent about getting it. A device that needs an outlet and a dedicated room is a device you'll use less. Travel, road trips, hotel rooms and months across time zones all break the habit. The Firefly is built for exactly those moments. It's the world's first handheld, battery-powered COB light device: carry-on sized and able to run off a standard USB-C battery bank.

Two years for one battery: A COB chip draws far more power than the single diodes in typical handhelds, and no existing battery could hold that charge in a handheld form. That's why a device like this didn't exist. It took us two years to develop a battery that could, and that battery is what's patent-pending. It's also the honest reason the Firefly runs a 75W COB while our panels run 200W and up: 75W is the largest chip our battery can drive in a handheld. We publish that plainly rather than overstate it.

COB in your hand: 25 × 3W diodes are bonded directly to a substrate in a 1-inch array, with no housings and no gaps. A 60-degree cone lens directs the output instead of letting it scatter. The result is a dense, even beam from a device you hold in one hand.

Measured, not guessed: how we got to 8–12 minutes

Most brands give you a session time with nothing behind it. Here's ours, step by step.

1. We measured the light. Robert Hunt, author of The Blue Light Diet, measured the Firefly on camera with his own meter. At 6 inches it puts out about 20 mW/cm² of red and near-infrared light. That number is its irradiance: how much light power reaches each square centimeter of your skin. You can watch the full test in the second video.

2. We checked it against the research. Michael Hamblin's group at Harvard Medical School and Massachusetts General Hospital reviewed the light therapy literature. They found most studies use an irradiance of 5–50 mW/cm² and a dose of 1–20 J/cm² (Huang, Sharma, Carroll & Hamblin, Dose-Response, 2011). At 6 inches, the Firefly's 20 mW/cm² sits right in that irradiance range.

3. We did the math. Dose equals irradiance multiplied by time. At 20 mW/cm², every minute delivers about 1.2 J/cm², so 8 minutes is about 10 J/cm² and 12 minutes is about 14 J/cm². That's the middle of the research range.

4. Why not longer? The same research found that light follows a biphasic dose response: past a certain point, more light does less, not more. So longer isn't better. The right dose is.

We measure every light we make, on video, so you get real session times backed by research, not a number we made up.

The wavelengths: 630nm and 660nm red with 830nm near-infrared gives two peaks in the red window and one in the near-infrared. These are the ranges where cytochrome c oxidase, the mitochondrial enzyme at the center of photobiomodulation research, absorbs light most strongly. 630nm and 660nm work in the dermis (fibroblast activity, collagen production). 830nm penetrates centimeters into muscle, joint and connective tissue. 830nm is invisible to the eye, so wear the included goggles every session. You can also verify the peaks yourself: Robert measures them with his own spectrometer in the same video.

Why battery power matters: Flicker and magnetic fields in light devices come from AC power, the alternating current of the grid. The Firefly runs on DC from a battery, so there's no AC current at all. That means no AC-generated flicker and no AC-generated magnetic field, by design rather than by mitigation. Our panels handle the same physics with Meanwell drivers and a 12-inch session distance. The Firefly handles it by never touching the grid.

How to use it: Hold it 6 inches from the area you're treating for 8–12 minutes. If you're new to red light, start at 8 minutes. Moving it farther away lowers the irradiance, so stick to 6 inches for the times above to hold.