What Does Bamboo Lyocell Look Like Under a Microscope?

The short version: Under a scanning electron microscope, CleanBamboo® bamboo lyocell is a smooth, uniform cylinder about 10 microns across. There are no grooves, no serrated edges and no fibrillation, even at 3,000x magnification. A smooth starting fibre is one reason the finished fabric feels cool and smooth against your skin. In published microscope studies, conventional viscose (rayon) fibre, by contrast, has a lengthwise-striated surface and an irregular, lobed cross-section, and cotton is a flattened, twisted ribbon.

Lyocell and viscose are two very different ways of turning bamboo into fibre, and published research shows the difference. These images show ours.

Why we put our fibre under a microscope

Most bedding brands describe their fabric with adjectives. I’ve worked with this fibre long enough to know it’s different. But knowing isn’t proof, so I wanted something you could see for yourself.

In January 2024, we sent raw CleanBamboo® fibre, before it was spun into yarn or woven, to a third-party textile research lab. They imaged it on a scanning electron microscope (a Zeiss Auriga 40) at magnifications from 100x to 3,000x. It’s the same fibre that goes into everything we make, from our sheets to our towels.

The images below are unedited. We’ve left the microscope’s data bar on each one so you can check the magnification, scale and date.

What does bamboo lyocell look like under a microscope?

At 100x, a pinch of CleanBamboo® fibre looks like a loose tangle of fine, even strands. Each fibre is long and the same width from end to end.

CleanBamboo® fibre at 100x magnification. Scale bar 100 microns. SEM image, January 2024.

At 300x, you can follow individual fibres across the frame. The width doesn’t swell, taper or pinch along the length.

CleanBamboo® fibres at 300x. Scale bar 20 microns. SEM image, January 2024.

At 1,000x, the surface comes into focus. Each fibre is a smooth cylinder, roughly 9 to 10 microns across, measured against the scale bar. A typical human hair is several times wider, at around 50 to 100 microns. There are no lengthwise striations and no rough skin.

CleanBamboo® fibres at 1,000x. Scale bar 10 microns. The smooth, rounded surface has no grooves. SEM image, January 2024.

At 3,000x, we’re looking at a strip of surface about 38 microns wide. There’s no fibrillation (the tiny hair-like splits lyocell can develop when it’s rubbed while wet, as in washing) and no cracks. The odd speck you can see on some fibres is dust or residue from handling the sample.

A single CleanBamboo® fibre at 3,000x. Scale bar 2 microns. No fibrillation or surface damage is visible. SEM image, January 2024.

We didn’t find fibrillation in any of the 16 images the lab took, and you can see them all in the gallery at the end of this post. Since this is raw fibre, it shows the surface before spinning, weaving or washing.

Why does a smooth, even fibre matter?

Fibre shape isn’t a lab curiosity. It shapes three things you notice in bed.

Softness. A smooth, round fibre has less surface friction than a striated or ribbon-shaped one, so it tends to glide over skin instead of catching. That’s what people describe as the “silky” feel of CleanBamboo®.

Cool to the touch. A smooth fibre makes close contact with your skin, which helps heat move away from it quickly. That’s the cool feeling when you first get into bed, and it shows up in testing: our Signature Sateen sheets are cooler to the touch than leading sateen sheets in third-party Q-max testing.

Durability. Lyocell fibres have higher crystallinity and higher wet strength than viscose, which is why they hold up better through repeated washing (Zhang et al., 2018). In that review, lyocell’s crystallinity index was 0.44 against 0.25 for viscose, and viscose lost about half its tensile strength when wet, while lyocell kept most of its strength. The clean surface in these images is consistent with that structure. In third-party testing, our Signature Sateen was rated highest for pilling resistance vs leading sateen sheets, before and after 20 washes, and meets the 10,000-rub abrasion standard.

The flip side of lyocell’s tightly ordered structure is that rough, hot washing can fibrillate it, so care still matters. Our guide to washing bamboo sheets covers the basics.

How does CleanBamboo® compare with viscose and cotton?

We don’t yet have lab images of viscose and cotton taken under identical conditions, so the comparison below draws on published fibre science rather than our own micrographs.

Sources for the viscose and cotton rows are listed at the end of this post.

Is this the same for all “bamboo” sheets?

No. Most bamboo sheets on the market are bamboo viscose (rayon), which is made by a different chemical process and has the striated, irregular fibre described above. CleanBamboo® is bamboo lyocell, produced using a proprietary process in a closed-loop system that captures and reuses the organic solvent and recovers most of the process water.

In published studies, the two look different under the microscope, so fibre shape tells you whether you’re looking at lyocell or viscose. What it can’t tell you is whose lyocell it is. Bamboo lyocell and wood-based lyocell like TENCEL™ look much the same at this scale. The differences are in the raw material, the process and what’s independently verified. For more on how the fibres differ in sourcing and processing, read our guide to bamboo viscose vs bamboo lyocell.

The finished fabric is tested too. Our Signature Sateen sheets, quilt covers and pillowcases are certified to OEKO-TEX® Standard 100, meaning they’re independently tested for over 1,000 substances that could harm your health.

If you’d like to feel the difference for yourself, our Signature Bamboo Sheet Set is made from this same fibre. Run hot at night? Our guide to cooling bed sheets covers what actually helps.

Sources

• Zhang, S. et al. (2018). “Regenerated cellulose by the lyocell process, a brief review of the process and properties.” BioResources 13(2), 4577–4592. bioresources.cnr.ncsu.edu
  
• International Textile Center, Texas Tech University, with Cotton Incorporated (2001). Cotton Fiber Development and Processing: An Illustrated Overview. cottoninc.com
  
• OEKO-TEX® Standard 100 certificate SH025 285270 TESTEX, Product Class I. Look it up at oeko-tex.com/standard100.
• Scanning electron microscopy of raw CleanBamboo® fibre, commissioned by ettitude from a third-party textile research lab. Zeiss Auriga 40, January 2024.

About the author

Phoebe Yu is the founder and CEO of ettitude, the brand behind CleanBamboo®. She believes the best way to judge a fabric is to look at what it’s made of, all the way down to the fibre.