# Bacterial cellulose sheet masks

How Komagataeibacter spins cellulose ribbons at an air-liquid interface, why the resulting hydrogel conforms to skin, and the limits set by pore size, hornification and water activity.

A bacterial cellulose pellicle is mostly water held in a nanofibril network, and almost everything a sheet mask does follows from that plus contact.

Source: https://en.bioecon.ru/docs/forestry-biomaterials/fibers-textiles/bio-face-masks/
Updated: 2026-09-04



A sheet mask is a delivery device with two variables: how well it stays in contact with skin, and what it releases while it is there. Bacterial cellulose — grown as a pellicle by acetic acid bacteria of the genus *Komagataeibacter* — is unusual on the first variable and constrained on the second, and both properties come from the same structure.

## How the pellicle is built

The bacterium takes glucose or fructose from a sugar-rich medium — coconut water and other fruit substrates are common — and polymerises UDP-glucose into β-1,4-glucan chains extruded through terminal synthase complexes arranged in a row along the cell. Chains from adjacent sites crystallise together as they emerge, so the cell lays down a ribbon tens of nanometres wide rather than isolated molecules. Because the organism is obligately aerobic, growth concentrates at the air-liquid interface, and the ribbons accumulate there into a coherent mat. That mat is the material: a random three-dimensional network of nanofibrils, of high crystallinity, holding water at up to around 99 % of its wet mass.

Chemically it is the same polymer as plant cellulose, but it is deposited without lignin, hemicellulose or pectin. It therefore needs no delignification — only alkaline washing to remove cells and medium — which is why bacterial cellulose is chemically pure by origin rather than by purification.

## Why it fits the face

The wet pellicle behaves as a compliant hydrogel with an extremely fine surface texture, so it drapes into the contours around the nose and eyes and makes continuous contact rather than tenting across them. Continuous contact is the whole point: it occludes, transepidermal water loss falls, and the stratum corneum takes up water from beneath. A hydrated stratum corneum is more permeable, so occlusion both hydrates and improves the passage of whatever the mask carries. Most of the visible immediate effect of any sheet mask is this hydration, and it is transient — the corneocytes give the water back within hours.

## Where the structure sets the ceiling

The same dense nanofibril network limits loading and release. The pores are small and the path through them is tortuous, so large molecules diffuse out slowly and incompletely, and the network is hydrophilic and essentially uncharged, so it carries water-soluble actives well and lipophilic ones badly — an oil-based serum has to be emulsified before the mask can hold it in any useful way.

Drying is close to irreversible. When a cellulose hydrogel is dried, adjacent fibrils are pulled together by capillary forces and lock by hydrogen bonding, a change papermakers call hornification; the sheet never re-swells to its original volume or conformability. Products are therefore shipped wet, which raises the second constraint: a nutrient-rich, high-water-activity gel is a good growth medium. It has to be preserved and sterilised, and sterilisation that is thorough enough for the substrate can degrade the actives it is carrying.

Production is also interface-limited. In static culture the pellicle grows at the surface, so yield scales with vessel area rather than volume, and thickness accrues slowly. Agitated culture is faster but tends to give pellets and irregular fibril networks instead of a coherent, drapeable sheet.