Scientists Tattoo Micro-Patterns on Tardigrades

Researchers have demonstrated a novel way to inscribe microscopic patterns on living organisms, using the resilient tardigrade as a model. The study, published in Nano Letters, explores a technique known as ice lithography to apply biocompatible designs onto the surface of living tissue, showing that this method can potentially extend to bacteria and other life forms.

Ice lithography on a microscopic scale

Microfabrication — the process of building devices on the micro- to nanoscale — is widely used in fields like electronics and photonics. It underpins technologies from microprocessors to solar cells and biosensors. But its potential use in biological systems has been limited by challenges in adapting the materials and processes to living tissues.

To bridge this gap, scientists employed ice lithography, which uses an electron beam to carve designs into a thin layer of ice deposited on a surface. The process involves freezing a protective coating over a sample and then exposing selected areas to the beam, which causes chemical reactions that leave behind a stable pattern once the ice sublimates.

Tardigrades, also known as water bears, are ideal subjects for this technique due to their remarkable survival abilities. These animals can endure extreme dehydration, freezing, radiation and even the vacuum of space.

Step-by-step micro-tattooing

To begin the process, the researchers induced a cryptobiotic state in the tardigrades by slowly dehydrating them. In this state, their metabolism drops to near-zero, allowing them to survive harsh conditions. Each dehydrated tardigrade was placed on a carbon-composite substrate and cooled to –143 degrees Celsius. They were then coated with a layer of frozen anisole, an organic compound.

An electron beam was directed at the frozen anisole to selectively alter its chemistry. Upon warming, unreacted anisole sublimated, revealing micro-patterns where the beam had triggered reactions. The surviving tardigrades were rehydrated and revived, many with visible microscopic designs still adhered to their bodies.

Patterns produced included geometric shapes and even a university logo, with line widths as small as 72 nanometers. Approximately 40% of the tardigrades survived the procedure, with no observable change in behavior after revival.

Toward applications in bioelectronics

The successful tattooing of tardigrades illustrates the potential of this method for constructing bio-compatible sensors or electronic interfaces on living tissues. Although demonstrated in an invertebrate, the technique could lead to broader applications in microbial systems or tissue engineering.

The researchers suggest that optimizing the conditions of the lithography process could improve survival rates and broaden its use across different biological models. Future research could explore embedding more complex circuits or sensors directly onto or within living organisms.

Reference: Yang Z, Wu S, Zhao K, Zhao D, Qiu M. Patterning on living tardigrades. Nano Lett. 2025;25(15):6168-6175. doi: 10.1021/acs.nanolett.5c00378

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