# Liquid‐in‐Liquid Prints: High‐Density Biochemically Encoded Information Preserved in Microdroplet Arrays

## TL;DR

Scientists created a new way to store information in liquid droplets, enabling precise biochemical encoding of images, codes, and text.

## Contribution

The work introduces a novel method for deterministic programming of information in microdroplet arrays using liquid-in-liquid printing.

## Key findings

- Microdroplet arrays can preserve biochemical information with high spatial resolution and precise composition.
- Information such as images, QR codes, and text can be encoded and decrypted through phase transitions.
- The method enables error correction and information storage in liquid-state systems.

## Abstract

Liquids are dense repositories of information, challenged only by how well their compositions are defined, preserved, accessed, or measured. The precise spatial patterning of solutes within a bulk liquid is challenging since diffusion disperses local concentrations and thereby attenuates functionality. Herein, a new concept is introduced for writing and preserving information in the liquid state through liquid‐in‐liquid microdroplet array printing. This technology produces fine resolution, 2D liquid structures, composite of indexed water‐in‐oil droplet pixels each with a precise composition, a high spatial resolution and a tight inter‐pixel pitch. With extreme control over droplet composition and by applying standard and custom encoding schemes, various forms of information are written biochemically such as images, QR codes, text characters and words. As a composite material, reversible phase transitions between dissolved liquid and crystallized solid states control information encryption and decryption. Compared to current liquid printing and chemical encoding paradigms, ours introduces a fundamentally new precedent for deterministically programming information release, exchange or decay without stimuli or physical processing. Further computational principles such as error correction and information storage are demonstrated. These micro‐liquid patterns are relevant to any application based on precise liquid handling such as information theory, materials design and biological assays.

This work introduces a novel approach for encoding and storing information in the liquid state in microdroplet arrays. These liquid‐in‐liquid prints are generated by a droplet printing system capable of dynamically setting the composition of each droplet pixel. Information in the form of color images, QR codes, text characters, words and basic programmes are biochemically written into micro‐liquid patterns.