# Durable Janus membrane with on-demand mode switching fabricated by femtosecond laser

## TL;DR

This paper introduces a durable Janus membrane that can switch modes on demand, improving its mechanical strength and water transport capabilities for real-world applications.

## Contribution

The novel on-demand mode-switching strategy enhances mechanical durability and unidirectional water transport in Janus membranes.

## Key findings

- The membrane can switch between stretching Janus mode and releasing protection mode for robust water flow.
- It withstands harsh conditions like 2000 cycles of mechanical abrasion and 10 days of air exposure.
- The design is demonstrated as a durable fog collector in real-world environments.

## Abstract

Despite their notable unidirectional water transport capabilities, Janus membranes are commonly challenged by the fragility of their chemical coatings and the clogging of open microchannels. Here, an on-demand mode-switching strategy is presented to consider the Janus functionality and mechanical durability separately and implement them by simply stretching and releasing the membrane. The stretching Janus mode facilitates unidirectional liquid flow through the hydrophilic micropores-microgrooves channels (PG channels) fabricated by femtosecond laser. The releasing protection mode is designed for the in-situ closure of the PG channels upon encountering external abrasion and impact. The protection mode imparts the Janus membrane robustness to reserve water unidirectional penetration under harsh conditions, such as 2000  cycles mechanical abrasion, 10 days exposure in air and other rigorous tests (sandpaper abrasion, finger rubbing, sand impact and tape peeling). The underlying mechanism of gridded grooves in protecting and enhancing water flow is unveiled. The Janus membrane serves as a fog collector to demonstrate its unwavering mechanical durability in harsh real-world conditions. The presented design strategy could open up new possibilities of Janus membrane in a multitude of applications ranging from multiphase separation devices to fog harvesting and wearable health-monitoring patches.

Janus membranes are highly valued for their unique water unidirectional transportation capabilities. Here, authors report an on-demand mode-switching strategy that significantly enhances the durability of the Janus membrane.