# A biofluid-repellent nanograss coating enhances flow of protein solutions and preserves transparency of glass capillaries upon exposure to blood

## TL;DR

A new transparent coating on glass capillaries repels blood and protein solutions, reducing resistance and staying clean.

## Contribution

A novel biofluid-repellent nanograss coating is developed for glass capillaries, enhancing flow and transparency.

## Key findings

- The coating reduces hydraulic resistance for protein-rich fluids by up to 50%.
- The capillaries remain transparent and clean after short-term blood exposure.
- The repellence effect is strongest in small tubes and at low Reynolds numbers.

## Abstract

A transparent and superhydrophobic (SHB) nanograss coating makes glass capillaries repellent toward protein solutions and blood. The coating is fabricated using atomic layer deposited alumina which is converted into grass-like alumina (GLA) by hot water treatment (HWT). The resulting tubes are transparent and highly repellent towards water and protein solutions (sliding angle <6° for a concentrated albumin solution). The biofluid repellence of the coating reduces hydraulic resistances for protein-rich biofluids, including fetal bovine serum, by 0–50% with the strongest effect for the smallest tubes and lowest Reynolds numbers. This work addresses a knowledge gap where previous studies have mostly focused on pure water for the drag reduction effect. The tubes also show a promising ability to stay clean and transparent on short term exposure to blood, unlike unmodified glass or polymer controls.

Superhydrophobic (SHB) glass capillaries are fabricated by depositing thin alumina and its conversion into grass-like alumina. The capillaries repel water and biofluids including blood which indicates their applications in blood contacting devices.