# A versatile snap chip for high-density sub-nanoliter chip-to-chip reagent transfer

## TL;DR

A new snap chip enables precise and high-density transfer of reagents between microscope slides, improving microfluidic applications.

## Contribution

A novel double transfer method increases spot density and reduces misalignment in snap chip technology.

## Key findings

- The snap chip achieved 625 spots per cm² with <40 μm misalignment.
- It quantified 50 proteins in 16 samples with pg/mL detection limits for 35 proteins.
- A 4-plex enzyme inhibition assay analyzed 128 conditions with precise timing.

## Abstract

The coordinated delivery of minute amounts of different reagents is important for microfluidics and microarrays, but is dependent on advanced equipment such as microarrayers. Previously, we developed the snap chip for the direct transfer of reagents, thus realizing fluidic operations by only manipulating microscope slides. However, owing to the misalignment between arrays spotted on different slides, millimeter spacing was needed between spots and the array density was limited. In this work, we have developed a novel double transfer method and have transferred 625 spots cm−2, corresponding to >10000 spots for a standard microscope slide. A user-friendly snapping system was manufactured to make liquid handling straightforward. Misalignment, which for direct transfer ranged from 150–250 μm, was reduced to <40 μm for double transfer. The snap chip was used to quantify 50 proteins in 16 samples simultaneously, yielding limits of detection in the pg/mL range for 35 proteins. The versatility of the snap chip is illustrated with a 4-plex homogenous enzyme inhibition assay analyzing 128 conditions with precise timing. The versatility and high density of the snap chip with double transfer allows for the development of high throughput reagent transfer protocols compatible with a variety of applications.