3D-glass molds for facile production of complex droplet microfluidic chips.

Miguel Tovar,Sundar Hengoju,Thomas Weber,Andrea Lovera,Oksana Shvydkiv,Martin Roth,Anne-Sophie Munser

doi:10.1063/1.5013325

Abstract

In order to leverage the immense potential of droplet microfluidics, it is necessary to simplify the process of chip design and fabrication. While polydimethylsiloxane (PDMS) replica molding has greatly revolutionized the chip-production process, its dependence on 2D-limited photolithography has restricted the design possibilities, as well as further dissemination of microfluidics to non-specialized labs. To break free from these restrictions while keeping fabrication straighforward, we introduce an approach to produce complex multi-height (3D) droplet microfluidic glass molds and subsequent chip production by PDMS replica molding. The glass molds are fabricated with sub-micrometric resolution using femtosecond laser machining technology, which allows directly realizing designs with multiple levels or even continuously changing heights. The presented technique significantly expands the experimental capabilities of the droplet microfluidic chip. It allows direct fabrication of multilevel structures such as droplet traps for prolonged observation and optical fiber integration for fluorescence detection. Furthermore, the fabrication of novel structures based on sloped channels (ramps) enables improved droplet reinjection and picoinjection or even a multi-parallelized drop generator based on gradients of confinement. The fabrication of these and other 3D-features is currently only available at such resolution by the presented strategy. Together with the simplicity of PDMS replica molding, this provides an accessible solution for both specialized and non-specialized labs to customize microfluidic experimentation and expand their possibilities.

Highlights

In order to leverage the immense potential of droplet microfluidics, it is necessary to simplify the process of chip design and fabrication
To break free from these restrictions while keeping fabrication straighforward, we introduce an approach to produce complex multi-height (3D) droplet microfluidic glass molds and subsequent chip production by PDMS replica molding
The glass molds are fabricated with sub-micrometric resolution using femtosecond laser machining technology, which allows directly realizing designs with multiple levels or even continuously changing heights

Summary

Introduction

It does not require clean-room facilities, can be automated, and provides flexibility to obtain 3D structures without significant increase in fabrication complexity and time.[22] It offers the crucial advantages of achieving sub-micrometric resolution and that can be applied in different materials,[23] but most prominently in glass. A comparatively simple and effective solution is to use the advantages of 3D-prototyping to create molds that can be subsequently casted in PDMS.[28,29] This enables the production of structures with sub-micrometer resolution, high aspect ratios, and the straightforward production of pseudo-3D-features. This could prove specially relevant in the particular case of droplet microfluidics, where the rapidly growing number of non-microfluidic adopters require the flexibility to fabricate chips that fulfill innovative applications. We demonstrate the applications of high resolution molds in channels with changing depth, stable picoinjection, detection with optical fibers, and ultra-fast droplet generation using confinement gradients

Methods

Results

Conclusion