Direct electrification of silicon microfluidics for electric field applications

Abstract

Microfluidic systems are widely used in fundamental research and industrial applications due to their unique behavior, enhanced control, and manipulation opportunities of liquids in constrained geometries. In micrometer-sized channels, electric fields are efficient mechanisms for manipulating liquids, leading to deflection, injection, poration or electrochemical modification of cells and droplets. While PDMS-based microfluidic devices are used due to their inexpensive fabrication, they are limited in terms of electrode integration. Using silicon as the channel material, microfabrication techniques can be used to create nearby electrodes. Despite the advantages that silicon provides, its opacity has prevented its usage in most important microfluidic applications that need optical access. To overcome this barrier, silicon-on-insulator technology in microfluidics is introduced to create optical viewports and channel-interfacing electrodes. More specifically, the microfluidic channel walls are directly electrified via selective, nanoscale etching to introduce insulation segments inside the silicon device layer, thereby achieving the most homogeneous electric field distributions and lowest operation voltages feasible across microfluidic channels. These ideal electrostatic conditions enable a drastic energy reduction, as effectively shown via picoinjection and fluorescence-activated droplet sorting applications at voltages below 6 and 15 V, respectively, facilitating low-voltage electric field applications in next-generation microfluidics.

Silicon-Based 3D Microfluidics for Parallelization of Droplet Generation

“…Further, it makes devices reusable as they can be cleaned under harsh conditions. Moreover, silicon technology enables a scalable, high-density integration of other functionalities such as channel-nearby electrodes that are not feasible using other technologies [ 47 ], sensing components, optoelectronic components, including laser sources and photodetectors, that can all be seamlessly and monolithically integrated in silicon. This setting will pave the road towards numerous novel applications in fundamental research, chemistry, healthcare and life sciences or pharmaceutical production.…”

Additiv gefertigte Reservoirs für mikrofluidische Chips/Additively manufactured on-chip reservoirs as an interface to microfluidic microchips

“…Dabei sind sie omnipräsent: In haushaltsüblichen Tintenstrahldruckern vereinen sie seit der Millenniumwende die Hauptfunktionen des Druckkopfs (Mikrokanäle, Tintenausstoßaktorik und Ausstoßdüsen) in einer hochminiaturisierten Einheit [1,2]. Gegenüber polymerbasierten Chips, ermöglicht monokristallines Silizium inhärent die monolithische Integration von elektronischen, mechanischen und fluidischen Komponenten [3,4].…”