Thermoelectric Manipulation of Aqueous Droplets in Microfluidic Devices

Abstract

This paper describes a method for manipulating the temperature inside aqueous droplets, utilizing a thermoelectric cooler to control the temperature of select portions of a microfluidic chip. To illustrate the adaptability of this approach, we have generated an "ice valve" to stop fluid flow in a microchannel. By taking advantage of the vastly different freezing points for aqueous solutions and immiscible oils, we froze a stream of aqueous droplets that were formed on-chip. By integrating this technique with cell encapsulation into aqueous droplets, we were also able to freeze single cells encased in flowing droplets. Using a live-dead stain, we confirmed the viability of cells was not adversely affected by the process of freezing in aqueous droplets provided cryoprotectants were utilized. When combined with current droplet methodologies, this technology has the potential to both selectively heat and cool portions of a chip for a variety of droplet-related applications, such as freezing, temperature cycling, sample archiving, and controlling reaction kinetics.

Droplet microfluidic technology for single-cell high-throughput screening

“…Previously, important steps have been made to develop specific components required to perform droplet-based manipulations, including cell encapsulation (2)(3)(4)(5)(6)(7)(8), droplet merging (9-13), droplet mixing (14,15), on-chip incubation (16), droplet sorting (17), and introduction of multiple compounds (18). However, each of these droplet manipulations has been demonstrated as separate modules that have not been assembled into an integrated biological assay.…”

The Dropletisation of Bio-Reactions

“…A droplet-based system provides the best format for true m-TAS as droplets can be manipulated in a number of ways with ease. Through the use of electrodes the path of droplet travel can be directed allowing for the splitting [41][42][43], merging [44][45][46][47][48], sorting [42,47,[49][50][51] and storage [52][53][54][55][56] of droplets on the device. For example, known quantities of reagents can be added to each sample through the precise merging of reagent-containing and samplecontaining droplets [48].…”

Mikrotröpfchen in Mikrofluidiksystemen: eine Technik für Entdeckungen in der Chemie und Biologie

“…Bei Zusatz eines Frostschutzmittels waren Maus-B-Lymphocyten in gefrorenen Tröpfchen auch nach einwöchiger Lagerung noch lebensfähig. [154] 6. In-vitro-Transkription und -Translation Die Aufspaltung einer Population in ihre Mitglieder mit anschließendem Einschluss in Mikrotröpfchen kann für den Aufbau von Bibliotheken genutzt werden.…”