Liquid–liquid phase separation (LLPS) in biology is a recently appreciated means of intracellular compartmentalization. Because the mechanisms driving phase separations are grounded in physical interactions, they can be recreated within less complex systems consisting of only a few simple components, to serve as artificial microcompartments. Within these simple systems, the effect of compartmentalization and microenvironments upon biological reactions and processes can be studied. This review will explore several approaches to incorporating LLPS as artificial cytoplasms and in artificial cells, including both segregative and associative phase separation.

The interaction between water and surfaces is observed in our daily lives and is used in laboratories to study materials properties, such as interfacial tension. Making the connection between fundamental scientific phenomena and everyday observations is a powerful method of highlighting the importance and relevance of science to the K−12 population. Typically, expensive equipment, such as dedicated contact angle goniometers, is used in laboratories to observe how water interacts with materials. Obtaining such laboratory-grade equipment for the K−12 classroom is not only difficult but also unnecessary. Thus, we present an affordable 3D printed setup for the reliable measurement of the contact angle of water on a variety of natural and synthetic surfaces, using smart devices (e.g., cell phone, tablet) as the imaging basis. This setup enables proper backlighting, a stable camera holder for quality images, and a flat surface with an easily adjustable platform to hold the sample. Compared to simply holding the smart device by hand, the 3D printed method provided better quality images and an improved data acquisition experience when measuring the contact angle. Use in a middle school setting has shown that this 3D printed method is successful for teaching about water/surface interactions on both hydrophilic and hydrophobic surfaces. This method can easily be adapted to suit learning objectives, allowing educators to explore a range of hydrophobic and hydrophilic surfaces of both biological and synthetic origin.

The use of aqueous polymer-based phase separation within water-in-oil emulsion droplets provides a powerful platform for exploring the impact of compartmentalization and preferential partitioning on biologically relevant solutes. By forming an emulsion, a bulk solution is converted into a large number of chemically isolated microscale droplets. Microfluidic techniques provide an additional level of control over the formation of such systems. This enables the selective production of multiphase droplets with desired solution compositions and specific characteristics, such as solute partitioning. Here, we demonstrate control over the chemical microenvironment by adjusting the composition to increase tie line length for poly­(ethylene glycol) (PEG)-dextran aqueous two-phase systems (ATPS) encapsulated within multiphase water-in-fluorocarbon oil emulsion droplets. Through rational adjustment of microfluidic parameters alone, ATPS droplets containing differing compositions could be produced during the course of a single experiment, with the produced droplets demonstrating a controllable range of tie line lengths. This provided control over partitioning behavior for biologically relevant macromolecules such that the difference in local protein concentration between adjacent phases could be rationally tuned. This work illustrates a broadly applicable technique to rationally create emulsified multiphase aqueous systems of desired compositions through the adjustment of microfluidic parameters alone, allowing for easy and rapid screening of various chemical microenvironments.