Crystallization at droplet interfaces for the fabrication of geometrically programmed synthetic magnetosomes.

Biological systems demonstrate exquisite three dimensional (3D) control over crystal nucleation and growth using soft micro/nanoenvironments, such as vesicles, for reagent transport and confinement. It remains challenging to mimic such biomineralization processes using synthetic systems. A synthetic mineralization strategy applicable to the synthesis of artificial magnetosomes with programmable magnetic domains is described. This strategy relies on the compartmentalization of precursors in surfactant-stabilized liquid microdroplets which, when contacted, spontaneously form lipid bilayers that support reagent transport and interface-confined magnetite nucleation and growth. The resulting magnetic domains are polarized and thus readily manipulated using magnetic fields or assembled using droplet-droplet interactions. This strategy presents a new, liquid phase procedure for the synthesis of vesicles with geometrically controlled inorganic features that would be difficult to produce otherwise. The artificial magnetosomes demonstrated could find use in, for example, drug/cargo delivery, droplet microfluidics, and formulation science.

Mechanically Induced Hydrophobic Recovery of Poly(dimethylsiloxane) (PDMS) for the Generation of Surfaces with Patterned Wettability.

Silicone elastomers are used in a variety of "stretchable" technologies (e.g., wearable electronics and soft robotics) that require the elastomeric components to accommodate varying magnitudes of mechanical stress during operation; however, there is limited understanding of how mechanical stress influences the surface chemistry of these elastomeric components despite the potential importance of this property with regards to overall function. In this study, plasma-oxidized silicone (poly(dimethylsiloxane)) films were systematically subjected to various amounts of tensile stress and the resulting surface chemical changes were monitored using contact angle measurements, X-ray photoelectron spectroscopy, and gas chromatography-mass spectrometry. Understanding the influence of mechanical stress on these materials made possible the development of a facile method for the rapid, on-demand switching of surface wettability and the generation of surface wettability patterns and gradients. The use of mechanical stress to control surface wettability is broadly applicable to the fields of microfluidics, soft robotics, printing, and to the design of adaptable materials and sensors.

Reconfigurable microfluidic systems with reversible seals compatible with 2D and 3D surfaces of arbitrary chemical composition.

Microfluidic channels are typically fabricated in polydimethylsiloxane (PDMS) using soft lithography and sealed against a support substrate using various irreversible/reversible techniques-the most widely used method is the irreversible bonding of PDMS to glass using oxygen plasma. These techniques are limited in their ability to seal channels against rough, uneven, and/or three-dimensional substrates. This manuscript describes the design and fabrication of soft microfluidic systems from combinations of silicone elastomers that can be reversibly sealed against an array of materials of various topographies/geometries using compression. These soft systems have channels with cross-sectional dimensions that can be decreased, reversibly, by hundreds of microns using compressive stress, and the ability to interface with virtually any support substrate. These capabilities go beyond that achievable with devices fabricated in PDMS alone and enable the integration of microfluidic functionality directly with rough and/or 3D surfaces, providing new opportunities in solution processing useful to, for example, materials science and the analytical/forensic sciences.