SmartTags: IoT Product Passport for Circular Economy Based on Printed Sensors and Unique Item-Level Identifiers.

In this paper, we present a method that facilitates Internet of Things (IoT) for building a product passport and data exchange enabling the next stage of the circular economy. SmartTags based on printed sensors (i.e., using functional ink) and a modified GS1 barcode standard enable unique identification of objects on a per item-level (including Fast-Moving Consumer Goods-FMCG), collecting, sensing, and reading of parameters from environment as well as tracking a products' lifecycle. The developed ontology is the first effort to define a semantic model for dynamic sensors, including datamatrix and QR codes. The evaluation of decoding and readability of identifiers (QR codes) showed good performance for detection of sensor state printed over and outside the QR code data matrix, i.e., the recognition ability with image vision algorithm was possible. The evaluation of the decoding performance of the QR code data matrix printed with sensors was also efficient, i.e., the QR code ability to be decoded with the reader after reversible and irreversible process of ink (dis)appearing was preserved, with slight drop in performance if ink density is low.

One-Step Microfluidic Fabrication of Polyelectrolyte Microcapsules in Aqueous Conditions for Protein Release.

We report a microfluidic approach for one-step fabrication of polyelectrolyte microcapsules in aqueous conditions. Using two immiscible aqueous polymer solutions, we generate transient water-in-water-in-water double emulsion droplets and use them as templates to fabricate polyelectrolyte microcapsules. The capsule shell is formed by the complexation of oppositely charged polyelectrolytes at the immiscible interface. We find that attractive electrostatic interactions can significantly prolong the release of charged molecules. Moreover, we demonstrate the application of these microcapsules in encapsulation and release of proteins without impairing their biological activities. Our platform should benefit a wide range of applications that require encapsulation and sustained release of molecules in aqueous environments.

Vesicles-on-a-chip: A universal microfluidic platform for the assembly of liposomes and polymersomes.

In this study, we present a PDMS-based microfluidic platform for the fabrication of both liposomes and polymersomes. Based on a double-emulsion template formed in flow-focusing configuration, monodisperse liposomes and polymersomes are produced in a controlled manner after solvent extraction. Both types of vesicles can be formed from the exact same combination of fluids and are stable for at least three months under ambient storage conditions. By tuning the flow rates of the different fluid phases in the flow-focusing microfluidic design, the size of the liposomes and polymersomes can be varied over at least one order of magnitude. This method offers a versatile tool for future studies, e.g., involving the encapsulation of biological agents and the functionalization of artificial cell membranes, and might also be applicable for the controlled fabrication of hybrid vesicles.

Monitoring reactive microencapsulation dynamics using microfluidics.

We use microfluidic polydimethylsiloxane (PDMS) devices to measure the kinetics of reactive encapsulations occurring at the interface of emulsion droplets. The formation of the polymeric shell is inferred from the droplet deformability measured in a series of expansion-constriction chambers along the microfluidic chip. With this tool we quantify the kinetic processes governing the encapsulation at the very early stage of shell formation with a time resolution of the order of the millisecond for overall reactions occurring in less than 0.5 s. We perform a comparison of monomer reactivities used for the encapsulation. We study the formation of polyurea microcapsules (PUMCs); the shell formation proceeds at the water-oil interface by an immediate reaction of amines dissolved in the aqueous phase and isocyanates dissolved in the oil phase. We observe that both monomers contribute differently to the encapsulation kinetics. The kinetics of the shell formation process at the oil-in-water (O/W) experiments significantly differs from the water-in-oil (W/O) systems; the component dissolved in the continuous phase has the largest impact on the kinetics. In addition, we quantified the retarding effect on the encapsulation kinetics by the interface stabilizing agent (surfactant). Our approach is valuable for quantifying in situ reactive encapsulation processes and provides guidelines to generate microcapsules with soft interfaces of tailored and controllable interfacial properties.

Polyurea microcapsules in microfluidics: surfactant control of soft membranes.

Interfacial polymerization techniques offer a versatile route for microcapsule synthesis. We designed a microfluidic process to synthesize monodisperse polyurea microcapsules (PUMCs); the microcapsules are formed by an interfacial polymerization of isocyanate dissolved in the oil and an amine dissolved in water. We measure the mechanical properties of the capsule as well as transport properties through the membrane using two microfluidic methods. We show that the elasticity and the permeability of the shell are controlled by surfactant additives, added during the synthesis. The control of the nanostructure of the shell by surfactants provides new means to design encapsulation systems with tailored mechanical and physicochemical properties.

Controlling the morphology of polyurea microcapsules using microfluidics.

We use microfluidics to continuously produce monodisperse polyurea microcapsules (PUMCs) having either aqueous or nonaqueous cores. The microcapsule shells are formed by the reaction between an isocyanate, dissolved in oil, and an amine, dissolved in water, at the surface of oil-in-water or water-in-oil drops immediately as they are formed. Different microcapsule morphologies can be generated using our approach. The thickness of the microcapsule shell increases with an increase in the amine solubility in the oil; this finding provides a simple mechanism by which the PUMC shell thickness can be controlled.