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This review highlights key development of point-of-care diagnostics for detecting DNA, proteins, bacteria/pathogens, and other species in samples that can be used for diagnosing disease and detecting harmful chemical and biochemical contaminants in samples. These technologies have great promise for improving the quality of life for those in the developing world.

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Stretchable poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-10% AAc) microgel-based reservoir devices were fabricated and used to control the release rate of the small molecule model drug tris(4-(dimethylamino)phenyl)methylium chloride (crystal violet, CV) to solution by varying the Au layer thickness coating the microgels and device elongation. Specifically, we showed that CV could be loaded into the microgel layer of the devices via electrostatic interactions at pH 6.5, and the release could be triggered upon exposure to a pH 3.0 solution, which breaks the microgel−CV electrostatic interactions. We demonstrated that the rate of release could be increased by decreasing the Au layer thickness coating microgels and by stretching, that is, thin Au and high elongation promoted the relatively fast release of CV from the device. We found that the Au overlayer thickness (and porosity) dominated the observed release rate profiles when the device was not stretched (or at low elongation), while elongation-induced cracks dominated the release rate at high elongation. We also showed that the CV release kinetics could transition from low ("off") to high ("on"), which enhanced when the devices are stretched. This behavior could be exploited in the future for autonomous release systems that release small molecules when stretched by natural processes, for example, movement of joints and muscles.

Light-and temperature-responsive poly(N-isopropylacrylamide-co-nitrobenzyl methacrylate) (pNIPAm-co-NBMA) microgels were synthesized via free-radical precipitation polymerization and exhibited a hydrodynamic diameter of 320 ± 40 nm. We demonstrated that the microgels' NMBA groups were cleaved upon UV irradiation, which we showed could be used for lightactivated release of fluorescein (used as a model drug molecule). Moreover, drug release could also be promoted by microgel deswelling due to heating. Specifically, the hydrophobic model drug fluorescein was incorporated into the pNIPAm-co-NBMA microgels via physical interactions, and we showed that exposure to UV light (or heating) could induce its release. Thus, the pNIPAmco-NBMA microgels could find the use for applications requiring triggered release of cargo when needed.

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