Toward Wearable Sensors: Fluorescent Attoreactor Mats as Optically Encoded Cross-Reactive Sensor Arrays

A Diverse Micromorphology of Photonic Crystal Chips for Multianalyte Sensing

The diversity by nano/microstructural material or device constructing can provide the exciting opportunity for sensitivity and selectivity to achieve facile and efficient multianalyte recognition for clinical diagnosis, environment monitoring, etc., in complex system analysis. Colloidal poly(styrene-methyl methacrylate-acrylic acid) (poly(St-MMA-AA)) nanoparticle-assembled photonic crystals (PCs) can achieve manipulative 3D structural colors and approach PC sensor chip for high-efficient multianalysis utilizing simple dye. Focusing on the morphology effects of structural color, a PC microchip is designed and constructed with various geometrical micromorphologies. Based on the angle dependence of colloidal-crystal structural color, the stopband distribution is explored on various morphological PC pixels. Selective fluorescent enhancement is realized for stopband-matched PCs, which approach the successful discrimination of metal ions and complex multianalysis of groundwater. Meanwhile, printed droplet-shaping manipulation can achieve a large-scale structural-color sensor array of chips with designable nano/microstructures via colloidal assembly. It will be the critical puzzle piece between macromorphology and microstructure for the structural-color researches.

Soft and flexible material-based affinity sensors

Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field.

A Minimalist Approach for Distinguishing Individual Lanthanide Ions Using Multivariate Pattern Analysis

To discriminate among the 14 trivalent lanthanide ions, curcumin, a naturally occurring, nontoxic, off-the-shelf, commercially available compound containing a single fluorophore, was chosen as a probe in the water media at pH 6.8 and pH 8.2. By measuring the emission and absorption spectra of the probe, under the different pH conditions, and by performing linear discriminant analysis on the data, 14 Ln³⁺ ions were discriminated. Additionally, an easy tool for the nonspecialists was developed with easily available household substances, using a smartphone app, which added an extra advantage to this single probe. This probe possesses advantageous features in terms of low-cost and instant on-site detection of the lanthanide ions.

Spider-web inspired multi-resolution graphene tactile sensor

Inspired by discrepant microstructures of spider web, a multi-resolution tactile sensor was printed with integrating different structures graphene.

Towards maintenance-free biosensors for hundreds of bind/release cycles

A single aptamer bioreceptor layer was formed using a common streptavidin-biotin immobilization strategy and employed for 100-365 bind/release cycles. Chemically induced aptamer unfolding and release of its bound target was accomplished using alkaline solutions with high salt concentrations or deionized (DI) water. The use of DI water scavenged from the ambient atmosphere represents a first step towards maintenance-free biosensors that do not require the storage of liquid reagents. The aptamer binding affinity was determined by surface plasmon resonance and found to be almost constant over 100-365 bind/release cycles with a variation of less than 5% relative standard deviation. This reversible operation of biosensors based on immobilized aptamers without storage of liquid reagents introduces a conceptually new perspective in biosensing. Such new biosensing capability will be important for distributed sensor networks, sensors in resource-limited settings, and wearable sensor applications.