Conformal Volumetric Grayscale Metamaterials.

Conformal artificial electromagnetic media that feature tailorable responses as a function of incidence wavelength and angle represent universal components for optical engineering. Conformal grayscale metamaterials are introduced as a new class of volumetric electromagnetic media capable of supporting highly multiplexed responses and arbitrary, curvilinear form factors. Subwavelength-scale voxels based on irregular shapes are designed to accommodate a continuum of dielectric values, enabling the freeform design process to reliably converge to exceptionally high figures of merit (FOMs) for a given multi-objective design problem. Through additive manufacturing of ceramic-polymer composites, microwave metamaterials, designed for the radio-frequency range of 8-12 GHz, are experimentally fabricated and devices with extreme dispersion profiles, an airfoil-shaped beam-steering device, and a broadband, broad-angle conformal carpet cloak, are demonstrated. It is anticipated that conformal volumetric metamaterials will lead to new classes of compact and multifunctional imaging, sensing, and communications systems.

Photonic crystal enhanced fluorescence emission and blinking suppression for single quantum dot digital resolution biosensing.

While nanoscale quantum emitters are effective tags for measuring biomolecular interactions, their utilities for applications that demand single-unit observations are limited by the requirements for large numerical aperture (NA) objectives, fluorescence intermittency, and poor photon collection efficiency resulted from omnidirectional emission. Here, we report a nearly 3000-fold signal enhancement achieved through multiplicative effects of enhanced excitation, highly directional extraction, quantum efficiency improvement, and blinking suppression through a photonic crystal (PC) surface. The approach achieves single quantum dot (QD) sensitivity with high signal-to-noise ratio, even when using a low-NA lens and an inexpensive optical setup. The blinking suppression capability of the PC improves the QDs on-time from 15% to 85% ameliorating signal intermittency. We developed an assay for cancer-associated miRNA biomarkers with single-molecule resolution, single-base mutation selectivity, and 10-attomolar detection limit. Additionally, we observed differential surface motion trajectories of QDs when their surface attachment stringency is altered by changing a single base in a cancer-specific miRNA sequence.

WeChat-based remote follow-up management alleviates the home care burden and anxiety of parents of premature infants: Randomized controlled study.

OBJECTIVE: The purpose of this study was to explore the effect of WeChat-based remote follow-up management on reducing the home care burden and anxiety of parents of premature infants. METHODS: A randomized controlled study was conducted in our hospital, with 150 premature infants enrolled in this study, each with 75 cases in the intervention group and the control group. WeChat-based remote follow-up management was performed in the intervention group after discharge, while traditional outpatient follow-up management was performed in the control group. Zarit Burden Interview (ZBI) scale as the primary outcome was used to compare the parental care burden between the two groups. RESULTS: At the 1-month follow-up, the ZBI (37.1 ± 8.3 vs. 54.2 ± 10.5 [mean ± SD], mean difference: 17.1, the 95% confidence interval for the mean difference: [14.07, 20.13], P = 0.016), Family Caregiver Task Inventory (FCTI) scale (23.1 ± 5.2 vs. 33.4 ± 6.7 [mean ± SD], mean difference: 10.3, the 95% confidence interval for the mean difference: [8.38, 12.22], P = 0.023), Self-Rating Anxiety Scale (SAS) (49.6 ± 8.5 vs. 60.2 ± 10.8 [mean ± SD], mean difference: 10.6, the 95% confidence interval for the mean difference: [7.49,13.71], P = 0.021) and Self-Rating Depression Scale (SDS) (48.2 ± 9.5 vs. 58.8 ± 11.2 [mean ± SD], mean difference: 10.6, the 95% confidence interval for the mean difference: [7.28, 13.92], P = 0.019) scores of the intervention group were lower than those of the control group, and the lower scores indicate better outcomes. CONCLUSION: WeChat-based remote follow-up management of premature infants after discharge can effectively improve parents' ability to care and their psychological state and reduce burden of care.

Photonic resonator interferometric scattering microscopy.

Interferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the <1% transmitted light to create a large intensity contrast. Importantly, the scattered photons assume the wavevectors delineated by PC's photonic band structure, resulting in the ability to utilize a non-immersion objective without significant loss at illumination density as low as 25 W cm-2. An analytical model of the scattering process is discussed, followed by demonstration of virus and protein detection. The results showcase the promise of nanophotonic surfaces in the development of resonance-enhanced interferometric microscopies.

Critical Review: digital resolution biomolecular sensing for diagnostics and life science research.

One of the frontiers in the field of biosensors is the ability to quantify specific target molecules with enough precision to count individual units in a test sample, and to observe the characteristics of individual biomolecular interactions. Technologies that enable observation of molecules with "digital precision" have applications for in vitro diagnostics with ultra-sensitive limits of detection, characterization of biomolecular binding kinetics with a greater degree of precision, and gaining deeper insights into biological processes through quantification of molecules in complex specimens that would otherwise be unobservable. In this review, we seek to capture the current state-of-the-art in the field of digital resolution biosensing. We describe the capabilities of commercially available technology platforms, as well as capabilities that have been described in published literature. We highlight approaches that utilize enzymatic amplification, nanoparticle tags, chemical tags, as well as label-free biosensing methods.

Activate capture and digital counting (AC + DC) assay for protein biomarker detection integrated with a self-powered microfluidic cartridge.

We demonstrate a rapid, 2-step, and ultrasensitive assay approach for quantification of target protein molecules from a single droplet test sample. The assay is comprised of antibody-conjugated gold nanoparticles (AuNPs) that are "activated" when they are mixed with the test sample and bind their targets. The resulting liquid is passed through a microfluidic channel with a photonic crystal (PC) biosensor that is functionalized with secondary antibodies to the target biomarker, so that only activated AuNPs are captured. Utilizing recently demonstrated hybrid optical coupling between the plasmon resonance of the AuNP and the resonance of the PC, each captured AuNP efficiently quenches the resonant reflection of the PC, thus enabling the captured AuNPs to be digitally counted with high signal-to-noise. To achieve a 2-step assay process that is performed on a single droplet test sample without washing steps or active pump elements, controlled single-pass flow rate is obtained with an absorbing paper pad waste reservoir embedded in a microfluidic cartridge. We use the activate capture and digital counting (AC + DC) approach to demonstrate HIV-1 capsid antigen p24 detection from a 40 µL spiked-in human serum sample at a one thousand-fold dynamic range (1-103 pg mL-1) with only a 35-minute process that is compatible with point-of-care (POC) analysis. The AC + DC approach allows for ultrasensitive and ultrafast biomolecule detection, with potential applications in infectious disease diagnostics and early stage disease monitoring.

Microcavity-Mediated Spectrally Tunable Amplification of Absorption in Plasmonic Nanoantennas.

Nanoantenna-microcavity hybrid systems offer unique platforms for the study and manipulation of light at the nanoscale, since their constituents have either low mode volume or long photon storage time. A nearby dielectric optical cavity can modify the photonic environment surrounding a plasmonic nanoantenna, presenting opportunities to sculpt its spectral response. However, matching the polar opposites for enhanced light-matter interactions remains challenging, as the antenna can be rendered transparent by the cavity through destructive Fano interferences. In this work, we tackle this issue by offering a new plasmonic-photonic interaction framework. By coupling to a photonic crystal guided resonance, a gold nanostar delivers 1 order of magnitude amplified absorption, and the ultrasharp Lorentzian-line-shaped hybrid resonance is continuously tunable over a broad spectral range by scanning of the incidence angle. Our intuitive coupled mode model reveals that a distinct optical pathway highlighting the cavity-mediated activation of nanoantennas is key for absorption enhancement. Moreover, we show that the line width of the enhancement can be widely tunable, and that the maximum power transferred to the antennas is attained under critical coupling. The cooperative hybrid system opens up new opportunities to boost a wealth of applications including ultrasensitive molecular spectroscopy, plasmonic hot carrier chemistry, thermoplasmonic, spontaneous emission enhancement, nanolasers, and many more.

Design of anapole mode electromagnetic field enhancement structures for biosensing applications.

The design of an all-dielectric nanoantenna based on nonradiating "anapole" modes is studied for biosensing applications in an aqueous environment, using FDTD electromagnetic simulation. The strictly confined electromagnetic field within a circular or rectangular opening at the center of a cylindrical silicon disk produces a single point electromagnetic hotspot with up to 6.5x enhancement of |E|, for the 630-650 nm wavelength range, and we can increase the value up to 25x by coupling additional electromagnetic energy from an underlying PEC-backed substrate. We characterize the effects of the substrate design and slot dimensions on the field enhancement magnitude, for devices operating in a water medium.

An Automated Microfluidic Assay for Photonic Crystal Enhanced Detection and Analysis of an Antiviral Antibody Cancer Biomarker in Serum.

We report on the implementation of an automated platform for detecting the presence of an antibody biomarker for human papillomavirus-associated oropharyngeal cancer from a single droplet of serum, in which a nanostructured photonic crystal surface is used to amplify the output of a fluorescence-linked immunosorbent assay. The platform is comprised of a microfluidic cartridge with integrated photonic crystal chips that interfaces with an assay instrument that automates the introduction of reagents, wash steps, and surface drying. Upon assay completion, the cartridge interfaces with a custom laser-scanning instrument that couples light into the photonic crystal at the optimal resonance condition for fluorescence enhancement. The instrument is used to measure the fluorescence intensity values of microarray spots corresponding to the biomarkers of interest, in addition to several experimental controls that verify correct functioning of the assay protocol. In this work, we report both dose-response characterization of the system using anti-E7 antibody introduced at known concentrations into serum and characterization of a set of clinical samples from which results were compared with a conventional enzyme-linked immunosorbent assay (ELISA) performed in microplate format. The demonstrated capability represents a simple, rapid, automated, and high-sensitivity method for multiplexed detection of protein biomarkers from a low-volume test sample.

Nanoantenna-Microcavity Hybrids with Highly Cooperative Plasmonic-Photonic Coupling.

Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna-cavity coupling approach using a Fabry-Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light-matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies.

Porous photonic crystal external cavity laser biosensor.

We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO2 dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

The rational design of inhibitors of nitric oxide formation by inducible nitric oxide synthase.

A series of compounds was rationally designed as inhibitors of dimer formation of the inducible isoform of nitric oxide synthase, and subsequent nitric oxide production. The conformation of two fragments obtained from a crystal structure was utilized to design a tether connecting those same two fragments. The resulting compounds were potent dimerization inhibitors that bound to the enzyme in a similar conformation as the fragments.

Covalently bound hole-injecting nanostructures. Systematics of molecular architecture, thickness, saturation, and electron-blocking characteristics on organic light-emitting diode luminance, turn-on voltage, and quantum efficiency.

Hole transporting materials are widely used in multilayer organic and polymer light-emitting diodes (OLEDs, PLEDs, respectively) and are indispensable if device electroluminescent response and durability are to be truly optimized. This contribution analyzes the relative effects of tin-doped indium oxide (ITO) anode-hole transporting layer (HTL) contact versus the intrinsic HTL materials properties on OLED performance. Two siloxane-based HTL materials, N,N'-bis(p-trichlorosilylpropyl)-naphthalen-1-yl)-N,N'-diphenyl-biphenyl-4,4'-diamine (NPB-Si(2)) and 4,4'-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si(2)), are designed and synthesized. They have the same hole transporting triarylamine cores as conventional HTL materials such as 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) and N,N-diphenyl-N,N-bis(3-methylphenyl)-1,1-biphenyl)-4,4-diamine (TPD), respectively. However, they covalently bind to the ITO anode, forming anode-HTL contacts that are intrinsically different from those of the anode to TPD and NPB. Applied to archetypical tris(8-hydroxyquinolato)aluminum(III) (Alq)-based OLEDs as (1) the sole HTLs or (2) anode-NPB HTL interlayers, NPB-Si(2) and TPD-Si(2) enhance device electroluminescent response significantly versus comparable devices based on NPB alone. In the first case, OLEDs with 36 000 cd/m(2) luminance, 1.6% forward external quantum efficiency (eta(ext)), and 5 V turn-on voltages are achieved, affording a 250% increase in luminance and approximately 50% reduction in turn-on voltage, as compared to NPB-based devices. In the second case, even more dramatic enhancement is observed (64 000 cd/m(2) luminance; 2.3% eta(ext); turn-on voltages as low as 3.5 V). The importance of the anode-HTL material contact is further explored by replacing NPB with saturated hydrocarbon siloxane monolayers that covalently bind to the anode, without sacrificing device performance (30 000 cd/m(2) luminance; 2.0% eta(ext); 4.0 V turn-on voltage). These results suggest new strategies for developing OLED hole transporting structures.

Molecularly "engineered" anode adsorbates for probing OLED interfacial structure-charge injection/luminance relationships: large, structure-dependent effects.

Molecule-scale structure effects at organic light-emitting diodes (OLED) anode-organic transport layer interfaces are probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine molecules differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure, charge injection and electroluminescence properties. Dramatic variations in hole injection magnitude and OLED performance can be correlated with the molecular structures and electrochemically derived heterogeneous electron-transfer rates of such triarylamine fragments, placed precisely at the anode-hole transport layer interface. Very bright and efficient ( approximately 70 000 cd/m2 and approximately 2.5% forward external quantum efficiency) OLEDs have thereby been fabricated.