Lubricated Surface in a Vertical Double-Sided Architecture for Radiative Cooling and Atmospheric Water Harvesting.

Radiative cooling significantly lowers condenser temperatures below ambient levels, enabling atmospheric water harvesting (AWH) without additional energy. However, traditional sky-facing condensers have low cooling power density, and water droplets remain pinned on surface, requiring active condensate collection. To overcome these challenges, a lubricated surface (LS) coating-consisting of highly scalable polydimethylsiloxane elastomer lubricated with silicone oil-is introduced on the condenser side in a vertical double-sided architecture. The design not only effectively doubles the local cooling power, but also eliminates contact-line pinning, enabling passive, gravity-driven collection of water. Robust AWH is demonstrated from a 30 × 30 cm2 sample in outdoor environments (of varying humidity levels and wind speeds in different months) and with no artificial flow of humidified air. In one outdoor test, the passive water collection rate of LS coating reaches 21 g m-2 h-1 double that on superhydrophobic surface, 10 g m-2 h-1. In indoor testing (20 °C and 80% relative humidity), this system achieves a condensation rate ≈87% of the theoretical limit with up to 90% of the total condensate passively collected. this approach achieves effective AWH in a decentralized approach that removes the need for piping infrastructure and external energy input.

A solar-driven atmospheric water extractor for off-grid freshwater generation and irrigation.

Solar-driven atmospheric water extraction (SAWE) is a sustainable technology for decentralized freshwater supply. However, most SAWE systems produce water intermittently due to the cyclic nature, with adoption hindered by complex design requirements or periodic manual operations. Herein, a fully passive SAWE system that can continuously produce freshwater under sunlight is presented. By optimizing the three-dimensional architecture to facilitate spontaneous mass transport and efficient energy utilization, this system can consistently produce 0.65 L m-2 h-1 of freshwater under 1-sun illumination at 90% relative humidity (RH) and functions in arid environments with an RH as low as 40%. We test the practical performance of a scaled-up system in Thuwal, Saudi Arabia over 35 days across two seasons. The system produces 2.0-3.0 L m-2 per day of freshwater during the summer and 1.0-2.8 L m-2 per day of freshwater during the fall, without requiring additional maintenance. Intriguingly, we demonstrate the system's potential for off-grid irrigation by successfully growing cabbage plants using atmospheric water. This passive SAWE system, harnessing solar energy to continuously extract moisture from air for drinking and irrigation, offers a promising solution to address the intertwined challenges of energy, water, and food supply, particularly for remote and water-scarce regions.

Solar-Powered Gram-Scale Ammonia Production from Nitrate.

The photoelectrochemical (PEC) method has the potential to be an attractive route for converting and storing solar energy as chemical bonds. In this study, a maximum NH3 production yield of 1.01 g L-1 with a solar-to-ammonia conversion efficiency of 8.17% through the photovoltaic electrocatalytic (PV-EC) nitrate (NO3 -) reduction reaction (NO3 -RR) is achieved, using silicon heterojunction solar cell technology. Additionally, the effect of tuning the operation potential of the PV-EC system and its influence on product selectivity are systematically investigated. By using this unique external resistance tuning approach in the PV-EC system, ammonia production through nitrate reduction performance from 96 to 360 mg L-1 is enhanced, a four-fold increase. Furthermore, the NH3 is extracted as NH4Cl powder using acid stripping, which is essential for storing chemical energy. This work demonstrates the possibility of tuning product selectivity in PV-EC systems, with prospects toward pilot scale on value-added product synthesis.

A robust thin-film droplet-induced electricity generator.

The pursuit of cost-effective, high-voltage electricity generators activated by droplets represents a new frontier in hydropower technology. This study presents an economical method for crafting droplet generators using common materials such as solid polytetrafluoroethylene (PTFE) films and readily available tapes, eliminating the need for specialized cleanroom facilities. A thorough investigation into voltage-limiting factors, encompassing device capacitance and induced electrode charges, reveals specific areas with potential for optimization. A substantial enhancement in the open-circuit voltage (Voc) was achieved, reaching approximately 282.2 ± 27.9 V-an impressive increase of around 60 V compared to earlier benchmarks. One device showcased its capability to power 100 LEDs concurrently, underscoring its efficacy. Ten such devices created diverse luminous patterns with uniform light intensity for each LED, showcasing the practical potential of the approach. The methodology's cost-effectiveness results in a remarkable cost reduction compared to solution-based materials, paving the way for the widespread adoption of large-scale water droplet energy harvesting.

Radiative cooling for vertical solar panels.

Radiative cooling presents a method for reducing the operational temperature of solar panels without additional energy consumption. However, its applicability to PV modules has been limited by the thermal properties of existing materials. To overcome these challenges, we introduce a V-shaped design that enhances cooling in vertical PV modules by effectively harnessing thermal radiation from both the front and rear sides, resulting in a substantial temperature reduction of 10.6°C under 1 sun illumination in controlled laboratory conditions. Field tests conducted in warm and humid conditions, specifically in Thuwal, Saudi Arabia, demonstrate a remarkable 15% increase in efficiency while maintaining an operating temperature 0.2°C lower than that of conventional horizontal PV modules, corresponding to a significant 16.8% increase in power output. Our innovative V-shaped design offers a promising thermal strategy suitable for diverse climates, contributing to improved performance and reduced module temperatures, thereby supporting the global pursuit of carbon neutrality.

Atmospheric-moisture-induced polyacrylate hydrogels for hybrid passive cooling.

Heat stress is being exacerbated by global warming, jeopardizing human and social sustainability. As a result, reliable and energy-efficient cooling methods are highly sought-after. Here, we report a polyacrylate film fabricated by self-moisture-absorbing hygroscopic hydrogel for efficient hybrid passive cooling. Using one of the lowest-cost industrial materials (e.g., sodium polyacrylate), we demonstrate radiative cooling by reducing solar heating with high solar reflectance (0.93) while maximizing thermal emission with high mid-infrared emittance (0.99). Importantly, the manufacturing process utilizes only atmospheric moisture and requires no additional chemicals or energy consumption, making it a completely green process. Under sunlight illumination of 800 W m-2, the surface temperature of the film was reduced by 5 °C under a partly cloudy sky observed at Buffalo, NY. Combined with its hygroscopic feature, this film can simultaneously introduce evaporative cooling that is independent of access to the clear sky. The hybrid passive cooling approach is projected to decrease global carbon emissions by 118.4 billion kg/year compared to current air-conditioning facilities powered by electricity. Given its low-cost raw materials and excellent molding feature, the film can be manufactured through simple and cost-effective roll-to-roll processes, making it suitable for future building construction and personal thermal management needs.

Simultaneous Detection of Tumor Derived Exosomal Protein-MicroRNA Pairs with an Exo-PROS Biosensor for Cancer Diagnosis.

Tumor derived exosomes (TEXs) have emerged as promising biomarkers for cancer liquid biopsy. Conventional methods (such as ELISA and qRT-PCR) and emerging biosensing technologies mainly detect a single type of exosomal biomarker due to the distinct properties of different biomolecules. Sensitive detection of two different types of TEX biomarkers, i.e., protein and microRNA combined biomarkers, may greatly improve cancer diagnostic accuracy. We developed an exosome protein microRNA one-stop (Exo-PROS) biosensor that not only selectively captured TEXs but also enabled in situ, simultaneous detection of TEX protein-microRNA pairs via a surface plasmon resonance mechanism. Exo-PROS assay is a fast, reliable, low sample consumption, and user-friendly test. With a total of 175 cancer patients and normal controls, we demonstrated that TEX protein-microRNA pairs measured by Exo-PROS assay detected lung cancer and breast cancer with 99% and 96% accuracy, respectively. Exo-PROS assay also showed superior diagnostic performance to conventional ELISA and qRT-PCR methods. Our results demonstrated that Exo-PROS assay is a potent liquid biopsy assay for cancer diagnosis.

Imaging-based intelligent spectrometer on a plasmonic rainbow chip.

Compact, lightweight, and on-chip spectrometers are required to develop portable and handheld sensing and analysis applications. However, the performance of these miniaturized systems is usually much lower than their benchtop laboratory counterparts due to oversimplified optical architectures. Here, we develop a compact plasmonic "rainbow" chip for rapid, accurate dual-functional spectroscopic sensing that can surpass conventional portable spectrometers under selected conditions. The nanostructure consists of one-dimensional or two-dimensional graded metallic gratings. By using a single image obtained by an ordinary camera, this compact system can accurately and precisely determine the spectroscopic and polarimetric information of the illumination spectrum. Assisted by suitably trained deep learning algorithms, we demonstrate the characterization of optical rotatory dispersion of glucose solutions at two-peak and three-peak narrowband illumination across the visible spectrum using just a single image. This system holds the potential for integration with smartphones and lab-on-a-chip systems to develop applications for in situ analysis.

Nanostructured Gallium Nitride Membrane at Wafer Scale for Photo(Electro)catalytic Polluted Water Remediation.

Photo(electro)catalysis methods have drawn significant attention for efficient, energy-saving, and environmental-friendly organic contaminant degradation in wastewater. However, conventional oxide-based powder photocatalysts are limited to UV-light absorption and are unfavorable in the subsequent postseparation process. In this paper, a large-area crystalline-semiconductor nitride membrane with a distinct nanoporous surface is fabricated, which can be scaled up to a full wafer and easily retrieved after photodegradation. The unique nanoporous surface enhances broadband light absorption, provides abundant reactive sites, and promotes the dye-molecule reaction with adsorbed hydroxyl radicals on the surface. The superior electric contact between the nickel bottom layer and nitride membrane facilitates swift charge carrier transportation. In laboratory tests, the nanostructure membrane can degrade 93% of the dye in 6 h under illumination with a small applied bias (0.5 V vs Ag/AgCl). Furthermore, a 2 inch diameter wafer-scale membrane is deployed in a rooftop test under natural sunlight. The membrane operates stably for seven cycles (over 50 h) with an outstanding dye degradation efficiency (>92%) and satisfied average total organic carbon removal rate (≈50%) in each cycle. This demonstration thus opens the pathway toward the production of nanostructured semiconductor layers for large-scale and practical wastewater treatment using natural sunlight.

Three-dimensional open architecture enabling salt-rejection solar evaporators with boosted water production efficiency.

Direct solar desalination exhibits considerable potential for alleviating the global freshwater crisis. However, the prevention of salt accumulation while maintaining high water production remains an important challenge that limits its practical applications because the methods currently employed for achieving rapid salt backflow usually result in considerable heat loss. Herein, we fabricate a solar evaporator featuring vertically aligned mass transfer bridges for water transport and salt backflow. The 3D open architecture constructed using mass transfer bridges enables the evaporator to efficiently utilize the conductive heat that would otherwise be lost, significantly improving the water evaporation efficiency without compromising on salt rejection. The fabricated evaporator can treat salt water with more than 10% salinity. Moreover, it can continuously and steadily work in a real environment under natural sunlight with a practical solar-to-water collection efficiency of >40%. Using the discharged water from reverse osmosis plants and sea water from the Red Sea, the evaporator demonstrates a daily freshwater generation rate of ~5 L/m2, which is sufficient to satisfy individual drinking water requirements. With strong salt rejection, high energy efficiency, and simple scalability, the 3D evaporator has considerable promise for freshwater supply for water-stressed and off-grid communities.

Superhydrophobic 3D-Assembled Metallic Nanoparticles for Trace Chemical Enrichment in SERS Sensing.

The performance of surface-enhanced Raman spectroscopy (SERS) is determined by the interaction between highly diluted analytes and boosted localized electromagnetic fields in nanovolumes. Although superhydrophobic surfaces are developed for analyte enrichment, i.e., to concentrate and transfer analytes toward a specific position, it is still challenging to realize reproducible, uniform, and sensitive superhydrophobic SERS substrates over large scales, representing a major barrier for practical sensing applications. To overcome this challenge, a superhydrophobic SERS chip that combines 3D-assembled gold nanoparticles on nanoporous substrates is proposed, for a strong localized field, with superhydrophobic surface treatment for analyte enrichment. Intriguingly, by concentrating droplets in the volume of 40 µL, the sensitivity of 1 nm is demonstrated using 1,2-bis(4-pyridyl)-ethylene molecules. In addition, this unique chip demonstrates a relative standard deviation (RSD) of 2.2% in chip-to-chip reproducibility for detection of fentanyl at 1 µg mL-1 concentration, revealing its potential for quantitative sensing of chemicals and drugs. Furthermore, the trace analysis of fentanyl and fentanyl-heroin mixture in human saliva is realized after a simple pretreatment process. This superhydrophobic chip paves the way toward on-site and real-time drug sensing to tackle many societal issues like drug abuse and the opioid crisis.

Correlate light-matter interactions in different spectral regimes.

Using mid-infrared plasmons to trigger visible surface enhanced Raman spectroscopy signals within a nanocavity represents new opportunities for fundamental investigation of light-matter interaction within quantum regimes, requiring improved sensing capabilities enabled by well-designed nano/microstructures and characterization systems.

A Compact Surface Plasmon Resonance Biosensor for Sensitive Detection of Exosomal Proteins for Cancer Diagnosis.

Exosomes are nanosized (50-150 nm) extracellular vesicles released by all types of cells in the body. They transport various biological molecules, such as DNAs, RNAs, proteins, and lipids from parent cells to recipient cells for intercellular communication. Exosomes, especially those from tumor cells, are actively involved in caner development, metastasis, and drug resistance. Recently, many studies have shown that exosomal proteins are promising biomarkers for cancer screening, early detection and prognosis. Among many detection techniques, surface plasmon resonance (SPR) is a highly sensitive, label-free, and real-time optical detection method. Commercial prism-based wavelength/angular-modulated SPR sensors afford high sensitivity and resolution, but their large footprint and high cost limit their adaptability for clinical settings. We have developed an intensity-modulated, compact SPR biosensor (25 cm × 10 cm × 25 cm) for the detection of exosomal proteins. We have demonstrated the potential application of the compact SPR biosensor in lung cancer diagnosis using exosomal epidermal growth factor receptor (EGFR) and programmed death-ligand 1 (PD-L1) as biomarkers. The compact SPR biosensor offers sensitive, simple, fast, user-friendly, and cost-effective detection of exosomal proteins, which may serve as an in vitro diagnostic test for cancer.

Super-Resolution Displacement Spectroscopic Sensing over a Surface "Rainbow".

Subwavelength manipulation of light waves with high precision can enable new and exciting applications in spectroscopy, sensing, and medical imaging. For these applications, miniaturized spectrometers are desirable to enable the on-chip analysis of spectral information. In particular, for imaging-based spectroscopic sensing mechanisms, the key challenge is to determine the spatial-shift information accurately (i.e., the spatial displacement introduced by wavelength shift or biological or chemical surface binding), which is similar to the challenge presented by super-resolution imaging. Here, we report a unique "rainbow" trapping metasurface for on-chip spectrometers and sensors. Combined with super-resolution image processing, the low-setting 4× optical microscope system resolves a displacement of the resonant position within 35 nm on the plasmonic rainbow trapping metasurface with a tiny area as small as 0.002 mm2. This unique feature of the spatial manipulation of efficiently coupled rainbow plasmonic resonances reveals a new platform for miniaturized on-chip spectroscopic analysis with a spectral resolution of 0.032 nm in wavelength shift. Using this low-setting 4× microscope imaging system, we demonstrate a biosensing resolution of 1.92 × 109 exosomes per milliliter for A549-derived exosomes and distinguish between patient samples and healthy controls using exosomal epidermal growth factor receptor (EGFR) expression values, thereby demonstrating a new on-chip sensing system for personalized accurate bio/chemical sensing applications.

Sustainable and Inexpensive Polydimethylsiloxane Sponges for Daytime Radiative Cooling.

Radiative cooling is an emerging cooling technology that can passively release heat to the environment. To obtain a subambient cooling effect during the daytime, chemically engineered structural materials are widely explored to simultaneously reject sunlight and preserve strong thermal emission. However, many previously reported fabrication processes involve hazardous chemicals, which can hinder a material's ability to be mass produced. In order to eliminate the hazardous chemicals used in the fabrication of previous works, this article reports a white polydimethylsiloxane (PDMS) sponge fabricated by a sustainable process using microsugar templates. By substituting the chemicals for sugar, the manufacturing procedure produces zero toxic waste and can also be endlessly recycled via methods widely used in the sugar industry. The obtained porous PDMS exhibits strong visible scattering and thermal emission, resulting in an efficient temperature reduction of 4.6 °C and cooling power of 43 W m-2 under direct solar irradiation. In addition, due to the air-filled voids within the PDMS sponge, its thermal conductivity remains low at 0.06 W (m K)-1 . This unique combination of radiative cooling and thermal insulation properties can efficiently suppress the heat exchange with the solar-heated rooftop or the environment, representing a promising future for new energy-efficient building envelope material.

Vapor condensation with daytime radiative cooling.

A radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor. This effect has been known for centuries, and is exploited by some insects to survive in dry deserts. Humans have also been using radiative condensation for dew collection. However, all existing radiative vapor condensers must operate during the nighttime. Here, we develop daytime radiative condensers that continue to operate 24 h a day. These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy. Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies.

Decomposition of dimethyl methylphosphonate vapor on ultrathin-film titania photocatalytic light absorber.

The decomposition of chemical warfare agent simulant, dimethyl methylphophonate (DMMP) vapor, was investigated on an ultrathin film titania (TiO2) photocatalytic light absorber. The light absorber contains an aluminum (Al) reflector and the TiO2 thin film with different thicknesses, sequentially deposited on a supportive glass substrate. The designed structure constructs a nanocavity that exhibits strong light absorption within the photocatalytic TiO2 ultrathin film. Thus, the intrinsic trade-off between optical absorption and charge carrier extraction efficiency, i.e., a light absorber should be thick enough to absorb the light allowable by its band gap but thin enough to allow charge carrier extraction for catalytic reactions, is conquered. The TiO2/Al light absorber significantly boosted TiO2 photocatalytic activity compared to the benchmark Aeroxide®P25 catalyst (i.e., up to 2013 times increase in reaction rate). The effects of reactant (i.e. DMMP, water and oxygen, respectively) partial pressure and reaction temperature on photocatalytic decomposition of DMMP by the ultrathin-film TiO2 photocatalytic light absorber were studied. Kinetic data of the DMMP decomposition can be described by the Langmuir-Hinshelwood model.

Iridescence-controlled and flexibly tunable retroreflective structural color film for smart displays.

Structural color materials, which use nano- or microstructures to reflect specific wavelengths of ambient white light, have drawn much attention owing to their wide applications ranging from optoelectronics, coatings, to energy-efficient reflective displays. Although various structural color materials based on specular or diffuse reflection have been demonstrated, neither efficient retroreflective structural colors nor iridescent and non-iridescent colors to different observers simultaneously were reported by existing artificial or natural structural color materials. Here, we show that by partially embedding a monolayer of polymer microspheres on the sticky side of a transparent tape, the spontaneously formed interferometric structure on the surface of air-cushioned microspheres can lead to unique structural colors that remain non-iridescent under coaxial illumination and viewing conditions, but appear iridescent under noncoaxial illumination and viewing conditions. Our findings demonstrate a smart, energy-efficient, and tunable retroreflective structural color material that is especially suitable for nighttime traffic safety and advertisement display applications.

Generation of a Nondiffracting Superchiral Optical Needle for Circular Dichroism Imaging of Sparse Subdiffraction Objects.

Chirality describes not only the structural property of three-dimensional objects, but also an intrinsic feature of electromagnetic fields. Here we report a strategy to realize a Bessel beam superchiral "needle" by focusing a twisted radially polarized beam on a planar dielectric interface. By tailoring the light spatial distribution in the pupil plane of a high numerical aperture lens, the chirality of the local field at the focus can be enhanced by 11.9-fold than that of a circular polarized beam. Through a combined interaction of chiral and achiral transitions, the dimension of the region with enhanced chiral sensitivity can be shrunk down to λ/25. This theoretical work paves the way towards a completely new label-free imaging technique using the enhanced circular dichroism for sparse subdiffraction chiral objects (e.g., individual molecules).

Plasmonic Interferometer Array Biochip as a New Mobile Medical Device for Cancer Detection.

We report a plasmonic interferometer array (PIA) sensor and demonstrate its ability to detect circulating exosomal proteins in real-time with high sensitivity and low cost to enable the early detection of cancer. Specifically, a surface plasmon wave launched by the nano-groove rings interferes with the free-space light at the output of central nano-aperture and results in an intensity interference pattern. Under the single-wavelength illumination, when the target exosomal proteins are captured by antibodies bound on the surface, the biomediated change in the refractive index between the central aperture and groove rings causes the intensity change in transmitted light. By recording the intensity changes in real-time, one can effectively screen biomolecular binding events and analyze the binding kinetics. By integrating signals from multiple sensor pairs to enhance the signal-to-noise ratio, superior sensing resolutions of 1.63×10-6 refractive index unit (RIU) in refractive index change and 3.86×108 exosomes/mL in exosome detection were realized, respectively. Importantly, this PIA sensor can be imaged by a miniaturized microscope system coupled with a smart phone to realize a portable and highly sensitive healthcare device. The sensing resolution of 9.72×109 exosomes/mL in exosome detection was realized using the portable sensing system building upon a commercial smartphone.