Passive daytime radiative cooling (PDRC) has drawn significant attention recently for electricity-free cooling. Porous polymers are attractive for PDRC since they have excellent performance and ...scalability. A fundamental question remaining is how PDRC performance depends on pore properties (e.g., radius, porosity), which is critical to guiding future structure designs. In this work, optical simulations are carried out to answer this question, and effects of pore size, porosity, and thickness are studied. We find that mixed nanopores (e.g., radii of 100 and 200 nm) have a much higher solar reflectance R̅ solar (0.951) than the single-sized pores (0.811) at a thickness of 300 μm. With an Al substrate underneath, R̅ solar, thermal emittance ε̅LWIR, and net cooling power P cool reach 0.980, 0.984, and 72 W/m2, respectively, under a semihumid atmospheric condition. These simulation results provide a guide for designing high-performance porous coating for PDRC applications.
Radiative cooling is a promising passive cooling technology that reflects sunlight and emits heat to deep space without any energy consumption. Current research mainly focuses on cooling ...non‐heat‐generating objects (e.g., water) to a deep subambient temperature under sunlight. Toward real‐world applications, however, cooling outdoor objects that generate tremendous heat and have a temperature higher than ambient (e.g., communication base stations and data centres) remains a challenge. Herein, a scalable photonic film is prepared by introducing 2D dielectric nanoplates with high backward scattering efficiency into a polymer using a simulation aided thermo‐optical design. It is demonstrated that the dielectric nanoplates can break the trade‐off between optical reflection and thermal dissipation of conventional radiative coolers. The photonic film exhibits superior solar reflectance (98%) and has a stronger heat dissipation ability compared to the matrix. It exhibits ≈4 °C subambient cooling performance under direct sunlight and ≈9 °C cooling performance at night. Moreover, it also demonstrates remarkable above‐ambient cooling performance by reducing the underlying heater temperature of ≈18 °C in comparison with traditional polymers under sunlight. The dielectric nanoplates reported here provide an innovative strategy for applications related to light management beyond subambient and above‐ambient radiative cooling.
A thermo‐optically designed photonic film, which accounts for both subambient and above‐ambient radiative cooling is prepared. It consists of a visibly transparent polymer encapsulating 2D dielectric nanoplates. The nanoplates substantially improve all the advantageous properties of the photonic film that endow it with a record high solar reflectance (98%), a strong thermal emittance (90%), and an unprecedented heat dissipation ability.
Recent achievements in the field of tactile sensing has enhanced the dexterity of robots interacting with their environments. Superior to other transduction mechanisms, vision-based tactile sensing ...enables high-resolution sensing of the contact surface. Accordingly, many vision-based tactile sensors have been introduced in recent years, all of which are designed and fabricated based on a trial-and-error approach with limited prior system modeling and simulation. In this study, we introduce a detailed framework for the development of a vision-based tactile sensor with markers motion mechanism. We start with the design and coupled simulation of the mechanical and optical subsystems followed by fabrication, testing, and validation of the proposed sensor. An uncertainty analysis is carried out during the design stage where various errors are propagated to determine the expected sensor accuracy. The simulated sensor showed a maximum error of 0.15 newtons with the error for the camera distance to the rigid membrane having the highest contribution. After fabrication of the sensor, it is observed that there is a very good agreement between simulation and experimental results. The sensor was tested for sensing tangential forces (up to slip) along two directions and normal force (up to 5 newtons) at 30 Hz rate with measurement errors (95 % confidence interval) of 0.39 newton, 0.11 newton, and 0.12 newton, respectively. The sensor detected the slip in 97 % of the tests with an average latency of 10 frames.
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•Multiphysics simulation framework to assess a vision-based tactile sensor.•Uncertainty analysis in simulation stage to obtain underlying errors.•Sensor design and fabrication and comparing experimental and simulation results.•Force estimation using machine-learning methods and comparing the results.•Slip detection using estimated force variance with 97 % accuracy in 10 frames.
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•Optical simulations, validated by experiments, reveal that a gradient distribution of nanopores with a random pattern significantly enhances solar reflectance by 153.4% under direct ...sunlight.•The spatial arrangement of nanopores is crucial for maximizing the passive daytime radiative cooling performance.•Strategic nanopore distribution in polymer films increases daytime radiative cooling power by 39.4 W/m2, demonstrating a substantial improvement over random pore arrangements.
Owing to of its freedom from energy inputs, radiative cooling is emerging as a frontier in renewable energy research. Recent advances in nanophotonic structures have enabled scalable passive daytime radiative cooling (PDRC), such as porous polymer films, which can spontaneously reflect solar irradiance and emit heat to the ultra-cold outer space. However, there is still limited fundamental understanding of these nanophotonic structures underlying the cooling effects of these porous polymer-based PDRC films. Hence, we performed optical simulations validated by experiments to quantify how the spatial distribution of nanopores in the polymer film affect its PDRC performance. Our simulation results showed that the influence of spatial distribution of pores on the PDRC performance replies significantly on solar reflectance. A gradient distribution of pores with random pattern can remarkably enhance solar reflectance under direct sunlight up to 153.4 %, while maintaining a slight variation of thermal emittance <4.4 %. With such optimized spatial distribution of pores in polymer, daytime radiative cooling power increased 39.4 W/m2 under direct sunlight in comparison with the randomly distributed pores. These findings indicate that the spatial distribution of nanopores is critical both for demonstrating the cooling effect and for the rational design of nanophotonic structures in high-performance PDRC applications.
A universal strategy for efficient light trapping through the incorporation of gold nanorods on the electron transport layer (rear) of organic photovoltaic devices is demonstrated. Utilizing the ...photons that are transmitted through the active layer of a bulk heterojunction photovoltaic device and would otherwise be lost, a significant enhancement in power conversion efficiency (PCE) of polyN‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole):phenyl‐C71‐butyric acid methyl ester (PCDTBT:PC71BM) and poly4,8‐bis(2‐ethylhexyl)oxybenzo1,2‐b:4,5‐b′dithiophene‐2,6‐diyl3‐fluoro‐2‐(2‐ethylhexyl)carbonylthieno3,4‐b thiophenediyl (PTB7):PC71BM by ≈13% and ≈8%, respectively. PCEs over 8% are reported for devices based on the PTB7:PC71BM blend. A comprehensive optical and electrical characterization of our devices to clarify the influence of gold nanorods on exciton generation, dissociation, charge recombination, and transport inside the thin film devices is performed. By correlating the experimental data with detailed numerical simulations, the near‐field and far‐field scattering effects are separated of gold nanorods (Au NRs), and confidently attribute part of the performance enhancement to the enhanced absorption caused by backscattering. While, a secondary contribution from the Au NRs that partially protrude inside the active layer and exhibit strong near‐fields due to localized surface plasmon resonance effects is also observed but is minor in magnitude. Furthermore, another important contribution to the enhanced performance is electrical in nature and comes from the increased charge collection probability.
High efficiency organic photovoltaic (OPV) devices are fabricated based a novel and universal light trapping mechanism, using gold nanorods (Au NRs) as back contact reflectors. The incorporation of Au NRs inside the back contact interfacial layer (titanium sub oxide) gives rise to a device efficiency of ≈13%, compared to the record performance of 8.25%. This is revealed to be mainly due to scattering by a combination of theoretical and experimental results.
Microneedles (MNs) are an emerging technology in pharmaceutics and biomedicine, and are ready to be commercialized in the world market. However, solid microneedles only allow small doses and ...time-limited administration rates. Moreover, some well-known and already approved drugs need to be re-formulated when supplied by MNs. Instead, hollow microneedles (HMNs) allow for rapid, painless self-administrable microinjection of drugs in their standard formulation. Furthermore, body fluids can be easily extracted for analysis by a reverse use of HMNs, thus making them perfect for sensing issues and theranostics applications. The fabrication of HMNs usually requires several many-step processes, increasing the costs and consequently decreasing the commercial interest. Photolithography is a well-known fabrication technique in microelectronics and microfluidics that fabricates MNs. In this paper, authors show a proof of concept of a patented, easy and one-shot fabrication of two kinds of HMNs: (1) Symmetric HMNs with a "volcano" shape, made by using a photolithographic mask with an array of transparent symmetric rings; and (2) asymmetric HMNs with an oblique aperture, like standard hypodermic steel needles, made by using an array of transparent asymmetric rings, defined by two circles, which centers are slightly mismatched. Simulation of light propagation, fabrication process, and preliminary results on ink microinjection are presented.
This work presents an experimental study to emulate solutions of Lippmann-Schwinger equations for scattering by an elliptical billiard. The probability density patterns are recovered in the intensity ...of a laser beam scattered by a Spatial Light Modulator (SLM). This result opens an interesting perspective to explore scattering solutions, mainly when physical distributions with specific properties are required. Optical simulations performed by experiments with intense laser beams have been applied for many quantum systems and in this work, we expand this application.
•Optical simulation of solution of the Lippmann-Schwinger equation.•Different elliptical billiard is explored for hologram construction.•Probability density distribution for scattering is emulated by a laser beam.•Remarkable agreement between optical and theoretical results.
In this letter, we apply an optical setup to simulate the coherent evolution of an atomic wavepacket under the action of a standing-wave optical pulse sequence. Predicted population oscillations in ...J. Opt. Soc. Am. B 39, 3012 (2022) have been observed, and the beam divergence angle, which corresponds to the atomic momentum width, has been obtained by fitting the data. Consequently, we confirm the viability of employing standing-wave optical pulse sequences for measuring the ultra-narrow momentum distribution of atoms. In addition, we introduce a fitting method suitable for data obtained under non-ideal experimental conditions, which serves as a reference for similar experiments in atomic ultra-low temperature measurements.
•We confirm the viability of employing atom interferometry to measure the temperature of ultracold atoms.•We develop a fitting method for the data obtained under non-ideal conditions.•It provides a sensitive method for measuring the divergence angle of Gaussian beams.
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