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Lithography is one of the most key technologies for integrated circuit (IC) manufacturing and micro/nano-functional device fabrication, while the imaging objective lens plays one important role. Due to the curved surface of the conventional objective lens, the imaging field of view is limited and the objective lens system is complex. In this paper, a planar objective lens based on the optical negative refraction principle is demonstrated for achieving optical axis free and long depth of focus imaging nanolithography. Through employing a hyperbolic metamaterial composed of silver/titanium dioxide multilayers, plasmonic waveguide modes could be generated in multilayers, which results in optical negative refraction and then flat imaging at ultraviolet wavelength. The corresponding imaging characteristics are investigated in simulation and experiment. At the I-line wavelength of 365 nm, the highest imaging resolution of 165 nm could be realized in the 100 nm photoresist layer under the working gap of 100 nm between the objective lens and substrate. Moreover, this planar objective lens has good ability for cross-scale and two-dimensional imaging lithography, and is similar to a conventional projection objective lens. It is believed that this kind of planar objective lens will provide a promising avenue for low-cost nanofabrication scenarios in the near future.

Robust and efficient manipulation of electron spin qubits in quantum dots is of great significance for the reliable realization of quantum computers and execution of quantum algorithms. In this paper, we study the robust control on a singlet-triplet qubit based on inverse engineering, one technique of shortcuts to adiabaticity (STA), in a nanowire double quantum dot in the presence of magnetic field and strong spin-orbit coupling. The optimization of STA with respect to the systematic errors, contributed from the control field and the perturbative interaction, is explored. Moreover, we also apply optimal control techniques combining with STA, referred to as robust inverse optimization, to design optimal control fields and optimal operation time. This article is part of the theme issue ‘Shortcuts to adiabaticity: theoretical, experimental and interdisciplinary perspectives’.

High-sensitivity, reproducible, and low-cost substrate has been a major obstacle for practical sensing application of surface-enhancement Raman scattering (SERS). In this work, we report a type of simple SERS substrate which is composed of metal-insulator-metal (MIM) structure of Ag nanoisland (AgNI)-SiO2-Ag film (AgF). The substrates are fabricated by only evaporation and sputtering processes, which are simple, fast and low-cost. By combining the hotspots and interference-enhanced effects in AgNIs and the plasmonic cavity (SiO2) between AgNIs and AgF, the proposed SERS substrate shows an enhancement factor (EF) of 1.83 × 108 with limit of detection (LOD) down to 10−17 mol/L for rhodamine 6 G (R6G) molecules. The EFs are ∼18 times higher than that of conventional AgNIs without MIM structure. In addition, the MIM structure shows excellent reproducibility with relative standard deviation (RSD) less than 9%. The proposed SERS substrate is fabricated only with evaporation and sputtering technique and the conventionally used lithographic methods or chemical synthesis are not required. This work provides a simple way to fabricate ultrasensitive and reproducible SERS substrates which show great promise for developing various biochemical sensors with SERS.

Neonatal jaundice is a common health problem seen in 60–80% of newborns. Electronic search in nine databases was done for randomized controlled trials. Twenty seven studies were eligible for quantitative analysis. For neonates requiring phototherapy (PT), in 3rd and 4th days of life, massage and phototherapy was more effective in reducing bilirubin, compared to phototherapy alone. However, this effect became insignificant in the 14th day of life. In contrast, massage with enema and phototherapy significantly reduced bilirubin at the age of 14 days. For neonates not requiring PT, the best reduction was observed with the acupressure massage between the 3rd and 7th days. In the 14th day, massage combined with bathing appears to be the most effective. Massage therapy could be an effective adjuvant to PT in order to reduce the PT duration. However, it did not reduce the requirement for PT.

Organic blue fluorescent emitters’ emissions are highly desirable for high-resolution organic light-emitting diode (OLED) display technology. In this work, a design strategy to realize narrowband emission of organic blue fluorescent emitters by connecting carbazole and amine, named ABFCz and ABFAn, respectively, with anthracene[2,3-b]benzofuran as rigid groups is reported for the first time. The developed materials can achieve high efficiency and long life. Studies of the doped devices show that ABFCz-based blue-emitting OLEDs achieve a maximum current efficiency of 6.96 cd A−1 with a narrow full width at half maximum (FWHM) of 44 nm, as well as a Commission Internationale de l’Eclairage (CIE) coordinate of (0.15, 0.14). A maximum external quantum efficiency (EQEmax) of 7.7% is also achieved. Meanwhile, the ABFAn emitter-based devices exhibit blue emission with a maximum current efficiency of up to 9.20 cd A−1 (EQEmax of 11.4%) with a FWHM of 44 nm, as well as a CIE coordinate of (0.14, 0.13). The devices are based on an ABFAn operating lifetime test LT90 (luminance decays to 90% of the initial brightness) of 202 h at an initial luminance of 1000 cd m−2. The results show that anthracene[2,3-b]benzofuran can be modified with a higher glass transition temperature (T g) to achieve high-efficiency and stable-operating-lifetime blue light devices. Our work may provide a new approach for designing high-efficiency blue materials.

Background: Granular cell tumors (GCTs) are rare tumors probably originating from neurogenic Schwann cells. The aim was to evaluate the safety and feasibility of endoscopic resection for esophageal GCTs. Methods: The study retrospectively analyzed patients with pathologically diagnosed esophageal GCTs in our center from February 2012 to December 2020. Clinicopathological characteristics, endoscopic features and clinical outcomes were collected and analyzed. Results: 12 males and 10 females were identified. Lesions were located in the upper, middle and lower esophagus in three, six and thirteen cases respectively. 14 lesions (63.6%) exhibited white-to-yellow discoloration. The mean maximum diameter of these lesions was 5.7±2.2 mm (range 2-11.6 mm). The most lesions (91%) were located in the mucosa or submucosa layer, and 2 lesions (9.0%) were in the muscularis propria layer. Endoscopic mucosal resection (n=17), endoscopic submucosal dissection (n=4) and endoscopic submucosal excavation (n=1) were performed. En bloc resection was achieved in 20 lesions (90.9%). The R0 resection was achieved in 20 lesions (90.9%). No patients experienced intraoperative perforation or delayed bleeding in the mean length of postoperative hospital stay of 4.2±2.1 days (range 1-9 days). All patients had no recurrence or metastasis during the mean follow-up period of 48.1±27.2 months (range 2-102 months). Conclusion: Endoscopic resection is safe and effective for management of esophageal GCTs. Clinically, the appropriate approach of endoscopic resection should be selected according to the origin and size of the lesion.

Geometric metasurfaces have shown superior phase control capacity owing to the geometric nature of their phase profile. The existing geometric metasurfaces are generally composed of metal-dielectric composites or all-dielectric subwavelength structures. Here, a novel configuration, all-metallic structure, is proposed to achieve broadband and high-performance electromagnetic wavefront manipulation based on the geometric phase. A catenary model is built to describe the optical dispersion and guide the design of metasurfaces. Two metadevices including a beam deflector and a hologram are designed and experimentally demonstrated in the infrared regime, with the measured optical efficiency up to 84% (the simulated efficiency reaches 93%). Compared to previous metal-insulator-metal structures, this approach can realize higher efficiency and broader operating bandwidth owing to its lower ohmic loss. This design strategy is universal and can be easily scaled to any other spectra without complex optimization. Moreover, since metals have excellent mechanical and physical properties, such as good thermal and electrical conductivity, this all-metallic structure may provide a new thinking on interdisciplinary research.

Optical vortices (OVs) created from helical modes of light have extensive applications in optical manipulation, imaging, and optical communications. Moreover, modulated optical vortices (MOVs) with modified wavefronts could provide new opportunities for fractionating particles and actuating microelectromechanical systems. Traditional devices for generating MOVs include spatial light modulators, spiral phase plates, and so on. However, such bulky devices are difficult to be applied to high-level integrated optical systems. Besides, other MOV generators are typically static and polarization-insensitive. Here, we proposed an all-dielectric metasurface to generate polarization-sensitive MOVs. The intensity patterns of the OVs can be modulated by adding a tangential modulation factor in the phase profile. Independent manipulation of two orthogonal polarizations was adopted via tailoring the geometric parameters of silicon (Si) pillars. We experimentally demonstrated that the metasurface could generate a doughn...

Nanofocusing beyond the diffraction limit has received a significant amount of attention in recent years due to its versatility. In this paper, subdiffraction nanofocusing of circularly polarized light is achieved in a plasmonic cavity lens by constructive interference of plasmonic waveguide modes launched by a spiral slot. By employing a plasmonic cavity lens composed of a metal–insulator–metal (MIM) waveguide, the plasmonic mode wavelength could be suppressed efficiently and thus a deep subwavelength focal spot could be attained. Simulated and lithography experimental results indicate that a focal spot with 60 nm size and 30 nm depth of focus could be produced in a photoresist under laser illumination with 375 nm wavelength. Moreover, the plasmonic cavity lens could tolerate a maximum air gap between the mask and the lens of 40 nm, which facilitates practical applications. Additionally, defocusing would happen for a spiral slot with opposite chirality. This design provides a simple solution for deep subwavelength light confinement and may find applications in nanolithography, super resolution imaging, high density data storage, etc.

The polarization singularity in momentum space has recently been discovered as a new class of topological signatures of Bloch modes in photonic crystal slabs concerning the far-field radiations, beyond its near-field description with widely explored topological band theory. Bound states in the continuum (BICs) in photonic crystal slabs are demonstrated as vortex eigenpolarization singularities in momentum space and the circular polarization points ($C$ points) are also obtained based on BICs, opening up more possibilities for exotic light scattering and various topological phenomena of singular optics. Here, focusing on the nondegenerate bands, we report the generation to annihilation of two pairs of $C$ points in momentum space in the photonic crystal slabs with inversion symmetry but broken up-down mirror symmetry. Interestingly, as the $C$ points evolve with the structure parameter, we find two merging processes of $C$ points, where an accidental at-$\mathrm{\ensuremath{\Gamma}}$ BIC and unidirectional radiative resonances with leaky channels of drastically different radiative lifetime emerge. The whole evolution is governed by the global charge conservation and the sum of topological charges equals to zero. Our findings suggest a novel recipe for dynamic generation and manipulation of various polarization singularities in momentum space and might shed new light to control the resonant and topological properties of light-matter interactions.

Bound states in the continuum (BICs) are localized states despite in a radiation continuum, rendering the ultra-high quality factor for enhanced light–matter interactions and supporting exotic topological properties. So far, most of studied BICs in photonic crystal (PhC) slabs are only vertically localized, i.e. allowing propagations in the plane of slab therein but forbidding radiations, and the density of optical states (DOS) at their frequencies is limited due to the steep dispersion characteristics. Here, we report a BIC existing on a flatband of symmetry-broken PhC slab. The flatband, associated with largely reduced group velocity, significantly sharpens the DOS at the frequency of BIC, which can be realized via finely controlling broken vertical symmetry in the PhC slab. The effect of broken symmetry is revealed in a simple effective Hamiltonian near the second-order Γ point of such system. Our results show the simultaneous engineering of dispersion and leaky characteristics of modes, offering new opportunities to boost light–matter interactions and to enhance the performance of photonic devices.

Naturally-occurring thermal materials usually possess specific thermal conductivity (κ), forming a digital set of κ values. Emerging thermal metamaterials have been deployed to realize effective thermal conductivities unattainable in natural materials. However, the effective thermal conductivities of such mixing-based thermal metamaterials are still in digital fashion, i.e., the effective conductivity remains discrete and static. Here, we report an analog thermal material whose effective conductivity can be in-situ tuned from near-zero to near-infinity κ. The proof-of-concept scheme consists of a spinning core made of uncured polydimethylsiloxane (PDMS) and fixed bilayer rings made of silicone grease and steel. Thanks to the spinning PDMS and its induced convective effects, we can mold the heat flow robustly with continuously changing and anisotropic κ. Our work enables a single functional thermal material to meet the challenging demands of flexible thermal manipulation. It also provides platforms to investigate heat transfer in systems with moving components., Thermal metamaterials are able to produce unconventional physical properties. Here, the authors demonstrate a thermal metamaterial with conductivity that can be continuously tuned over a very large range.

Advancement in the understanding of biomolecular interactions has benefited from the development of surface imaging microscopy with high sensitivity and contrast. In this work, surface imaging microscopy with tunable penetration depth as short as 20 nm is proposed. By employing a hyperbolic metamaterial (HMM) composed of metal/dielectric multifilms, the deep subwavelength bulk plasmon polaritons (BPPs) are excited as the uniform and large area surface illumination source. Moreover, the penetration depth of the surface illumination structure could be continually tuned by changing the incidence angle of excitation light. In the experiments, a penetration depth of 25–38 nm in air is achieved at 532 nm by the HMM with Ag/SiO2 multilayers. Subsequently, a fluorescence pattern was imaged against another fluorescent background by this surface imaging microscopy, and the results indicate that distinct surface images with high contrast could indeed be obtained under BPP illumination with ultra-short penetration depth. This approach provides a promising avenue for tracking single-molecule and cell plasma membrane events.

Recent strides in microfabrication technologies offer important possibilities for developing microscale robotic systems with enhanced power, functionality and versatility. Previous microrobots fabricated by lithographic techniques usually lack the ability to adaptively deform in confined and constricted spaces and navigate through, therefore hindering their applications in complex biological environments. Here, a microfluidic strategy is combined with a dip-coating process for continuous fabrication of soft helical structures with controllable mechanical property as magnetically propelled microrobots, capable of actively propelling through narrow and sinuous microchannels. Because of their self-adaptive deformation capability, the magnetically propelled soft microrobots can actively navigate through a narrow opening, 2.21 times smaller than the sectional area of the microrobot, and a U-shape-bent capillary, directed by a programmed magnetic field. Additionally, the soft microrobot demonstrates increased swimming speed in a fluid of high viscosity, because of the adaptive tightening deformation of the helix when swimming. This new magnetically propelled soft microrobot and its attractive performance will open up new possibilities for biomedical operation at the micro and nanoscale.

Structural colors emerge when a particular wavelength range is filtered out from a broadband light source. It is regarded as a valuable platform for color display and digital imaging due to the benefits of environmental friendliness, higher visibility, and durability. However, current devices capable of generating colors are all based on direct transmission or reflection. Material loss, thick configuration, and the lack of tunability hinder their transition to practical applications. In this paper, a novel mechanism that generates high-purity colors by photon spin restoration on ultrashallow plasmonic grating is proposed. We fabricated the sample by interference lithography and experimentally observed full color display, tunable color logo imaging, and chromatic sensing. The unique combination of high efficiency, high-purity colors, tunable chromatic display, ultrathin structure, and friendliness for fabrication makes this design an easy way to bridge the gap between theoretical investigations and daily-life applications.

A structured bulk plasmon illumination (BPI) source is designed for achieving a uniform high spatial frequency illumination field. By employing the hyperbolic metamaterial (HMM) composed of alternatively stacked metal and dielectric nanolayers, the deep subwavelength bulk plasmon polaritons (BPPs) can be launched. The obtained BPP modes are then utilized as a structured illumination source for improving the imaging resolution. More importantly, the BPI intensity can be improved remarkably by adding an extra Ag layer to the original BPI source. When two nano-slits are illuminated by the BPI source, the imaging resolution of plasmonic cavity superlens is improved obviously. Especially, after adding an extra Ag layer to the original BPI source, one can find the obvious improvement of the image contrast. The proposed BPI source promises some potential in near-field super resolution lithography.

A miniature evanescent Bessel beam generator is realized by utilizing the combination of metasurfaces based on a concentric grating and hyperbolic metamaterials composed of alternate metal/dielectric multilayers. After introducing the plasmonic cavity lens, the feature size could be compressed to 62 nm (0.17λ0) at the wavelength of 365 nm with a working distance as large as 100 nm. The theoretical models are verified by a set of experiments, providing a promising way to control light at the nanoscale.

Background Neonatal jaundice is a common health problem which is expected to be seen in 60–80% of healthy newborns, with 10% occurrence of hyperbilirubinemia in neonates during first week of life. Massage therapy has been practiced for centuries to gain health benefits in infants. We aimed to evaluate effectiveness of various types of infant massage in reduction of neonatal jaundice and the need for phototherapy (PT). Methods On 26 March 2016, we conducted electronic search term in nine databases, with inclusion of randomized controlled trials (RCTs) that investigated newborn babies receiving massage therapy with documented total bilirubin before and after the treatment. Study protocol was registered on PROSPERO, CRD42016049025. Quality assessment was performed using Cochrane risk of bias tool. Frequentist network meta-analysis (NMA) and meta-analysis (MA) were used to compare all outcomes by each day of follow-up. Results With 363 studies initially identified, 32 were eligible for qualitative analysis and 29 for quantitative analysis. For neonates requiring PT, our NMA results showed that in 3rd day of life, massage and phototherapy (MP) was significantly the most effective in reduction of serum bilirubin level, while acupressure massage and phototherapy (AMP) was the least compared to by phototherapy only (P), with MD, 95%CI (-1.16 [-1.61; -0.72], 1.28 [0.79; 1.77] respectively). In 14th day of life, bilirubin level decreased the most in massage with enema and phototherapy (MEP), while MP has no significant difference compared to P. Our MA results in 4th day of life, indicated that MP had a significant decrease in bilirubin level compared with P, with MD 95%CI (-2.23 [-3.43; -1.03]). In summary comparison with P, MP was the most in decreasing bilirubin level in most of days, with the biggest decrease being in 4th day, while MEP was significantly the most in 14th day. For neonates not requiring PT, our NMA showed a significant decrease in bilirubin level with massage and bathing, acupressure massage, and massage 3–4 times/days (M2) groups in 3rd day of life, and with massage 1–2 times/days (M1) and M2 groups in 4th day. MEP group had a significantly longer duration of PT compared with P, with MD 95%CI (29.09 [9.76; 48.41]). M1 and M2 did not have a significant effect on the requirement for PT. Conclusion Massage therapy could be an effective adjuvant to PT in order to reduce the PT duration. However, it did not reduce the requirement for PT.

Hyperbolic metamaterials (HMMs) composed of multiple nanometal–dielectric films are proposed for launching deep subwavelength bulk plasmon polaritons (BPPs) as uniform, large area surface imaging illumination sources with a skin depth even beyond 10 nm. Benefiting from the coupled plasmon modes over a wide wavevector range in HMMs, the illumination depth could be continually tuned, simply by adjusting the incidence angle of light impinged on a grating structure for BPP excitation. As an example, the illumination depths of 19–63 nm at a light wavelength of 532 nm are demonstrated with SiO2–Ag multifilms. Moreover, the structure holds its deep subwavelength illumination depth for a broad light wavelength range, resembling that of light total internal reflection in a prism with an ultra high refractive index. Furthermore, a fluorescent nanoparticle based micro-zone system was employed for estimating the illumination depth of the HMM structure. The method is believed to provide access for surface imaging features in ultra thin layers especially for bio-samples.

In recent years, hyperlens technology has attracted more attention because of its function of magnification and demagnification. In this study, hyperlens demagnification imaging lithography was experimentally demonstrated with sub-diffraction resolution of about 55 nm line width and about 1.8 demagnification factor at 365 nm. The hyperlens was composed of multiple Ag/SiO2 films and combined with a resist layer and a plasmonic Ag reflector. It was employed to project mask patterns to subwavelength images for nanolithography. It was found that the plasmonic reflector contributes remarkably to improving imaging contrast, fidelity and efficiency by inhibiting the negative influences from the radial electric field components in the resist region. Furthermore, discussions about imaging influences with geometrical parameters are also presented.

The rapid development of online shopping offers new opportunities to the express delivery industry, but also brings enormous challenges due to its characteristics of multi-frequency and small-batch distribution. And the lack of cooperation among express companies in the urban distribution has resulted in uneconomical distribution. In the context of the sharing economy, this paper attempts to solve this problem by implementing joint distribution strategy with sharing the network resources. Based on the customer’s time window of receipt, a two-tier vehicle routing optimization model of urban joint distribution considering transfer stations’ sharing is established, and a hybrid heuristic algorithm has been designed accordingly. The results of a case study show significant optimization effect by comparing the independent distribution and joint distribution as well as robustness of the designed algorithm.

A plasmonic resonant cavity-based hyperlens is theoretically proposed and demonstrated to achieve far-field phase contrast images of nano-transparent objects. The phase contrast super-resolution imaging is mainly contributed to the excited surface plasmons inside hyperlens and cavity structure surrounding nano-objects, which help to greatly enhance evanescent waves generated by nano-transparent objects and convert weak phase information to light intensity distribution with high contrast at the zoomed imaging plane of hyperlens. As examples, nano-dielectric object imaging is numerically demonstrated with half-pitch resolution about lambda/10 and a minimum distinguishable refractive index difference down to 0.15.

Nanofabrication technology with high-resolution, high-throughput and low-cost is essential for the development of nanoplasmonic and nanophotonic devices. At present, most metasurfaces are fabricated in a point by point writing manner with electron beam lithography or a focused ion beam, which imposes a serious cost barrier with respect to practical applications. Near field optical lithography, seemingly providing a high-resolution and low-cost way, however, suffers from the ultra shallow depth and poor fidelity of obtained photoresist patterns due to the exponential decay feature of evanescent waves. Here, we propose a method of surface plasmonic imaging lithography by introducing a reflective plasmonic lens to amplify and compensate evanescent waves, resulting in the production of nano resist patterns with high fidelity, contrast and enhanced depth beyond that usually obtained by near field optical lithography. As examples, a discrete and anisotropically arrayed nano-slots mask pattern with different orientations and a size of 40 nm × 120 nm could be imaged in photoresist and transferred successfully onto a metal layer through an etching process. Evidence for the pattern quality is given by virtue of the fabricated metasurface lens devices showing good focusing performance in experiments. It is believed that this method provides a parallel, low-cost, high-throughput and large-area nanofabrication route for fabricating nanostructures of holograms, vortex phase plates, bio-sensors and solar cells etc.

In most sponsored search platforms, advertisers bid on some keywords for their advertisements (ads). Given a search request, ad retrieval module rewrites the query into bidding keywords, and uses these keywords as keys to select Top N ads through inverted indexes. In this way, an ad will not be retrieved even if queries are related when the advertiser does not bid on corresponding keywords. Moreover, most ad retrieval approaches regard rewriting and ad-selecting as two separated tasks, and focus on boosting relevance between search queries and ads. Recently, in e-commerce sponsored search more and more personalized information has been introduced, such as user profiles, long-time and real-time clicks. Personalized information makes ad retrieval able to employ more elements (e.g. real-time clicks) as search signals and retrieval keys, however it makes ad retrieval more difficult to measure ads retrieved through different signals. To address these problems, we propose a novel ad retrieval framework beyond keywords and relevance in e-commerce sponsored search. Firstly, we employ historical ad click data to initialize a hierarchical network representing signals, keys and ads, in which personalized information is introduced. Then we train a model on top of the hierarchical network by learning the weights of edges. Finally we select the best edges according to the model, boosting RPM/CTR. Experimental results on our e-commerce platform demonstrate that our ad retrieval framework achieves good performance.

Interference lithography based on surface plasmon polaritons has been proven to break the diffraction limit and deliver the high imaging resolution. However, most previously reported studies suffer from the inflexible pattern pitch for a certain structure ascribed to fixed excitation mode, which limits the applications in micro-/nano- fabrications. In this work, the large area deep subwavelength interference lithography with tunable pattern period based on bulk plasmon polaritons (BPPs) is proposed. By simply tuning the incident angle, the spatial frequencies of the selected BPPs modes squeezed through hyperbolic metamaterial changes correspondingly. As a result, the pitch of the interference pattern is continuously altered. The results demonstrate that one-dimensional and two-dimensional periodic patterns with pitch resolution ranging from 45 nm (~λ/10) to 115 nm (~λ/4) can be generated under 436 nm illumination. Additionally, the general method of designing such an interference lithography system is also discussed, which can be used for nanoscale fabrication in this fashion.