The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip. The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits, giving rise to numerous meta-waveguides with unprecedented strength in controlling guided electromagnetic waves. Here, we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms, such as dielectric or plasmonic waveguides and optical fibers. Foundational results and representative applications are comprehensively summarized. Brief physical models with explicit design tutorials, either physical intuition-based design methods or computer algorithms-based inverse designs, are cataloged as well. We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems, by enhancing light-matter interaction strength to drastically boost device performance, or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities. We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits, biomedical sensing, artificial intelligence and beyond.

Stretchable electrodes are playing important roles in the measurement of bio‐electrical signals especially in wearable electronic devices. These electrodes usually adopt commercial elastomers such as polydimethylsiloxane or polystyrene‐ethylene‐butylene‐styrene as substrates, which result in poor stability and reliability due to weak interfacial adhesion between electrodes and human skin. Here, dopamine is introduced into the hydrogen bonding based elastomer as pendent groups. The elastomer shows both mechanical strength and adhesion strength at the same time. It exhibits high stress at break (1.9 MPa) and high fracture strain (5100%). Significantly, it exhibits a high adhesive strength (≈62 kPa) and underwater adhesive strength (≈16 kPa) with epithelial tissue. Thus, a stretchable bio‐interfacial electrode is fabricated by spray‐coating silver nanowires on the elastic substrate, which is stretchable, self‐healable, and highly adhesive and suitable for electromyogram measurement.

Sirtuin 2 (SIRT2) is a member of the sirtuin family of NAD + -dependent protein deacetylases. In recent years, SIRT2 inhibition has emerged as a promising treatment for neurodegenerative diseases. However, to date, there is no evidence of a specific role for SIRT2 in traumatic brain injury (TBI). We investigated the effects of SIRT2 inhibition on experimental TBI using the controlled cortical impact (CCI) injury model. Adult male mice underwent CCI or sham surgery. A selective brain-permeable SIRT2 inhibitor, AK-7, was administrated 30 min before injury. The volume of the brain edema lesion and the water content of the brain were significantly increased in mice treated with AK-7 (20 mg/kg), compared with the vehicle group, following TBI (p < 0.05 at 1 day and p < 0.05 at 3 days, respectively). Concomitantly, AK-7 administration greatly worsened neurobehavioral deficits on days 3 and 7 after CCI. Furthermore, blood-brain barrier disruption and matrix metalloproteinases (MMP)-9 activity increased following SIRT2 inhibition. AK-7 treatment increased TBI-induced microglial activation both in vivo and in vitro, accompanied by a large increase in the expression and release of inflammatory cytokines. Mechanistically, SIRT2 inhibition increased both K310 acetylation and nuclear translocation of NF-jB p65, leading to enhanced NF-jB activation and up-regulation of its target genes, including aquaporin 4 (AQP4), MMP-9, and proinflammatory cytokines. Together, these data demonstrate that SIRT2 inhibition exacerbates TBI by increasing NF-jB p65 acetylation and activation. Our findings provide additional evidence of an anti-inflammatory effect of SIRT2. Keywords: blood-brain barrier, cerebral edema, inflammation, SIRT2, traumatic brain injury. Traumatic brain injury (TBI) involves a primary insult that occurs at the moment of impact that initiates subsequent physiological and pathological reactions that may last for days to months (Masel and DeWitt 2010). Despite recent advances in the understanding of the pathological process of TBI, an effective treatment that prevents or repairs TBI-induced loss-of-function remains to be discovered.

BackgroundRecent reports support a novel biological phenomenon about cancer related neurogenesis. However, little is known about the clinicopathological significance of neurogenesis in breast cancer.MethodsA total of 196 cases, including 20 of normal tissue, 14 of fibroadenoma, 18 of ductal carcinoma in situ (DCIS) and 144 of invasive ductal carcinoma (IDC) of the breast were used. The tissue slides were immunostained for protein gene product (PGP) 9.5 and S 100 to identify nerves. The correlation between the expression of PGP 9.5 and clinicopathological characteristics in IDC of the breast was assessed.ResultsWhile the PGP 9.5 positive nerve fibers are identified in all cases of normal breast tissue controls and in the tumor stroma of 61% (89/144) cases of invasive ductal carcinomas, PGP 9.5 positive nerve fibers are not seen in the tumor stroma of cases of fibroadenoma and DCIS. The percentage of tumors that exhibited neurogenesis increased from tumor grade I to tumor grade II and III (29.4% vs 71.8%, p < 0.0001). In addition, patients with less than 3 years of disease-free survival tended to have a higher positive expression of PGP 9.5 compared to patients with an equal or more than 3 years of disease-free survival (64.8% vs 46.7%, p = 0.035). Furthermore, moderate/strong expression of PGP 9.5 was found to be significantly related to microvessel density (MVD, p = 0.014). Interestingly, PGP 9.5 expression was significantly associated with higher MVD in the ER-negative (p = 0.045) and node-negative (p = 0.039) subgroups of IDC of the breast.ConclusionsThis data indicates that neurogenesis is associated with some aggressive features of IDC including tumor grade and patient survival as well as angiogenesis, especially in ER-negative and node-negative subtypes of IDC of the breast. Thus, neurogenesis appears to be associated with breast cancer progression and may play a role in therapeutic guidance for patients with ER-negative and node-negative invasive breast cancer.

Randomly oriented fiber mats and well-aligned fiber bundles of the biodegradable polylactide (PLA)/ poly(ε-caprolactone) (PCL) blends were successfully produced by electrospinning in the present study. For the reticulate fibers, the effects of the blending ratio of two polymers and compositions of mixed solvents on fiber morphology were investigated. The results reveal that the fibers with lower PCL mass fraction show better morphology with larger average fiber diameter than those of the fibers with higher PCL mass fraction. Besides, a small addition of dimethylformamide (DMF) as the assistant solvent favors further improvement of fiber morphology because of the synergistic effects by improved conductivity and altered viscosity of the electrospun solutions. Although the as-obtained blend fibers show smooth surface structure, the phase separation between PCL and PLA occurs inside the fibers because the two components are thermodynamically immiscible, and the discrete phase shows an elongated morphology along with the fiber axis, instead of the droplet structure. For the aligned fiber bundles collected on a rotating disk, the degree of order increases with increase of the tangential velocity, accompanied by reduced average fiber diameter. Hierarchical orientations including the macroscopic fiber alignment, the elongation of discrete PCL phase, and the molecular orientation of both the PLA and PCL can be observed within the aligned blend fibers.

A high-efficiency inverse design of “digital” subwavelength nanophotonic devices using the adjoint method is proposed. We design a single-mode 3 dB power divider and a dual-mode demultiplexer to demonstrate the efficiency of the proposed inverse design approach, called the digitized adjoint method, for single- and dual-object optimization, respectively. The optimization comprises three stages: 1) continuous variation for an “analog” pattern; 2) forced permittivity biasing for a “quasi-digital” pattern; and 3) a multilevel digital pattern. Compared with the conventional brute-force method, the proposed method can improve design efficiency by about five times, and the performance optimization can reach approximately the same level. The method takes advantages of adjoint sensitivity analysis and digital subwavelength structure and creates a new way for the efficient and high-performance design of compact digital subwavelength nanophotonic devices, which could overcome the efficiency bottleneck of the brute-force method, which is restricted by the number of pixels of a digital pattern, and improve the device performance by extending a conventional binary pattern to a multilevel one.

Background. This study aimed to evaluate the usability of SWI in assessment of brain iron to detect cognitive dysfunction in patients with chronic mild traumatic brain injury (mTBI). Methods. 39 patients with mTBI and 37 normal controls were given the Mini-Mental State Examination (MMSE) and underwent SWI scanning at least 6 months after injury. Angle radian values were calculated with phase images. The angle radian values were compared between groups using analysis of covariance, and their association with MMSE scores was analyzed using Spearman correlations. Results. Significantly higher angle radian values (p < 0.05) were found in the head of the caudate nucleus, the lenticular nucleus, the hippocampus, the thalamus, the right substantia nigra, the red nucleus, and the splenium of the corpus callosum (SCC) in the mTBI group, compared to the control group. MMSE scores were negatively correlated with angle radian values in the right substantia nigra (r = −0.685, p < 0.001). Conclusions. Patients with chronic mTBI might have abnormally high accumulations of iron, and their MMSE scores are negatively associated with angle radian values in the right substantia nigra, suggesting a role of SWI in the assessment of cognitive impairments of these patients.

We propose and experimentally demonstrate a novel ultracompact multimode waveguide crossing. The compact asymmetric subwavelength Y-junction is introduced to convert the high-order modes into fundamental ones, enabling one to implement three or more modes simultaneously in the subsequent processing. Our proposed device occupied only a compact footprint of 34 × 34 µm 2 . The measured results indicate our fabricated device exhibited a high performance with the insertion loss less than 0.9 dB, crosstalk lower than -24 dB from 1.52 to 1.60 µm for all the three modes. Moreover, our scheme could be easily expended to implement more modes and will show great potential in dense and large-scale on-chip photonic integration.