Dynamics and phase behavior of metallo-dielectric rod-shaped microswimmers driven by alternating current electric field.

The ability to move and self-organize in response to external stimuli is a fascinating feature of living active matter. Here, the metallo-dielectric rod-shaped microswimmers are shown to have a similar behavior in the presence of an AC electric field. The silica-copper Janus microrods were fabricated using the physical vapor deposition-based glancing angle deposition technique (GLAD). When the aqueous solution of the microrods was under the influence of an external AC electric field, they were found to exhibit different phases such as clustering, swimming, and vertical standing in response to variation of the applied frequency. The swimming behavior (5-90 kHz) of the rods is attributed to the induced-charge electrophoresis (ICEP) phenomenon, whereas the dynamic clustering (<5 kHz) could be explained in terms of the electrohydrodynamic (EHD) interaction. Interestingly, the rods flip to attain the vertically standing position when responding to the applied electric field above 90 kHz. The reorientation and switching of the major axis of the rod along the field direction is attributed to the electro-orientation phenomenon. This is basically due to the dominance of the electric torque above the upper limit of the characteristic frequency, where the strength of slip flows around the microrods is predicted to be poor. The present study not only offers insight into the fundamental aspects of the dynamics and the phase behavior of rod-shaped microswimmers, but also opens an avenue to design reconfigurable active matter systems with features inspired by biological systems.

Significance of peripheral eosinophilia for diagnosis of IgG4-related disease in subjects with elevated serum IgG4 levels.

OBJECTIVES: In this study, we aim to assess the diagnostic utility of elevated serum IgG4 (sIgG4) concentration alone and in combination with peripheral eosinophilia (PE) for IgG4-related disease (IgG4-RD). METHODS: From the Mayo Clinic, Rochester electronic medical record database we identified 409 patients with above normal levels of sIgG4 (reference range 121-140 mg/dL) who had sIgG4 measured to differentiate IgG4-RD from another disease. RESULTS: Among 409 patients with any elevation in sIgG4 levels, 129 (31.5%) had a definite diagnosis of IgG4-RD. The prevalence of PE increased with increasing sIgG4 levels and was more likely to be seen in subjects with IgG4-RD vs. non-IgG4-RD at ≥1X (n = 35/120, 29.2% vs. n = 23/258, 8.9%; p < 0.001), ≥2X (n = 23/64, 35.9% vs. n = 5/54,9.3%; p = 0.001) and ≥3X (n = 18/42, 42.9% vs. n = 0/9, 0%; p = 0.015) of sIgG4 upper limit of normal (ULN), respectively. After adjusting for gender and age, sIgG4 levels ≥ 2X ULN with PE as a predictor, had a higher positive predictive value in predicting IgG4-RD (72.2% vs. 65.9%) with an Area Under the Receiver Operatic Characteristic Curve (AUC) of 0.776, compared to sIgG4 ≥ 2X ULN without PE predictor (AUC = 0.74), p = 0.016. PE, sIgG4≥2X ULN, male gender, and age independently predicted the disease with odds ratio of 4.89 (95% CI:2.51-9.54), 3.78 (95% CI:2.27-6.28), 2.78 (95% CI:1.55-4.97), and 1.03 (95% CI:1.02-1.05), respectively. CONCLUSION: Even in subjects in whom IgG4-RD is suspected, only a minority (∼30%) with elevated sIgG4 levels have IgG4-RD. sIgG4 by itself is more specific at higher levels, though never diagnostic. PE increases with increasing sIgG4 and adds diagnostic value at higher sIgG4 levels.

Computerized tomography scan in pre-diagnostic pancreatic ductal adenocarcinoma: Stages of progression and potential benefits of early intervention: A retrospective study.

BACKGROUND: The frequency, nature and timeline of changes on thin-slice (≤3 mm) multi-detector computerized tomography (CT) scans in the pre-diagnostic phase of pancreatic ductal adenocarcinoma (PDAC) are unknown. It is unclear if identifying imaging changes in this phase will improve PDAC survival beyond lead time. METHODS: From a cohort of 128 subjects (Cohort A) with CT scans done 3-36 months before diagnosis of PDAC we developed a CTgram defining CT Stages (CTS) I through IV in the radiological progression of pre-diagnostic PDAC. We constructed Cohort B of PDAC resected at CTS I and II and compared survival in CTS I and II in Cohort A (n = 22 each; control natural history cohort) vs Cohort B (n = 33 and 72, respectively; early interception cohort). RESULTS: CTs were abnormal in 16% and 85% at 24-36 and 3-6 months respectively, before PDAC diagnosis. The PDAC CTgram stages, findings and median lead times (months) to clinical diagnosis were: CTS I: Abrupt duct cut-off/duct dilatation (-12.8); CTS II: Low density mass confined to pancreas (-9.5), CTS III: Peri-pancreatic infiltration (-5.8), CTS IV: Distant metastases (only at diagnosis). PDAC survival was better in cohort B than in cohort A despite inclusion of lead time in Cohort A: CTS I (36 vs 17.2 months, p = 0.03), CTS II (35.2 vs 15.3 months, p = 0.04). CONCLUSION: Starting 12-18 months before PDAC diagnosis, progressive and increasingly frequent changes occur on CT scans. Resection of PDAC at the time of pre-diagnostic CT changes is likely to provide survival benefit beyond lead time.

Beyond O&P Times Three.

Although examination of the stool for ova and parasites times three (O&P ×3) is routinely performed in the United States (US) for the evaluation of persistent and/or chronic diarrhea, the result is almost always negative. This has contributed to the perception that parasitic diseases are nearly non-existent in the country unless there is a history of travel to an endemic area. The increasing number of immigrants from third-world countries, tourists, and students who present with symptoms of parasitic diseases are often misdiagnosed as having irritable bowel syndrome or inflammatory bowel disease. The consequences of such misdiagnosis need no explanation. However, certain parasitic diseases are endemic to the US and other developed nations and affect both immunocompetent and immunocompromised patients. Testing for parasitic diseases either with O&P or with other diagnostic tests, followed by the recommended treatment, is quite rewarding when appropriate. Most parasitic diseases are easily treatable and should not be confused with other chronic gastrointestinal (GI) disorders. In this review, we critically evaluate the symptomatology of luminal parasitic diseases, their differential diagnoses, appropriate diagnostic tests, and management.

Chiral Plasmonic Hydrogen Sensors.

In this article, a chiral plasmonic hydrogen-sensing platform using palladium-based nanohelices is demonstrated. Such 3D chiral nanostructures fabricated by nanoglancing angle deposition exhibit strong circular dichroism both experimentally and theoretically. The chiroptical properties of the palladium nanohelices are altered upon hydrogen uptake and sensitively depend on the hydrogen concentration. Such properties are well suited for remote and spark-free hydrogen sensing in the flammable range. Hysteresis is reduced, when an increasing amount of gold is utilized in the palladium-gold hybrid helices. As a result, the linearity of the circular dichroism in response to hydrogen is significantly improved. The chiral plasmonic sensor scheme is of potential interest for hydrogen-sensing applications, where good linearity and high sensitivity are required.

Spatially graded TiO2-SiO2 Bragg reflector with rainbow-colored photonic band gap.

A simple single-step method to fabricate spatially graded TiO2-SiO2 Bragg stack with rainbow colored photonic band gap is presented. The gradation in thickness of the Bragg stack was accomplished with a modified glancing angle deposition (GLAD) technique with dynamic shadow enabled by a block attached to one edge of the rotating substrate. A linear gradation in thickness over a distance of about 17 mm resulted in a brilliant colorful rainbow pattern. Interestingly, the photonic band gap position can be changed across the whole visible wavelength range by linearly translating the graded Bragg stack over a large area substrate. The spatially graded Bragg stack may find potential applications in the tunable optical devices, such as optical filters, reflection gratings, and lasers.

Light-driven micromotors for on-demand and local pH sensing applications.

In recent years, self-propelled light-driven micromotors have gained significant attention due to their capabilities for a wide range of applications, including cargo delivery, chemical sensing, environmental monitoring, etc. Here, we demonstrate the design of light-driven micromotors for local pH sensing applications. The micromotors are spherical Janus particles with multiple functional coatings that provide them with interesting features, like a dual optical response, i.e., controlled swimming under UV light (320-400 nm) and pH-dependent fluorescence signal emission when excited with blue light (450 nm), and moving path guidance using a weak external uniform magnetic field (50 G). All of these features allow the micromotors to sense the pH of the medium on-demand and locally or of a target location by guiding them to swim to the target location. The pH-dependent change in the fluorescence signal intensity is used for the measurement of the local pH of the medium. It is observed that the careful measurement of small pH changes requires a spectrometer that precisely measures the intensity change. However, the fluorescence signal of the micromotors was good enough to provide a clear visual demarcation for large pH changes. Systematic experimental studies supported by controlled experiments are performed to optimize the system as well as to calibrate the micromotors for local pH sensing applications. The characteristics like easy-to-design structure, light activation, directional swimming, and ability to measure the pH on-demand and locally prove that micromotors have the potential to revolutionize pH monitoring in various domains, including lab-on-a-chip devices, biomedical research, environmental monitoring, quality control in industrial processes, etc.

pH-Responsive swimming behavior of light-powered rod-shaped micromotors.

Micromotors have emerged as promising devices for a wide range of applications e.g., microfluidics, lab-on-a-chip devices, active matter, environmental monitoring, etc. The control over the activity of micromotors with the ability to exhibit multimode swimming is one of the most desirable features for many of the applications. Here, we demonstrate a rod-shaped light-driven micromotor whose activity and swimming behavior can easily be controlled. The rod-shaped micromotors are fabricated through the dynamic shadowing growth (DSG) technique, where a 2 µm long arm of titanium dioxide (TiO2) is grown over spherical silica (SiO2) particles (1 µm diameter). Under low-intensity UV light exposure, the micromotors exhibit self-propulsion in an aqueous peroxide medium. When activated, the swimming behavior of micromotors greatly depends on the pH of the medium. The swimming direction, i.e., forward or backward movement, as well as swimming modes like translational or rotational motion, can be controlled by changing the pH values. The observed dynamics has been rationalized using a theoretical model incorporating chemical activity, hydrodynamic flow, and the effect of gravity for a rod-shaped active particle near a planar wall. The pH-dependent translational and rotational dynamics of micromotors provide a versatile platform for achieving controlled and responsive behaviors. Continued research and development in this area hold great promise for advancing micromotors and enabling novel applications in microfluidics, micromachining, environmental sciences, and biomedicine.

Light-driven microrobots: capture and transport of bacteria and microparticles in a fluid medium.

The design of simple microrobotic systems with capabilities to address various applications like cargo transportation, as well as biological sample capture and manipulation in an individual unit, provides a novel route for designing advanced multifunctional microscale systems. Here, we demonstrate a facile approach to fabricate such multifunctional and fully controlled light-driven microrobots. The microrobots are titanium dioxide-silica Janus particles that are propelled in aqueous hydroquinone/benzoquinone fuel when illuminated by low-intensity UV light. The application of light provides control over the speed as well as activity of the microrobots. When modified with additional thin film coatings of nickel and gold, the microrobots exhibit the capturing and transportation of silica microparticles and E. coli bacteria. While transporting, they also show guided swimming under an external uniform magnetic field, which is interesting for deciding their moving path or the start/end positions. The fluorescent dye-based live/dead tests confirm that in the microrobot system almost no bacteria were harmed during the capturing or transportation. The simplistic design and steerable swimming with the ability to capture and transport are the important features of the microrobots. These features make them an ideal candidate for in vitro or lab-on-a-chip based studies, e.g., drug delivery, bacterial sensing, cell treatment, etc., where the capturing and transport of microscopic entities play a crucial role.

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film.

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses.