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.

Leveraging metal node-linker self-assembly to access functional anisotropy of zirconium-based MOF-on-MOF epitaxial heterostructure thin films.

Chemically robust, functional porous materials are imperative for designing novel membranes for chemical separation and heterogeneous catalysts. Among the array of potential materials, zirconium (Zr)-based metal-organic frameworks (MOFs) have garnered considerable attention, and have been investigated for applications related to gas separation and storage, and catalysis. However, a significant challenge with Zr-MOFs lies in their processibility, particularly in achieving homogenous thin films and controlling functional anisotropy. The recent developments in MOF thin film fabrication methodologies do not yield a solution to achieve mild reaction condition growth of Zr-MOF thin films with epitaxial MOF-on-MOF geometry (i.e. functional anisotropy). In the current work, we have devised a straightforward methodology under room temperature conditions, which enables epitaxial, oriented MOF-on-MOF thin film growth. This achievement is accomplished through a stepwise self-assembly approach involving Zr nodes and linkers on a functionalized substrate. This de novo developed strategy of functionality design is demonstrated for UiO-66 (University of Oslo) type Zr-MOFs. We have demonstrated the precise placement of chemical functionalities within the thin film structure, allowing for controlled chemical diffusion and regulation of diffusion selectivity.

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.

Left main coronary artery aneurysm with fistula to superior vena cava: A challenging case.

Coronary artery fistulas (CAFs) are rare congenital coronary artery abnormalities, with direct communication between a coronary artery and a cardiac chamber, great vessel or other structure. We report here, a rare case of a 25-year-old male with CAF from the aneurysmal left main coronary artery to the superior vena cava detected on echocardiography and computerized tomography (CT) coronary angiography.

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.

Comparative study of intranasal dexmedetomidine v/s midazolam for sedation of pediatric patients during transthoracic echocardiography.

Background: Procedural sedation required to improve the quality of Transthoracic Echocardiography (TTE) in infants and children. The ideal drug and route for sedation in children should have a rapid and reliable onset, atraumatic, palatable with minimal side effects, and rapid recovery. So, the aim of our study to evaluate and compare the efficacy and safety of intranasal midazolam and intranasal dexmedetomidine in pediatric patients for sedation during TTE. Materials and Method: Hundred children under three year of age, belonging to the American Society of Anaesthesiologists class-I and II, scheduled for TTE were divided into two groups by standard randomization technique. Patients in group-M received intranasal midazolam 0.2 mg/kg, whereas patients in group-D received intranasal dexmedetomidine 2 µg/kg prior to TTE under an adequately monitored anesthesia care. Onset and duration of sedation, heart rate, oxygen saturation, sonographer's, and parent's satisfaction scores were recorded. Results: All patients were successfully sedated for TTE. The average onset time, sedation time, awakening time and total time for Group-M were 7.3, 18.8, 29.51, 51 min and group-D were 10.1, 14.2, 24.9, 46.3 min, respectively and all were statistically significant (P < 0.001). TTE scan time of Group-M is 8.84 min and Group-D is 9.18 min and was statistically significant. Sonographer's and Parent's average satisfaction score for Group-M was 9.88, 10 and for Group-D was 7.64, 8.76, respectively, which were statistically significant (P < 0.001). Conclusion: Intranasal midazolam and dexmedetomidine are safe and effective for sedation in TTE. Intranasal midazolam was found to be comparatively more effective in view of onset of action, sonographers, and parental satisfaction score, while sedation time, awakening time and total duration was significantly higher as compared to intranasal dexmedetomidine.

Anesthetic and intensive care management of left main coronary artery to main pulmonary artery fistula diagnosed in postoperative case of tetralogy of fallot.

Cases of coronary to pulmonary artery fistula are seen in patients of pulmonary atresia with ventricular septal defect (VSD). These fistulas are rarely seen in patients of Tetralogy of Fallot (TOF). In this case report, we have presented ICU management of a postoperative case of TOF, with missed diagnosis of left main coronary artery (LMCA) to main pulmonary artery (MPA) fistula.