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Abstract: Additive manufacturing is a highly effective and versatile technology, especially in the medical sector, due to its customization, material complexity, design flexibility, waste minimization, and ability to fabricate intricate shapes that are cumbersome to manufacture by conventional manufacturing techniques. 4D printing plays a significant role in the medical field, especially in the areas not covered by 3D printing technologies, such as smart implants, devices and tools. Also, 4D printing helps doctors to treat more patients with high accuracy and quality. Hence, this manuscript aims to provide an overview of distinct 3D and 4D printing techniques and their emerging applications in the medical sector. A study of 3D printing technologies is presented by explaining the working principles of distinct 3D printing methods: stereo lithography, fusion deposition modeling, inkjet printing, selective laser sintering, selective laser melting and electron beam melting. In addition, the emerging applications of 3D printing in medical sectors (e.g., bioprinting, surgical guides, pharmaceuticals, prostheses, medical devices, dentistry, physiotherapy, etc.), as well as challenges and the future scope of 3D printing, are also discussed. Further, the concept of 4D printing, the market for both 3D and 4D printing, the benefits of 4D printing, the comparison of 3D and 4D printing, limitations, applications, and the future scope of 4D printing in the medical sector are also covered.

Aims: This study aimed to investigate the molecular interactions of dextran as a solute with sodium hydroxide as a solvent. Background: The propagation of ultrasonic waves through solids and liquids offers vital information on the structure of solids and liquids. The molecular interaction in pure liquids and liquid solutions has also been explored using ultrasonic speed estimates. The ultrasonic speed in a fluid provides a cutting-edge, feasible, and trustworthy technique for examining the characteristics of the polymer, amino acid, carbohydrate, and vitamin arrangements, among other things. It is mainly connected to the binding capacities of particles or molecules and has been successfully used in comprehending the concept of molecular interaction in liquid solution. Ultrasonic velocity measurement allows for the precise evaluation of several relevant acoustical characteristics that are particularly sensitive to molecular interactions. Objective: The acoustic and thermodynamic characteristics were utilised to investigate different types of interactions, molecular motion, and different interaction modes and their effects, which were impacted by the size of the pure component and the mixes. The significance provides subjective data on the nature and quality of particle interactions between solute and solvent in liquid solutions. Acoustic characteristics are important for evaluating the effect of temperature and frequency on the polymer dextran's aqueous sodium hydroxide solvent interactions. The density (ρ), viscosity, and ultrasonic speed (η) at 303 K, 308K, 313 K, 318K and 323K have been measured in the systems of polymer dextran with aqueous sodium hydroxide solution by using a pycnometer, Ostwald viscometer, and ultrasonic interferometer at frequencies at 1MHz, 5MHz, 9MHz, 12MHz, respectively. The acoustic parameters, such as free volume, internal pressure, attenuation coefficient, Rao’s constant, and Wada’s constant, are determined using the experimental parameters, including density (ρ), viscosity (η), and ultrasonic speed (U). Methods: In this study, a pycnometer, an Ostwald's viscometer, and an ultrasonic interferometer to measure the density, viscosity, and ultrasonic velocity of the solution and compute the thermoacoustic parameters based on the measured parameters were used. Results: Ultrasonic wave propagation affects the physical characteristics of the medium, providing information about liquid and solution Conclusion: The effect of frequency and temperature on thermo-acoustic properties was studied. The aforementioned research has interpreted the nature of forces between molecules, such as hydrogen bonds, charge transfer complexes, and the breakdown of hydrogen bonds and complexes. Intermolecular forces are weak (electrostatic forces between charged particles having a permanent dipole and molecules with induced dipoles). The geometrical fitting of one molecule into another, owing to the variation in shape and size of the molecules, results in structural properties of the components. Other: In recent years, advances in ultrasonic methods have made them a potent instrument for assessing knowledge about the physical and chemical behaviour of liquid molecules. Due to its versatile pharmaceutical, biological, and contemporary uses, it has drawn analysts' attention to a new area of investigation. Consistent data on the physical and chemical characteristics of a wide range of liquid solutions are required.

Abstract: Recently, rare-earth activated phosphors have gained new and exciting applications in various fields, like display and illumination, phototherapy, plant growth, etc. The phosphorconverted white light emitting diode is prime in the art of solid-state lighting owing to its numerous merits, including desired spectral distribution, excellent chemical and thermal stability, high operational lifetime, reliability, and color quality of w-LEDs for lighting. The enhancement of the color gamut of backlight w-LEDs still needs to be addressed, which requires the design of high-efficient downshifting converter phosphors featuring thermally stable luminescence. The class of materials under suitable activation exhibit applications in a particular field. The emission in the UV region (312-315nm) is widely used for phototherapy lamps. Phototherapy has proven to be an excellent therapeutic option for the treatment of various types of skin diseases. Moreover, the emission corresponds to 600-750nm for plant cultivation. The present review article describes various rare-earth activated phosphors and their impact on human and plant physiology.