Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Lithography-based three-dimensional (3D) printing technologies allow high spatial resolution that exceeds that of typical extrusion-based bioprinting approaches, allowing to better mimic the complex architecture of biological tissues. Additionally, lithographic printing via digital light processing (DLP) enables fabrication of free-form lattice and patterned structures which cannot be easily produced with other 3D printing approaches. While significant progress has been dedicated to the development of cell-laden bioinks for extrusion-based bioprinting, less attention has been directed towards the development of cyto-compatible bio-resins and their application in lithography-based biofabrication, limiting the advancement of this promising technology. In this study, we developed a new bio-resin based on methacrylated poly(vinyl alcohol) (PVA-MA), gelatin-methacryloyl (Gel-MA) and a transition metal-based visible light photoinitiator. The utilization of a visible light photo-initiating system displaying high molar absorptivity allowed the bioprinting of constructs with high resolution features, in the range of 25-50 μm. Biofunctionalization of the resin with 1 wt% Gel-MA allowed long term survival (>90%) of encapsulated cells up to 21 d, and enabled attachment and spreading of endothelial cells seeded on the printed hydrogels. Cell-laden hydrogel constructs of high resolution with complex and ordered architecture were successfully bioprinted, where the encapsulated cells remained viable, homogenously distributed and functional. Bone and cartilage tissue synthesis was confirmed by encapsulated stem cells, underlining the potential of these DLP-bioprinted hydrogels for tissue engineering and biofabrication. Overall, the PVA-MA/Gel-MA bio-resin is a promising material for biofabrication and provides important cues for the further development of lithography-based bioprinting of complex, free-form living tissue analogues.

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Bio-resin for high resolution lithography-based biofabrication of complex cell-laden constructs

https://krishi.icar.gov.in/jspui/bitstream/123456789/28481/1/Nanotherapy_BIOPHA_2017.pdf

Nanotherapeutics: An insight into healthcare and multi-dimensional applications in medical sector of the modern world

Biophysical Regulation of Cell Behavior-Cross Talk between Substrate Stiffness and Nanotopography.

In order to accurately predict future states of a smart cyber-physical system, which can change its behavior to a large degree in response to environmental influences, the existence of precise models of the system and its surroundings is demandable. In machine engineering, ultra-high fidelity simulations have been developed to better understand both constraints in system design and possible consequences of external influences during the system's operation. These digital twins enable further applications in software design for complex cyber-physical systems as online planning methods can utilize good simulations to continuously optimize the system behavior, yielding a software architecture framework based on the information flow between the cyber-physical system, its physical environment and the digital twin model.

A Simulation-Based Architecture for Smart Cyber-Physical Systems

Although nanotopography has been shown to be a potent modulator of cell behavior, it is unclear how the nanotopographical cue, through focal adhesions, affects the nucleus, eventually influencing cell phenotype and function. Thus, current methods to apply nanotopography to regulate cell behavior are basically empirical. We, herein, engineered nanotopographies of various shapes (gratings and pillars) and dimensions (feature size, spacing and height), and thoroughly investigated cell spreading, focal adhesion organization and nuclear deformation of human primary fibroblasts as the model cell grown on the nanotopographies. We examined the correlation between nuclear deformation and cell functions such as cell proliferation, transfection and extracellular matrix protein type I collagen production. It was found that the nanoscale gratings and pillars could facilitate focal adhesion elongation by providing anchoring sites, and the nanogratings could orient focal adhesions and nuclei along the nanograting direct...

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Nanotopographical Modulation of Cell Function through Nuclear Deformation.

With general lighting applications being responsible for over 20% of the energy consumption in the United States, advances in solid-state lighting have the potential for considerable energy and cost savings. The United States Department of Energy predicts that the increased use of solid state lighting will result in a 46% lighting consumption energy savings by the year 2030. Smart lighting systems have the potential for reducing energy costs while also providing a means for short distance data transmission via free space optics. The group III-nitride (III-N) family of materials, including aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), their binary and ternary alloys, are uniquely situated to provide light emitting diodes (LEDs) across the full visible spectrum, photodetectors (PDs) and high power, high speed transistors. In this work, aluminum gallium nitride (AlGaN) / GaN high electron mobility transistors (HEMTs) and indium gallium nitride (InGaN) photodiodes (PDs) are fabricated and characterized. HEMTs and LEDs (or PDs) are grown on the same substrate for the purpose of creating electronic and optoelectronic integrated circuits.

Group III-Nitride Based Electronic and Optoelectronic Integrated Circuits for Smart Lighting Applications

Simulation-to-Flight 1 (STF-1): A Mission to Enable CubeSat Software-based Verification and Validation

We demonstrate a method to improve the light extraction from an LED using photonic crystal (PhC)-like structures in metal contacts. A patterned metal contact with an array of Silicon Oxide (SiOx) pillars (440 nm in size) on an InGaN/GaN-based MQW LED has shown to increase output illumination uniformity through experimental characterization. Structural methods of improving light extraction using transparent contacts or dielectric photonic crystals typically require a tradeoff between improving light extraction and optimal electrical characteristics. The method presented here provides an alternate solution to provide a 15% directional improvement (surface normal) in the radiation profile and ~ 30% increase in the respective intensity profile without affecting the electrical characteristics of the device. Electron beam patterning of hydrogen silesquioxane (HSQ), a novel electron beam resist is used in patterning these metal contacts. After patterning, thermal curing of the patterned resist is done to form SiOx pillars. These SiOx pillars aid as a mask for transferring the pattern to the p-metal contact. Electrical and optical characterization results of LEDs fabricated with and without patterned contacts are presented. We present the radiation and intensity profiles of the planar and patterned devices extracted using Matlab-based image analysis technique from 200 μm (diameter) circular unpackaged LEDs.

Improvement in the Light Extraction of Blue InGaN/GaN-Based LEDs Using Patterned Metal Contacts

Design, Fabrication and Characterization of Photonic Crystal Light-Emitting Diodes for Solid-State Lighting

Anand Kadiyala

Papers

Nanotopographical Modulation of Cell Function through Nuclear Deformation.

Group III-Nitride Based Electronic and Optoelectronic Integrated Circuits for Smart Lighting Applications

Simulation-to-Flight 1 (STF-1): A Mission to Enable CubeSat Software-based Verification and Validation

Improvement in the Light Extraction of Blue InGaN/GaN-Based LEDs Using Patterned Metal Contacts

Design, Fabrication and Characterization of Photonic Crystal Light-Emitting Diodes for Solid-State Lighting