Sohail F. Shaikh

Design criteria for XeF2 enabled deterministic transformation of bulk silicon (100) into flexible silicon layer

Isotropic etching of bulk silicon (100) using Xenon Difluoride (XeF2) gas presents a unique opportunity to undercut and release ultra-thin flexible silicon layers with pre-fabricated state-of-the-art Complementary Metal Oxide Semiconductor (CMOS) electronics. In this work, we present design criteria and mechanism with a comprehensive mathematical model for this method. We consider various trench geometries and parametrize important metrics such as etch time, number of cycles and area efficiency in terms of the trench diameter and spacing so that optimization can be done for specific applications. From our theoretical analysis, we conclude that a honeycomb-inspired hexagonal distribution of trenches can produce the most efficient release of ultra-thin flexible silicon layers in terms of the number of etch cycles, while a rectangular distribution of circular trenches provides the most area efficient design. The theoretical results are verified by fabricating and releasing (varying sizes) flexible silicon la...

Freeform Compliant CMOS Electronic Systems for Internet of Everything Applications

The state-of-the-art electronics technology has been an integral part of modern advances. The prevalent rise of the mobile device and computational technology in the age of information technology offers exciting applications that are attributed to sophisticated, enormously reliable, and most mature CMOS-based electronics. We are accustomed to high performance, cost-effective, multifunctional, and energy-efficient scaled electronics. However, they are rigid, bulky, and brittle. The convolution of flexibility and stretchability in electronics for emerging Internet of Everything application can unleash smart application horizon in unexplored areas, such as robotics, healthcare, smart cities, transport, and entertainment systems. While flexible and stretchable device themes are being remarkably chased, the realization of the fully compliant electronic system is unaddressed. Integration of data processing, storage, communication, and energy management devices complements a compliant system. Here, a comprehensive review is presented on necessity and design criteria for freeform (physically flexible and stretchable) compliant high-performance CMOS electronic systems.

Compliant lightweight non-invasive standalone “Marine Skin” tagging system

Current marine research primarily depends on weighty and invasive sensory equipment and telemetric network to understand the marine environment, including the diverse fauna it contains, as a function of animal behavior and size, as well as equipment longevity. To match animal morphology and activity within the surrounding marine environment, here we show a physically flexible and stretchable skin-like and waterproof autonomous multifunctional system, integrating Bluetooth, memory chip, and high performance physical sensors. The sensory tag is mounted on a swimming crab (Portunus pelagicus) and is capable of continuous logging of depth, temperature, and salinity within the harsh ocean environment. The fully packaged, ultra-lightweight (<2.4 g in water), and compliant “Marine Skin” system does not have any wired connection enabling safe and weightless cutting-edge approach to monitor and assess marine life and the ecosystem’s health to support conservation and management of marine ecosystems.Marine sensory tags: a non-invasive solutionA cost-effective multi-sensory tag system has been developed by integrating wireless communication, high performance physical sensors and conformal packaging for marine research. A collaborative team led by Prof Muhammad Hussain from King Abdullah University of Science and Technology, Saudi Arabia designs a non-invasive, wireless, lightweight epidermal multisensory tag with long deployment lifetime for marine research applications. To show the non-invasive and lightweight features of the “Marine Skin” tags, they test their long term temperature, pressure, salinity and their cross-sensitivity on the crustaceans in Red Sea water for more than 20 days. The sensory tags can be tailored for a diversity of animals of irregular size and shape due to the non-invasiveness and conformality of the functional circuits and packaging materials. They enable cost-effective solutions for long term monitoring and measuring.

Contact resistance reduction of ZnO thin film transistors (TFTs) with saw-shaped electrode

We report on a saw-shaped electrode architecture ZnO thin film transistor (TFT), which effectively increases the channel width. The contact line of the saw-shaped electrode is almost twice as long at the contact metal/ZnO channel junction. We experimentally observed an enhancement in the output drive current by 50% and a reduction in the contact resistance by over 50%, when compared to a typically shaped electrode ZnO TFT consuming the same chip area. This performance enhancement is attributed to the extension of the channel width. This technique can contribute to device performance enhancement, and in particular reduce the contact resistance, which is a serious challenge.

Fully spherical stretchable silicon photodiodes array for simultaneous 360 imaging

Imaging is one of the important wonders of todays world. While everyday millions of snaps are taken, new advances like panoramic imaging have become increasingly popular. However, as of today an imaging system which can simultaneously capture images from all 360° viewpoints with a single sensor has not been achieved. Here, we show a physically flexible and stretchable version of arrayed silicon photodiodes made from low-cost bulk monocrystalline silicon (100) that can capture simultaneous omnidirectional images. The present report, with multiple wavelength detection, fast photoresponsivity, a wide viewing angle, selective aberration, and dynamic focusing enabled by 3D printed pneumatic actuators (note, today millions of image sensors can be integrated in mm2 area), overcomes previous demonstrations of only hemispherical photodetection capability. Such imaging capability will make unmanned air vehicles or self-driven cars safer, affordable augmented and virtual reality and more importantly, in-vivo biomedical imaging will be more effective.Imaging is one of the important wonders of todays world. While everyday millions of snaps are taken, new advances like panoramic imaging have become increasingly popular. However, as of today an imaging system which can simultaneously capture images from all 360° viewpoints with a single sensor has not been achieved. Here, we show a physically flexible and stretchable version of arrayed silicon photodiodes made from low-cost bulk monocrystalline silicon (100) that can capture simultaneous omnidirectional images. The present report, with multiple wavelength detection, fast photoresponsivity, a wide viewing angle, selective aberration, and dynamic focusing enabled by 3D printed pneumatic actuators (note, today millions of image sensors can be integrated in mm2 area), overcomes previous demonstrations of only hemispherical photodetection capability. Such imaging capability will make unmanned air vehicles or self-driven cars safer, affordable augmented and virtual reality and more importantly, in-vivo biomed...