Recent Submissions

  • Toward nanotechnology-enabled face masks against SARS-CoV-2 and pandemic respiratory diseases.

    Elatab, Nazek; Mishra, R. B.; Hussain, Muhammad Mustafa (Nanotechnology, IOP Publishing, 2021-11-02) [Article]
    Wearing a face mask has become a necessity following the outbreak of the coronavirus (COVID-19) disease, where its effectiveness in containing the pandemic has been confirmed. Nevertheless, the pandemic has revealed major deficiencies in the ability to manufacture and ramp up worldwide production of efficient surgical-grade face masks. As a result, many researchers have focused their efforts on the development of low cost, smart and effective face covers. In this article, following a short introduction concerning face mask requirements, the different nanotechnology-enabled techniques for achieving better protection against the SARS-CoV-2 virus are reviewed, including the development of nanoporous and nanofibrous membranes in addition to triboelectric nanogenerators based masks, which can filter the virus using various mechanisms such as straining, electrostatic attraction and electrocution. The development of nanomaterials-based mask coatings to achieve virus repellent and sterilizing capabilities, including antiviral, hydrophobic and photothermal features are also discussed. Finally, the usability of nanotechnology-enabled face masks is discussed and compared with that of current commercial-grade N95 masks. To conclude, we highlight the challenges associated with the quick transfer of nanomaterials-enabled face masks and provide an overall outlook of the importance of nanotechnology in counteracting the COVID-19 and future pandemics.
  • Solar Powered Small Unmanned Aerial Vehicles: A Review

    Elatab, Nazek; Mishra, Rishabh B.; Alshanbari, Reem; Hussain, Muhammad Mustafa (Energy Technology, Wiley, 2021-10-27) [Article]
    In recent years, there has been an increasing demand for unmanned aerial vehicles (UAVs) with various capabilities suitable for both military and civilian applications. There is also a substantial interest in the development of novel drones that can fly autonomously in different environments and locations and perform various missions. Nevertheless, current battery-powered UAVs are limited by their flight range. Consequently, several approaches are being developed to enhance the flight endurance of drones, including augmenting the drone with solar power. In this review paper, we identify the different classifications of drones that have been developed based on their weight and flight range. Then, we explain the design challenges of the electrical systems embedded in the flying drones. Next, we discuss in detail approaches used to increase the flight endurance using various types of solar cells with respect to their materials and mechanical flexibility, in addition to various navigation and control approaches. Finally, limitations of existing solar-powered UAVs are presented in addition to proposed solutions and recommendations for the next generation of drones.
  • Wrinkled Polydimethylsiloxane for Enhanced Light Trapping and Anti-Reflection in Flexible Corrugated Silicon Solar Cells

    Elatab, Nazek; Babatain, Wedyan; Hussain, Muhammad Mustafa (IEEE, 2021-08-26) [Conference Paper]
    Light trapping and anti-reflection schemes serve a key role in reducing light reflection and enhancing absorption within solar cells. Here, we demonstrate the use of polydimethylsiloxane (PDMS) for enhancing light confinement in flexible corrugated c-silicon solar cells. More specifically, corrugated silicon solar cells show a unique textured architecture where islands of silicon are interconnected via interdigitated back contacts. Wrinkled PDMS on the silicon islands in addition to flat PDMS anti-reflective coating within the grooves are shown to improve the power output in flexible corrugated solar cells by almost 9%. Wrinkled PDMS is created during the CO2 laser patterning step applied on a bilayer system with a mismatch in the coefficient of thermal expansion, thus causing linear buckling. It should be noted that, in this case, PDMS serves as both a coating for encapsulating and protecting the cells from the external environmental factors such as water, mechanical shock, etc., in addition to a material for reducing light reflection.
  • Mechanical reliability of self-similar serpentine interconnect for fracture-free stretchable electronic devices

    Qaiser, Nadeem; Damdam, Asrar Nabil; Khan, Sherjeel M.; Elatab, Nazek; Hussain, Muhammad Mustafa (Journal of Applied Physics, AIP Publishing, 2021-07-07) [Article]
    Currently, silicon (Si)-based island–interconnect structures are emerging in next-generation stretchable electronic devices such as flexible medical implants, soft robotics, and wearables. Various geometrical designs are being used as interconnects for promising stretchable electronic systems. Among them, self-similar serpentine interconnects (SS-interconnects) are widely used due to their high areal efficiency and stretchability. However, to date, pertinent devices choose random parameters of SS-interconnects since the detailed design guidelines are still elusive. Additionally, no study has revealed how the lateral size or width affects the stretchability during in-plane and out-of-plane stretching. Here, we show how the mechanics could help get the optimized Si-based SS-interconnect without losing its areal efficiency. Our numerical and experimental results show that thin interconnects attain 70%–80% higher stretchability than thicker counterparts. The numerical and experimental results match well. Numerical results indicate the areas prone to break earlier, followed by experimental validation. We devise how induced stress could predict the fracture conditions for any given size and shape of an interconnect. Our results demonstrate that the larger width plays a crucial role in out-of-plane stretching or rotation, i.e., the stress values are 60% higher for the larger width of SS-interconnect during rotation (up to 90°). Our calculations reveal the fracture-free zone for SS-interconnects, showing the figure-of-merit. We demonstrate the detailed guidelines that could help choose the right parameters for fracture-free SS-interconnects for required stretchability, devising the next-generation stretchable and wearable electronic devices.
  • Benchmarking Silicon FinFET With the Carbon Nanotube and 2D-FETs for Advanced Node CMOS Logic Application

    Das, Uttam Kumar; Hussain, Muhammad Mustafa (IEEE Transactions on Electron Devices, IEEE, 2021-06-03) [Article]
    In this article, the performance of silicon FinFET is compared with carbon nanotube (CNT-FET) and 2-D field-effect transistors (2D-FETs) for the upcoming node CMOS logic application. Based on the experimental results, a 17-stage ring oscillator (RO) circuit is implemented using the compact models to analyze the stage-delay and energy-delay performances. A tightly positioned 20- and 10-nm channel-length-based CNT-FET enhances Ion and also increases the leakage currents significantly. Due to poor electrostatic control and increased gate leakage, the CNT-FET and 2D-FET provide lowered Ion and a limited ac performance. Thus, targeting an off-state current, the FinFET delivers more than three times higher drive current, as well as five times better energy-delay performances in comparison to the CNT-FET and 2D-FET. On the other hand, scaled organic FETs are yet far away to compare with FinFET technology. Hence, the silicon-based (3-D) FETs are leading in all the devices (2-D, 1-D, and 0-D) for scaling next-generation CMOS technology.
  • The 2021 flexible and printed electronics roadmap

    Bonnassieux, Yvan; Brabec, Christoph J.; Cao, Yong; Carmichael, Tricia Breen; Chabinyc, Michael L.; Cheng, Kwang Ting; Cho, Gyoujin; Chung, Anjung; Cobb, Corie L.; Distler, Andreas; Egelhaaf, Hans Joachim; Grau, Gerd; Guo, Xiaojun; Haghiashtiani, Ghazaleh; Huang, Tsung Ching; Hussain, Muhammad Mustafa; Iniguez, Benjamin; Lee, Taik Min; Li, Ling; Ma, Yuguang; Ma, Dongge; McAlpine, Michael C.; Ng, Tse Nga; Österbacka, Ronald; Patel, Shrayesh N.; Peng, Junbiao; Peng, Huisheng; Rivnay, Jonathan; Shao, Leilai; Steingart, Daniel; Street, Robert A.; Subramanian, Vivek; Torsi, Luisa; Wu, Yunyun (Flexible and Printed Electronics, IOP Publishing, 2021-05-17) [Article]
    This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.
  • A Robust Wearable Point-of-Care CNT-Based Strain Sensor for Wirelessly Monitoring Throat-Related Illnesses

    Qaiser, Nadeem; Al-Modaf, Fhad; Khan, Sherjeel Munsif; Shaikh, Sohail F.; Elatab, Nazek; Hussain, Muhammad Mustafa (Advanced Functional Materials, Wiley, 2021-05-07) [Article]
    Point-of-care testing (POC) has the ability to detect chronic and infectious diseases early or at the time of occurrence and provide a state-of-the-art personalized healthcare system. Recently, wearable and flexible sensors have been employed to analyze sweat, glucose, blood, and human skin conditions. However, a flexible sensing system that allows for the real-time monitoring of throat-related illnesses, such as salivary parotid gland swelling caused by flu and mumps, is necessary. Here, for the first time, a wearable, highly flexible, and stretchable piezoresistive sensing patch based on carbon nanotubes (CNTs) is reported, which can record muscle expansion or relaxation in real-time, and thus act as a next-generation POC sensor. The patch offers an excellent gauge factor for in-plane stretching and spatial expansion with low hysteresis. The actual extent of muscle expansion is calculated and the gauge factor for applications entailing volumetric deformations is redefined. Additionally, a bluetooth-low-energy system that tracks muscle activity in real-time and transmits the output signals wirelessly to a smartphone app is utilized. Numerical calculations verify that the low stress and strain lead to excellent mechanical reliability and repeatability. Finally, a dummy muscle is inflated using a pneumatic-based actuator to demonstrate the application of the affixed wearable next-generation POC sensor.
  • Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

    Mishra, Rishabh B.; Elatab, Nazek; Hussain, Aftab M.; Hussain, Muhammad Mustafa (Advanced Materials Technologies, Wiley, 2021-03-05) [Article]
    For decades, the revolution in design and fabrication methodology of flexible capacitive pressure sensors using various inorganic/organic materials has significantly enhanced the field of flexible and wearable electronics with a wide range of applications in aerospace, automobiles, marine environment, robotics, healthcare, and consumer/portable electronics. Mathematical modelling, finite element simulations, and unique fabrication strategies are utilized to fabricate diverse shapes of diaphragms, shells, and cantilevers which function in normal, touch, or double touch modes, operation principles inspired from microelectromechanical systems (MEMS) based capacitive pressure sensing techniques. The capacitive pressure sensing technique detects changes in capacitance due to the deformation/deflection of a pressure sensitive mechanical element that alters the separation gap of the capacitor. Due to advancement in state-of-the-art fabrication technologies, the performance and properties of capacitive pressure sensors are enhanced. In this review paper, recent progress in flexible capacitive pressure sensing techniques in terms of design, materials, and fabrication strategies is reported. The mechanics and fabrication steps of paper-based low-cost MEMS/flexible devices are also broadly reported. Lastly, the applications of flexible capacitive pressure sensors, challenges, and future perspectives are discussed.
  • Acceleration Sensors: Sensing Mechanisms, Emerging Fabrication Strategies, Materials, and Applications

    Babatain, Wedyan; Bhattacharjee, Sumana; Hussain, Aftab M.; Hussain, Muhammad Mustafa (ACS Applied Electronic Materials, American Chemical Society (ACS), 2021-01-15) [Article]
    Accelerometers are among the most mature sensor technologies with a broad range of applications in multiple fields and industries. They represent the most widely used microelectromechanical system (MEMS) devices with excellent and reliable performance. MEMS acceleration sensors established dominance mainly in navigation and control applications. In recent years, however, recent technologies and materials have emerged that introduce novel sensing mechanisms, improve performance, enable customization, reduce cost, and reduce fabrication complexity. Herein, the recent advances in accelerometers based on MEMS and recent emerging technologies are reviewed. This work provides a comprehensive review of accelerometers’ sensing mechanisms and the main characteristics and features of each type of sensor, material, and fabrication strategies used to fabricate them. From the aspect of sensor application, this work focuses on reviewing applications that demonstrate the use of accelerometers manufactured using unconventional technologies and materials in prevailing fields such as healthcare monitoring, automotive industry, navigation, building, and structural monitoring. Moreover, challenges and future efforts needed to be addressed in this field are summarized.
  • Paper as a Substrate and an Active Material in Paper Electronics

    Khan, Sherjeel M.; Nassar, Joanna M.; Hussain, Muhammad Mustafa (ACS Applied Electronic Materials, American Chemical Society (ACS), 2020-11-16) [Article]
    Paper is an essential part of our daily life in many different ways. It is made by compressing cellulose fibers sourced from wood into thin sheets. Paper is an inherently flexible material which can transport liquids through its medium by capillary action without the need of external force. The mesh network of cellulose in paper gives it a unique set of mechanical properties. Owing to its exclusive and advantageous properties, paper is being used as an active material and a substrate in electronics. Paper as an active material means that paper is utilized in its intrinsic form without modifications. Activated (or functionalized) paper has been widely exploited in many applications, but in order to take true advantage of all the beneficial properties of paper, it needs to be used in its natural produced form. Notably, paper is employed in humidity sensors, pressure sensors, and MEMS devices in its natural form. Additionally, paper is used as a substrate in additively manufactured and origami-inspired electronic devices. Here, we present an overview of how paper is used to make fully flexible and low-cost devices. Furthermore, the emergence of paper-based point-of-care devices is briefly discussed.
  • Symmetrical orientation of spiral-interconnects for high mechanical stability of stretchable electronics

    Qaiser, Nadeem; Damdam, Asrar Nabil; Khan, Sherjeel Munsif; Hussain, Muhammad Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2020-10-30) [Conference Paper]
    Recently, interconnect based stretchable electronic devices have attained growing interest due to its application for various state-of-the-art technologies. Here, we report an engineered design of spiral interconnects for a series of stretchable networks referred to as the symmetrical series; wherein spirals connect to the island in the symmetry manner. A systematic analysis of Si-based spiral interconnects by numerical modeling, and experiments show that our design provides higher stretchability of 165% in comparison to the conventionally used nonsymmetrical design. The reason for high mechanical reliability is attributed to the favorable unwrapping profile of spiral interconnect due to the nature of forces acting on it during the stretching process. In contrast, for the nonsymmetrical series, the nature of tensile forces produces the rotation, and resultant tilting of spiral arm results in low stretchability of 150%. As a result, nonsymmetrical interconnect fails at earlier stages of stretching. Our study demonstrates the significance of the orientation of spiral interconnects linked to the island to attain the high performance of stretchable electronic devices.
  • Design Criteria for Horseshoe and Spiral-Based Interconnects for Highly Stretchable Electronic Devices

    Qaiser, Nadeem; Damdam, Asrar Nabil; Khan, Sherjeel Munsif; Bunaiyan, Saleh; Hussain, Muhammad Mustafa (Advanced Functional Materials, Wiley, 2020-10-27) [Article]
    Stretchable electronics can be used for numerous advanced applications such as soft and wearable actuators, sensors, bio-implantable devices, and surgical tools because of their ability to conform to curvilinear surfaces, including human skin. The efficacy of these devices depends on the development of stretchable geometries such as interconnection-based configurations and the associated mechanics that helps to achieve optimum configurations. This work presents the essential mechanics of silicon (Si) island-interconnection structures, which include horseshoe and spiral interconnections, without reducing the areal efficiency. In particular, this study demonstrates the range of the geometrical parameters where they have a high stretchability and cyclic life. The numerical results predict the areas that are prone to breaking followed by experimental validation. The figure-of-merit for these configurations is achieved by mapping the fracture-free zones for in-plane and out-of-plane stretching with essential implications in stretchable and wearable system design. Furthermore, this work demonstrates the mechanical response for a range of materials (i.e., copper, gold, aluminum, silver, and graphene) that experience the plastic deformations in contrast to conventionally used Si-based devices that represent the extended usage for advanced stretchable electronic devices. The detailed mechanics of these configurations provides comprehensive guidelines to manufacture wearable and stretchable electronic devices.
  • Mechanically flexible viscosity sensor for real-time monitoring of tubular architectures for industrial applications

    Nour, Maha A.; Khan, Sherjeel M.; Qaiser, Nadeem; Bunaiyan, Saleh A.; Hussain, Muhammad Mustafa (Engineering Reports, Wiley, 2020-10-25) [Article]
    Real-time monitoring of fluid viscosities in tubular systems is essential for industries transporting fluid media. The available real-time viscometers for tubular systems have major drawbacks, such as using invasive methods with large pressure drops due to flow disturbances, destructive installation processes with permanent tube damage, and limited operability with laminar flows. Therefore, developing a viscometer to address the above-mentioned concerns is required for industrial applications. In this study, a new application of a velocity-dependent viscometer using a novel design for real-time measurements with insignificant flow disruption is proposed. It involves a Poly (methyl-methacrylate) microchannel bridge with a microfluidic flowmeter attached to a mechanically flexible Polydimethylsiloxane platform connected to the inner surface of the pipe, which can adapt to different pipe diameters and curvatures. Moreover, the proposed viscometer uses the pipe flow driving force to flow fluids into the microchannel for measurement without requiring a pumping system or any sample withdrawals. The results of the simulation analysis match the experimental results of the sensor performance. The sensor can measure different viscosities in the range of 4-334 mPa s with a resolution higher than 2.7 mPa s. Finally, a stand-alone system is integrated with the sensor for wireless data transmission.
  • Stress concentration analysis and fabrication of silicon (100) based ultra-stretchable structures with parylene coating

    Rehman, Mutee Ur; Babatain, Wedyan; Shaikh, Sohail F.; Conchouso Gonzalez, David; Qaiser, Nadeem; Hussain, Muhammad Mustafa; Rojas, Jhonathan Prieto (Extreme Mechanics Letters, Elsevier BV, 2020-10-19) [Article]
    Research in stretchable electronics is helping to revolutionize the current electronic industry, particularly in wearable and bio-integrated devices. Cost-effectiveness and easy manufacturing are key factors that contribute to shaping the fate of such technologies. In this work, we present a fabrication method for a novel ultra-stretchable, serpentine-arm spiral (SAS) that was built using a low-cost, standard bulk silicon (100) wafer. However, structural defects that often appear during patterning processes, can lead to stress concentration and structural failure at these sites upon stretching. Parylene coating of the structures is proposed to minimize this stress concentration and improve structure's robustness. Finite element analysis (FEA) was performed to demonstrate the concentration of stress at these defective sites with 2 sizes (0.1μm and 1μm) and at different locations along the arms. Results show that SAS structures reach up to ∼80% stress reduction at the defective location compared to straight-arm spirals, while the parylene-coating helps to reduce it up to ∼60% further. On the other hand, fabricated uncoated, SAS structures reached up to ∼600% prescribed strain before fracture, while parylene-coating improves this maximum admissible strain in ∼50%. Additionally, a cyclic tensile test was then performed on the fabricated structures, uncoated and parylene-coated, for over 3000 cycles without fracture. The results observed on coated structures greatly improve the mechanical reliance of such brittle structures, which could be extended to other stretchable configurations.
  • Multi-Dimensional Integration and Packaging of Devices for Internet-of-Things Applications

    Elatab, Nazek; Suwaidan, Reema; Alghamdi, Yara; Alhazzany, Alhanouf; Almansour, Reema; Shaikh, Sohail F.; Khan, Sherjeel M.; Hussain, Muhammad Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2020-10-13) [Conference Paper]
    IoT applications are increasingly becoming widespread with more stringent system requirements. In this work, we demonstrate a nature-inspired integration and packaging technology that achieves self-powered multi-functional systems with optimized performance and small footprint area. The integration technique is based on bifacial usage of the substrate where devices on both sides are interconnected via through-substrate-vias. Multiple substrates are then integrated and folded into a 3D architecture using side-interlocks following a puzzle-like fashion. On the outer sides of the 3D architecture, sensors, RF devices and energy harvesters are integrated while on the inner faces, a solid-state battery in addition to power- management and data-management circuitry are embedded. To package the system, a polymeric encapsulant is used to protect the inner circuitry and enhance the mechanical resilience of the system. Finally, the system is used to send the collected data wirelessly to a phone using an embedded Bluetooth Low Energy unit.
  • Expandable Polymer Assisted Wearable Personalized Medicinal Platform

    Babatain, Wedyan; Gumus, Abdurrahman; Wicaksono, Irmandy; Buttner, Ulrich; Elatab, Nazek; Rehman, Mutee Ur; Qaiser, Nadeem; Conchouso Gonzalez, David; Hussain, Muhammad Mustafa (Advanced Materials Technologies, Wiley, 2020-09-09) [Article]
    Conventional healthcare, thoughts of treatment, and practice of medicine largely rely on the traditional concept of one size fits all. Personalized medicine is an emerging therapeutic approach that aims to develop a therapeutic technique that provides tailor-made therapy based on everyone’s individual needs by delivering the right drug at the right time with the right amount of dosage. Advancement in technologies such as wearable biosensors, point-of-care diagnostics, microfluidics, and artificial intelligence can enable the realization of effective personalized therapy. However, currently, there is a lack of a personalized minimally invasive wearable closed-loop drug delivery system that is continuous, automated, conformal to the skin, and cost-effective. Here, design, fabrication, optimization, and application of a personalized medicinal platform augmented with flexible biosensors, heaters, expandable actuator and processing units powered by a lightweight battery are shown. The platform provides precise drug delivery and preparation with spatiotemporal control over the administered dose as a response to real-time physiological changes of the individual. The system is conformal to the skin, and the drug is transdermally administered through an integrated microneedle. The developed platform is fabricated using rapid, cost-effective techniques that are independent of advanced microfabrication facilities to expand its applications to low-resource environments.
  • Soft Actuators for Soft Robotic Applications: A Review

    Elatab, Nazek; Mishra, Rishabh B.; Al-Modaf, Fhad; Joharji, Lana; Alsharif, Aljohara A.; Alamoudi, Haneen; Diaz, Marlon; Qaiser, Nadeem; Hussain, Muhammad Mustafa (Advanced Intelligent Systems, Wiley, 2020-08-23) [Article]
    Soft robotics technologies are paving the way toward robotic abilities which are vital for a wide range of applications, including manufacturing, manipulation, gripping, human–machine interaction, locomotion, and more. An essential component in a soft robot is the soft actuator which provides the system with a deformable body and allows it to interact with the environment to achieve a desired actuation pattern, such as locomotion. This Review article aims to provide researchers interested in the soft robotics field with a reference guide about the various state-of-the-art soft actuation methodologies that are developed with a wide range of stimuli including light, heat, applied electric and magnetic fields with a focus on their various applications in soft robotics. The underlying principles of the soft actuators are discussed with a focus on the resulting motion complexities, deformations, and multi-functionalities. Finally, various promising applications and examples of the different soft actuators are discussed in addition to their further development potential.
  • Multisensory graphene-skin for harsh-environment applications

    Shaikh, Sohail F.; Hussain, Muhammad Mustafa (Applied Physics Letters, AIP Publishing, 2020-08-17) [Article]
    Monitoring the environment using electronic systems in harsh environments requires materials and processes that can withstand harsh environments. Environmental harshness can come from the surrounding temperature, varying pressure, intense radiation, reactive chemicals, humidity, salinity, or a combination of any of these conditions. Here, we present graphene as a candidate for a multisensory flexible platform in harsh-environment applications. We designed sensors for harsh environments like high temperature (operating range up to 650 C), high salinity, and chemical harsh environments (pH sensing) on a single flexible polyimide sheet. The high-temperature graphene sensor gives a sensitivity of 260% higher than the Pt-based sensor. The temperature sensor acts between metal and a thermistor, thereby providing an opportunity to classify the region depending on temperature (<210 C linear and > 210 C up to 650 C as quadratic). Improved performances are observed for salinity and pH sensing in comparison with existing non-graphene solutions. The simple transfer free fabrication technique of graphene on a flexible platform and laser-induced graphene on a flexible polyimide sheet opens the potential for harsh-environment monitoring and multisensory graphene skin in future applications.
  • Flexible High-Efficiency Corrugated Monocrystalline Silicon Solar Cells for Application in Small Unmanned Aerial Vehicles for Payload Transportation

    Elatab, Nazek; Khan, Sherjeel M.; Hussain, Muhammad Mustafa (Energy Technology, Wiley, 2020-08-17) [Article]
    In recent years, small unmanned aerial vehicles (SUAVs) have proven to be exceptionally useful. However, most of the commercially available drones are electric powered and therefore have a short endurance. Solar powered UAVs have recently received increased attention due to their ability to fly continuously for several days using solar energy. For this purpose, solar cells must show high-efficiency, lightweight and ultra-flexibility in order to be fully compliant to the drone wings/body and avoid degrading its aerodynamic characteristics. Nevertheless, previous demonstrations used rigid/semi-flexible cells. Here, corrugated ultra-flexible silicon solar cells (19% efficiency) with a smaller specific weight (645 g/m2, encapsulated) are considered and used. A theoretical comparison between the performances of the corrugated vs. commercial semi-flexible cells is performed in terms of flight endurance in “AtlantikSolar” UAV. The results show that due to the ultra-lightweight of the corrugated cells and their ability to expand at higher temperatures without bowing, an enhancement in the flight time up to 19% can be achieved compared to the commercial cells which enables heavier payloads (7 lbs) transportation. Finally, the corrugated cells (12.5 cm by 4 cm) are experimentally tested on a small-sized drone under different conditions indoors and a 10% extended flight is reported.
  • Flexible and stretchable inorganic solar cells: Progress, challenges, and opportunities

    Elatab, Nazek; Hussain, Muhammad Mustafa (MRS Energy & Sustainability, Springer Nature, 2020-07-01) [Article]
    This review focuses on state-of-the-art research and development in the areas of flexible and stretchable inorganic solar cells, explains the principles behind the main technologies, highlights their key applications, and discusses future challenges. Flexible and stretchable solar cells have gained a growing attention in the last decade due to their ever-expanding range of applications from foldable electronics and robotics to wearables, transportation, and buildings. In this review, we discuss the different absorber and substrate materials in addition to the techniques that have been developed to achieve conformal and elastic inorganic solar cells which show improved efficiencies and enhanced reliabilities compared with their organic counterparts. The reviewed absorber materials range from thin films, including a-Si, copper indium gallium selenide, cadmium telluride, SiGe/III–V, and inorganic perovskite to low-dimensional and bulk materials. The development techniques are generally based on either the transfer-printing of thin cells onto various flexible substrates (e.g., metal foils, polymers, and thin glass) with or without shape engineering, the direct deposition of thin films on flexible substrates, or the etch-based corrugation technique applied on originally rigid cells. The advantages and disadvantages of each of these approaches are analyzed in terms of achieved efficiency, thermal and mechanical reliability, flexibility/stretchability, and economical sustainability.

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