Abstract

The Log-Distance Path Loss (LDPL) model is a commonly used methodology to measure signal attenuation in Long Range Wide Area Networks (LoRaWAN), a wireless protocol primarily used for Internet of Things (IoT) applications. In this paper, we establish the limitations of this model even in near-ideal, line-of-sight (LoS) conditions, owing to significant deviations in empirical constants despite accounting for fading effects. The Path Loss Exponent (PLE) and the variance of shadow fading were calculated using Received Signal Strength Index (RSSI) measurements. They were obtained by sweeping the transmitter along radial and tangential directions with respect to a fixed receiver. At each transmitter position, multiple RSSI values were averaged to eliminate temporal fading. Both the transmitter and the receiver were secured at 0.5 m off the ground. The measurements were taken in an empty ground with transmitterreceiver LoS and minimal reflections, thus ensuring near-ideal experimental conditions. The PLE varied from 1.84 to 3.90 and the shadow fading varied from 0.5 dB to 5.8 dB, thus challenging the accuracy of RSSI applications, such as localization, that frequently use this model.

Abstract

The rapid adoption of electric vehicles (EVs) has accelerated the need for scalable, cost-effective charging infrastructure, particularly in urban environments. This paper presents an integrated approach to EV charging, combining Wireless Smart Ubiquitous Network (Wi-SUN) technology with Bluetooth Low Energy (BLE) for enhanced connectivity and cost-effective deployment. The proposed system addresses the limitations of traditional cellular and Wi-Fi networks by leveraging Wi-SUN's long-range capabilities for connecting to the cloud to obtain and update user information. The system uses BLE's energy efficiency for last-mile connectivity and user authentication. Deployed within an operational Wi-SUN network at the International Institute of Information Technology (IIIT) Hyderabad, the system demonstrates reliable performance, including low-latency user authentication and scalable integration with smart city infrastructure. The data pertaining to each charging session is semantically stored in a middleware platform based on the oneM2M standard. Specific data about a user or a charging station can be queried from this platform and reported through a dashboard. This study underscores the potential of BLE as a robust last-mile solution for smart city applications, advancing sustainable and interconnected urban infrastructure.

Abstract

There are several use-cases where the hardness of a surface can be an important parameter - construction, infrastructure, sports fields, and so on. At present, there are no low-cost, thin-film, and wearable-based solutions for this problem. This study presents the development and evaluation of an insole-based sensing system for detecting and characterizing variations in surface conditions. The system integrates velostat, a piezoresistive material, into an insole to accurately capture plantar pressure variations as users traverse diverse terrains. The pressure data are subsequently processed to generate a detailed map differentiating various surface types. Experimental validation demonstrates that the system is capable of successfully mapping two distinct surfaces with an accuracy of 88.8 %. Multiple machine learning algorithms were analyzed to optimize the system performance and validate its efficacy. This approach has significant implications for the maintenance of a sports field, the optimization of athlete performance, and the prevention of injury.

Abstract

Mimicking the sensory capabilities of human skin has long been a challenge in the development of intelligent electronic systems. This study introduces a high-performance paper-based electronic skin (e-skin) capable of detecting pressure and temperature simultaneously from the same pixel. The eskin fabricated herein is utilizes paper as a substrate along with velostat thin film and NTC thermistors that enable real-time monitoring of mechanical and thermal stimuli. Both pressure and temperature sensing mechanisms rely on changes in resistance under applied stimulus. The readout is done using an integrated crossbar architecture for both the sensors simultaneously. The lightweight and flexible nature of the paper-based platform makes it suitable for applications in soft robotics and wearable health monitoring. The experimental results demonstrate high sensitivity, stability and rapid response to external stimuli. This work paves the way for the development of multifunctional, large area, low-cost, and sustainable e-skin solutions for nextgeneration flexible electronics and robotics applications.

Abstract

Flexible capacitive pressure sensors have simple sensing structure, zero-temperature drift, linear response, and high sensitivity, leading to applications in human healthcare including soft and surgical robotics, human machine interaction (HMI) and wearable devices. In this paper, we present a highly compressible multilayer flexible capacitive pressure sensor, based on air/vapour bubble-induced PDMS foam thin-film as dielectric and polypyrrole coated cotton textile as electrodes. An in-situ chemical oxidative polymerisation method was used to synthesize a conducting, large area polypyrrole coated cotton textile. We used this as parallel electrodes on the top and bottom of the bubble-induced PDMS foam. The bubble-induced PDMS film was made by casting of PDMS, mix with specific amounts of ethanol. The top and bottom textile electrodes were then attached to it with the help of silicone adhesive. We observed low hysteresis, high repeatability, and good step response in our sensor characterisation. Bubble characterisation was also performed including surface profilometer and scanning electron microscopy (SEM). We showcase two applications of our sensor including mouse click and grasping of a cup. The sensor can be fabricated in different shapes and sizes for various applications of free-form electronics such as soft and surgical robotics, wearable, biomedical, human-machine interaction, and so on.

Abstract

The scalability and reliability of any large scale IoT network depends on a multitude of things, the primary one of that, being the communication protocol underlying the system. Wi-Sun is a novel protocol that offers a low power, long range and cost effective solution. It is a mesh protocol such that any node can be configured to be a transceiver. The mesh forms a destination oriented directed acyclic graph (DODAG) with one node configured to be the border router that connects to the internet, enabling cloud access for the entire mesh. However, long connection time and healing time of the DODAG are some of its drawbacks. In this paper, we present experiments on a real-world deployment of a Wi-Sun network where we study patterns in the time required for each additional node to be added in the Wi-Sun network, and investigate the time required to reform a new DODAG when a node with a certain hop count is detached. This deployment can also serve as a testbed for future such evaluations.

Abstract

Free-form electronics are one of the major chal-
lenges being tackled in the present era. Along with the substrate and components, the conductive materials used in these also have to endure the applied strain, hence, thin film based conductors are being studied extensively. In this work, we report bending behavior of conductive CNT-PDMS thin film channels. Transmission Line Method (TLM) based resistance calculations have
been done to precisely analyze the CNT thin film sheet resistance and the contact resistance. This exercise allows us to look at the effectiveness of CNT channels as a conductive path and also helps us understand their behavior over concentration, path length and strain caused due to bending. We report sheet resistance values of 254 Ω/□ and 1.41 Ω/□ for thin films of two different CNT concentrations. The contact resistances for these films were 230Ω and 315 Ω respectively. We observed that bending induced strain caused the resistance values to increase from 3.95 kΩ for
flat to 13.1 kΩ for bending radius of 1.2 cm.

Abstract

Recent literature in soft robotics has been focused
on bio-mimetic technologies, i.e., trying to replicate naturally-occurring structures, such as artificial muscles. Flapping structures have been reported, wherein a soft wing is paired with a solid actuator or vice-versa, but a fully soft actuator and wing setup has only recently been developed. In this work, we present the fabrication and characterization of the electrical response of a fully soft DEA-based flapping wing actuator. The actuator
was fabricated using a urethane acrylate polymer elastomer with carbon nanotube (CNT) based electrodes. The 40 mm × 20 mm rectangular actuator was powered through two electrodes. It was subjected to static DC voltages in the range of 1 kV to 2 kV and
the current and energy drawn by the actuator were observed. We report the average settling current varying from 7 μA to 43 μA and energy draw varying from 220 mJ to 715 mJ. Further tests on a similarly fabricated actuator revealed the possibility of Time Dependent Dielectric breakdown (TDDB) encountered
at 2kV after nearly 120 minutes.

Abstract

This paper presents the architecture of a two-wheeler mobile sensing platform aimed at collecting compre-hensive two-wheeler riding data. Two-wheelers, prevalent in many countries for their agility and efficiency lack extensive study in autonomous vehicle research. Recognizing this gap, our work introduces a scalable and modular platform equipped with multiple sensors and high-performance embedded systems. The platform captures essential data points such as GPS, acceleration, gyroscope, speed, and 360-degree image and depth data, crucial for developing deep learning models for autonomous navigation and accident prevention. We detail the hardware architecture, consisting of an Nvidia Jetson TX2 NX platform, Raspberry Pi 4 Model B, and various sensors, all tailored to operate efficiently on a two-wheeler. The software methodology is designed to synchronize and process the data effectively, hence allowing us to generate accurate and thorough datasets. Our results demonstrate the platform's potential in improving two-wheeler safety and contributing to the advancement of autonomous vehicle technologies.

Abstract

Flexible electronics are integral in numerous domains such as wearables, healthcare, physiological monitoring, human-machine interface, and environmental sensing, owing to their inherent flexibility, stretchability, lightweight construction, and low profile. These systems seamlessly conform to curvilinear surfaces, including skin, organs, plants, robots, and marine species, facilitating optimal contact. This capability enables flexible electronic systems to enhance or even supplant the utilization of cumbersome instrumentation across a broad range of monitoring and actuation tasks. Consequently, significant progress has been realized in the development of flexible electronic systems. This study begins by examining the key components of standalone flexible electronic systems-sensors, front-end circuitry, data management, power management and actuators. The next section explores different integration strategies for flexible electronic systems as well as their recent advancements. Flexible hybrid electronics, which is currently the most widely used strategy, is first reviewed to assess their characteristics and applications. Subsequently, transformational electronics, which achieves compact and high-density system integration by leveraging heterogeneous integration of bare-die components, is highlighted as the next era of flexible electronic systems. Finally, the study concludes by suggesting future research directions and outlining critical considerations and challenges for developing and miniaturizing fully integrated standalone flexible electronic systems.