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.

Abstract

Free-chlorine concentration monitoring is of importance in public and industrial water supplies. Current colorimetric methods, which include test strips, spectrophotometric kits, etc. either lack precision or are expensive and labor intensive. In this study, we present a fully automated, cost-effective method of measurement of free chlorine concentration in real -time. The setup includes an automatic powder dispenser, an automatic liquid dispenser, a sample chamber, and an LED-light-dependent resistor sensor pair. The liquid sample is mixed with a coloring reagent and its color is measured using the sensor pair. Different regression algorithms were trained on the sensor data and tuned to predict the corresponding free-chlorine concentration with maximum accuracy. The system eliminates the need for color matching, reduces the time taken per test, and can be used to predict concentrations of multiple analytes, including ammonia-nitrogen, dissolved oxygen, etc., by adding corresponding colorimetry agents. This allows for a fully automated, real-time water testing system.

Abstract

Analysis of foot pressure, also known as plantar pressure analysis, plays a pivotal role in biomedical assessments related to posture and gait analysis. Extensive research has been conducted on leveraging this technique for clinical purposes, leading to the development of flexible pressure sensors. In this letter, we present the use of in-shoe flexible pressure sensor array for determining the nature of the walking surface. The sensor system is fabricated using eight low-cost and robust, in-shoe pressure sensors that leverage the piezoresistivity of velostat. The sensor array was characterized for four different surface types. Random Forest (RF) algorithm was used to classify the surfaces with 86% accuracy. Based on this analysis, we propose a novel method for analyzing various surfaces based on their attributes such as firmness, rigidity, and penetrability.

Abstract

The rapid proliferation of Internet of Things (IoT) devices and applications has resulted in an increasing demand for Low Power and Wide Area Network (LPWAN) solutions. The adoption of IoT networks still faces several challenges, despite the rapid advancement of low-power communication technology. Homogenizing this sector requires allowing interoperability between many technologies, which is now one of the largest obstacles. In this article, we present the design and implementation of the hybrid LPWAN architecture that can accomplish wide-area communication coverage and low-power consumption for IoT applications by leveraging two LPWAN technologies, Wireless Smart Ubiquitous Network (Wi-SUN) and Long Range (LoRa). In particular, LoRa is used for long-range communication, and Wi-SUN for a low-latency mesh network. Additionally, we implemented smart street light controlling system as a real-world deployment at the university campus to showcase the efficiency of the hybrid network. Our results demonstrate that the hybrid LPWAN architecture provides a better coverage and capacity while consuming less power than that of the LoRa or Wi-SUN network. The results of this study demonstrate the effectiveness of the proposed hybrid LPWAN architecture as a viable solution for next-generation IoT applications.

Abstract

Affordable healthcare, particularly for elderly persons, is an important goal with aging of the world population. Cloud-connected smart sensor systems are an important part of the healthcare ecosystem. In this letter, we present an affordable large area flexible pressure sensor array using a piezoresistive thin film. The dimensions of the sensor are 180 cm × 90 cm, according to the dimensions of a standard single bed mattress. The sensor array consists of eight vertical sensor strips with a high aspect ratio of 120, highest reported so far for a flexible piezoresistive sensor. The measured output of the sensors showed a high signal-to-noise ratio, with loaded and unloaded sensor resistances of 11 pm 3 Omega and 219.2 pm 0.5 kOmega, respectively. The fabrication process has been designed to be conducive to roll-to-roll manufacturing processes to increase scalability and reduce cost. With a sampling frequency of 10 Hz, the sensor array provides real-time information about user position and possible fall events.