We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

Wearable biosensors have received tremendous attention over the past decade owing to their great potential in predictive analytics and treatment toward personalized medicine. Flexible electronics could serve as an ideal platform for personalized wearable devices because of their unique properties such as light weight, low cost, high flexibility and great conformability. Unlike most reported flexible sensors that mainly track physical activities and vital signs, the new generation of wearable and flexible chemical sensors enables real-time, continuous and fast detection of accessible biomarkers from the human body, and allows for the collection of large-scale information about the individual's dynamic health status at the molecular level. In this article, we review and highlight recent advances in wearable and flexible sensors toward continuous and non-invasive molecular analysis in sweat, tears, saliva, interstitial fluid, blood, wound exudate as well as exhaled breath. The flexible platforms, sensing mechanisms, and device and system configurations employed for continuous monitoring are summarized. We also discuss the key challenges and opportunities of the wearable and flexible chemical sensors that lie ahead.

Wearable and flexible electronics for continuous molecular monitoring.

We present Chronos, a system that enables a single WiFi access point to localize clients to within tens of centimeters. Such a system can bring indoor positioning to homes and small businesses which typically have a single access point.

The key enabler underlying Chronos is a novel algorithm that can compute sub-nanosecond time-of-flight using commodity WiFi cards. By multiplying the time-of-flight with the speed of light, a MIMO access point computes the distance between each of its antennas and the client, hence localizing it. Our implementation on commodity WiFi cards demonstrates that Chronos's accuracy is comparable to state-of-the-art localization systems, which use four or five access points.

/pdf/decimeter-level-localization-with-a-single-wifi-access-point-590e4hkp3l.pdf

Decimeter-level localization with a single WiFi access point

Disposable sensors are low-cost and easy-to-use sensing devices intended for short-term or rapid single-point measurements. The growing demand for fast, accessible, and reliable information in a vastly connected world makes disposable sensors increasingly important. The areas of application for such devices are numerous, ranging from pharmaceutical, agricultural, environmental, forensic, and food sciences to wearables and clinical diagnostics, especially in resource-limited settings. The capabilities of disposable sensors can extend beyond measuring traditional physical quantities (for example, temperature or pressure); they can provide critical chemical and biological information (chemo- and biosensors) that can be digitized and made available to users and centralized/decentralized facilities for data storage, remotely. These features could pave the way for new classes of low-cost systems for health, food, and environmental monitoring that can democratize sensing across the globe. Here, a brief insight into the materials and basics of sensors (methods of transduction, molecular recognition, and amplification) is provided followed by a comprehensive and critical overview of the disposable sensors currently used for medical diagnostics, food, and environmental analysis. Finally, views on how the field of disposable sensing devices will continue its evolution are discussed, including the future trends, challenges, and opportunities.

/pdf/disposable-sensors-in-diagnostics-food-and-environmental-579hawpmue.pdf

Disposable Sensors in Diagnostics, Food, and Environmental Monitoring.

This paper presents an overview of the work done on graphene in recent years. It explains the preparation techniques, the properties of graphene related to its physio-chemical structure and some key applications. Graphene, due to its outstanding electrical, mechanical and thermal properties, has been one of the most popular choices to develop the electrodes of a sensor. It has been used in different forms including nanoparticle and oxide forms. Along with the preparation and properties of graphene, the categorization of the applications has been done based on the type of sensors. Comparisons between different research studies for each type have been made to highlight their performances. The challenges faced by the current graphene-based sensors along with some of the probable solutions and their future opportunities are also briefly explained in this paper.

Graphene and its sensor-based applications: A review

This paper provides a review on some of the significant research work done on wearable flexible sensors (WFSs). Sensors fabricated with the flexible materials have been attached to a person along with the embedded system to monitor a parameter and transfer the significant data to the monitoring unit for the further analyses. The use of wearable sensors has played a quite important role to monitor the physiological parameters of a person to minimize any malfunctioning happening in the body. This paper categorizes the work according to the materials used for designing the system, the network protocols, and different types of activities that were being monitored. The challenges faced by the current sensing systems and future opportunities for the WFSs regarding its market values are also briefly explained in this paper.

/pdf/wearable-flexible-sensors-a-review-4rnpuj98sl.pdf

Wearable Flexible Sensors: A Review

The paper presents a substantial review of the work done on the design and development of different types of gas sensors using Carbon Nanotubes. The fundamental techniques of preparation of Carbon Nanotubes have also been reported here. The variety of sensors, their detection processes of a range of gases including NO2, H2S, C2H5OH, and others have been described here. Single-Walled and Multi-Walled Carbon Nanotubes in their pristine and amalgamated forms has been used and to develop a range of sensing devices. It also presents a comparative study on each gas giving the fundamental parameters like the limit of detection, the range of concentration and response time to differentiate their capability regarding the materials used to fabrication them to detect the gases. Finally, the challenges related to the currently available Carbon Nanotubes-based gas sensors, their associated remedial actions and some of the possible opportunities for future work are elucidated in the paper.

Carbon nanotubes and its gas-sensing applications: A review

This paper showcases a substantial review on some of the significant work done on 3D printing of sensors for biomedical applications. The importance of 3D printing techniques has bloomed in the sensing world due to their essential advantages of quick fabrication, easy accessibility, processing of varied materials and sustainability. Along with the introduction of the necessity and influence of 3D printing techniques for the fabrication of sensors for different healthcare applications, the paper explains the individual methodologies used to develop sensing prototypes. Six different 3D printing techniques have been explained in the manuscript, followed by drawing a comparison between them in terms of their advantages, disadvantages, materials being processed, resolution, repeatability, accuracy and applications. Finally, a conclusion of the paper is provided with some of the challenges of the current 3D printing techniques about the developed sensing prototypes, their corresponding remedial solutions and a market survey determining the expenditure on 3D printing for biomedical sensing prototypes.

https://www.mdpi.com/1424-8220/19/7/1706/pdf

3D Printed Sensors for Biomedical Applications: A Review.

The paper presents the design, development, and fabrication of a flexible and wearable sensor based on carbon nanotube nanocomposite for monitoring specific physiological parameters. Polydimethylsiloxane (PDMS) was used as the substrate with a thin layer of a nanocomposite comprising functionalized multi-walled carbon nanotubes (MWCNTs) and PDMS as electrodes. The sensor patch functionalized on strain-sensitive capacitive sensing from interdigitated electrodes which were patterned with a laser on the nanocomposite layer. The thickness of the electrode layer was optimized regarding strain and conductivity. The sensor patch was connected to a monitoring device from one end and attached to the body on the other for examining purposes. Experimental results show the capability of the sensor patch used to detect respiration and limb movements. This work is a stepping stone of the sensing system to be developed for multiple physiological parameters.

/pdf/flexible-carbon-nanotube-nanocomposite-sensor-for-multiple-231923bwis.pdf

Anindya Nag

Papers

Graphene and its sensor-based applications: A review

Wearable Flexible Sensors: A Review

Carbon nanotubes and its gas-sensing applications: A review

3D Printed Sensors for Biomedical Applications: A Review.

Flexible carbon nanotube nanocomposite sensor for multiple physiological parameter monitoring