Flexible strain sensor with high sensitivity, fast response, and good sensing range for wearable applications.

Flexible strain sensors are emerging rapidly and overcoming the drawbacks of traditional strain sensors. However, many flexible sensors failed to balance the sensitivity, response time, and the desired sensing range. This work proposes a novel and cost-effective strain sensor which simultaneously achieved high sensitivity, fast response, and a good sensing range. It illustrates a prototype strain sensor realized with a nanocomposite constituting reduced graphene oxide and palladium as the primary sensing elements. These sensors were fabricated with manual screen-printing technology. The sensor exhibited an outstanding performance for the different strains ranging from 0.1% to 45%. As a result, a substantially high gauge factor around 1523 at a strain of as high as 45% and a rapid response time of 47 ms was obtained. This work demonstrated potential applications like real-time monitoring of pulse and respiration, and other physical movement detection, which become crucial parameters to be measured continuously during the COVID-19 pandemic.

Reduced Graphene Oxide Tattoo as Wearable Proximity Sensor

The human body is punctuated with wide array of sensory systems that provide a high evolutionary advantage by facilitating formation of a detailed picture of the immediate surroundings. The sensors range across a wide spectrum, acquiring input from noncontact audiovisual means to contact-based input via touch and taste. The ambit of sensing can be extended further by imparting the body with increased noncontact sensing capability through the phenomenon of electrostatics. Here, a graphene-based tattoo sensor is presented for proximity sensing, employing the principle of electrostatic gating. The sensor shows a remarkable change in resistance upon exposure to objects surrounded with static charge on them. Compared to prior work in this field, the sensor demonstrates the highest recorded proximity detection range of 20 cm. It is ultrathin, highly skin conformal, and comes with a facile transfer process such that it can be tattooed on the human skin, unlike other graphene-based proximity sensors reported before. Present work details the operation of wearable proximity sensor while exploring the effect of mounting body on the working mechanism. A possible role of the sensor as an alerting system against unwarranted contact with objects in public places especially during the current COVID-19 pandemic is also explored. © 2021 Wiley-VCH GmbH