All-Fabric Triboelectric Nanogenerator (AF-TENG) Smart Face Mask: Remote Long-Rate Breathing Monitoring and Apnea Alarm.

Since the beginning of the COVID-19 pandemic, the use of face masks has become not only mandatory in several countries but also an acceptable approach for combating the pandemic. In the quest for designing an effective and useful face mask, triboelectric nanogenerators (TENGs) have been recently proposed. Novel functionalities are provided with the use of TENGs in face masks due to the induced triboelectrification generated by the exhaled and inhaled breath, allowing their use as an energy sensor. Nonetheless, within the face mask, the presence of nontextile plastics or other common triboelectric (TE) materials can be undesired. Herein, we propose the use of an all-fabric TENG (AF-TENG) with the use of high molecular weight polyethylene (UHMWPE) and cotton fabric as negative and positive triboelectric layers, respectively. With these materials, it is possible to detect the breathing of the patient, which in the case of not detecting a signal over a few minutes can trigger an alarm locally, providing valuable time. Also, in this article, we have sent breathing signals locally and remotely to distances up to 20 km via Wi-Fi and LoRa, the same as warning signals in the case of detecting anomalies. This work reveals the use of TENGs in smart face masks as an important tool to be used in difficult epidemiological periods to the general public, bringing much more comfort and relaxation to patients and elderly in today's society, and based on pristine eco-friendly materials.

Wearable Triboelectric Sensor for Respiration and Coughing Monitoring

The COVID-19 Pandemic has reminded society of the vital importance of breathing monitoring, especially in the adult population. Abnormalities in respiration rate may indicate problems in the respiratory organs caused by possible infections, obstructions, certain lung, heart, or neurological conditions, stress, or anxiety. On the other hand, coughing monitoring (another indicator of coronavirus infection) can benefit from unbiased assessment methods that complement the physician's expertise. This manuscript reports the design and experiment results of a portable, low weight, and easy-to-manufacture Triboelectric Nanogenerator-based (TENG-based) respiratory and coughing sensor. The Triboelectric Sensor's (TS) small size and versatile design allow it to be attached to an elastic band or a hook-and-loop band and placed in different body parts or inside a disposable mask. When placed on the body, the triboelectric effect in the sensor layers, resulting from the vibration and movement of the chest, upper abdomen, or neck, is translated into an electric voltage, which is wirelessly transmitted using Low-power Bluetooth (BLE) communication. The results show the good response of the sensor to slow, fast and deep breaths while sitting and standing. The sensor also detects low, fast, and intense coughing events while sitting, standing, and walking. This demonstrates the potential of this technology scarcely used for breath and cough monitoring in literature.

Triboelectric Response of Electrospun Stratified PVDF and PA Structures.

Utilizing the triboelectric effect of the fibrous structure, a very low cost and straightforward sensor or an energy harvester can be obtained. A device of this kind can be flexible and, moreover, it can exhibit a better output performance than a device based on the piezoelectric effect. This study is concerned with comparing the properties of triboelectric devices prepared from polyvinylidene fluoride (PVDF) fibers, polyamide 6 (PA) fibers, and fibrous structures consisting of a combination of these two materials. Four types of fibrous structures were prepared, and then their potential for use in triboelectric devices was tested. Namely, individual fibrous mats of (i) PVDF and (ii) PA fibers, and their combination-(iii) PVDF and PA fibers intertwined together. Finally, the fourth kind was (iv), a stratified three-layer structure, where the middle layer from PVDF and PA intertwined fibers was covered by PVDF fibrous layer on one side and by PA fibrous layer on the opposite side. Dielectric properties were examined and the triboelectric response was investigated in a simple triboelectric nanogenerator (TENG) of individual or combined (i-iv) fibrous structures. The highest triboelectric output voltage was observed for the stratified three-layer structure (the structure of iv type) consisting of PVDF and PA individual and intertwined fibrous layers. This TENG generated 3.5 V at peak of amplitude at 6 Hz of excitation frequency and was most sensitive at the excitation signal. The second highest triboelectric response was observed for the individual PVDF fibrous mat, generating 2.8 V at peak at the same excitation frequency. The uniqueness of this work lies in the dielectric and triboelectric evaluation of the fibrous structures, where the materials PA and PVDF were electrospun simultaneously with two needles and thus created a fibrous composite. The structures showed a more effective triboelectric response compared to the fibrous structure electrospun by one needle.

Triboelectric Nanogenerator from Used Surgical Face Mask and Waste Mylar Materials Aiding the Circular Economy.

Apart from claiming the lives of more than 3.2 million people, the COVID-19 pandemic is worsening the global plastic pollution every day, mainly with the overflux of single-use polypropylene (PP) face masks. In this scenario, as an innovative solution to mitigate plastic pollution as well as to meet the rising electrical energy demand, we are introducing an all-flexible and facile waste material-based triboelectric nanogenerator (WM-TENG), aiding toward the circular economy. The WM-TENG operating in contact separation mode is fabricated using the PP from a used face mask in combination with recovered Mylar sheets from solid wastes as triboelectric contact layers and a flexible supporting structure. After detailed investigation and trials to study the effect of various disinfection mechanisms of PP materials on the energy output of WM-TENG, UV-C radiation is selected for disinfecting the used masks owing to the retention of electrical energy output. Under a tapping force of 3 N, the WM-TENG having an active area of 6 cm2 delivers an open-circuit voltage of 200 V and a short-circuit current density of 0.29 mA/m2, respectively. The WM-TENG also delivered a maximum power density of 71.16 mW/m2 under 108 Ω load. Additionally, the WM-TENG is demonstrated for powering electronic gadgets such as a calculator, digital thermometer, and LCD clock. This flexible and low-cost nanogenerator without any complex fabrication steps is a sustainable solution for the alarming plastic pollution as well as the rising energy demands.

Design of a self-powered triboelectric face mask.

Usage of a face mask has become mandatory in many countries after the outbreak of SARS-CoV-2, and its usefulness in combating the pandemic is a proven fact. There have been many advancements in the design of a face mask and the present treatise describes a face mask in which a simple triboelectric nanogenerator (TENG) with an electrocution layer may serve the purpose of filtration and deactivation of SARS-CoV-2. The proposed mask is designed with multilayer filters, in which the inner three layers act as a triboelectric (TE) filter and the outer one as an electrocution layer (EL). The viral particles experience a mildshock in EL due to the electric field produced between the electrocution layers by contact electrification. Four pairs of triboelectric series fabrics, i.e. polyvinylchloride (PVC)-nylon, polypropylene (PP)-polyurethane (PU), latex rubber-PU, polyimide (PI)-nylon are studied to establish the efficacy of the mask. The motional force exerted on triboelectric filter materials can produce sufficient electric power to activate EL. The proposed mask can be used by a wide range of people because of its triboelectric self-powering (harvesting mechanical energy from daily activities, e.g. breathing, talking or other facial movements) functionalities to ensure effective filtration efficiency. More importantly, it is expected to be potentially beneficial to slow down the devastating impact of COVID-19.