Interlocking Matrix and Filler for Enhanced Individualization and Reinforcement in Polymer-Single-Walled Carbon Nanotube Composites

Poor individualization and interfacial adhesion prevent single-walled carbon nanotube (SWNT)-polymer composites from reaching outstanding mechanical properties. With much larger diameters, but common structural features (high aspect ratio and absence of functional groups for covalent or supramolecular attachment with the polymer), carbon fibers face similar problems, which are addressed by covering the fibers with a thin layer of polymer. This sizing strategy has allowed carbon fibers to become the filler of choice for the highest performing materials. Inspired by this, here we investigate the use of the mechanical bond to wrap SWNTs with a layer of polymeric material to produce SWNTs mechanically interlocked with a layer of polymer. We first validate the formation of mechanically interlocked nanotubes (MINTs) using mixtures of SWNTs of relatively large average diameter (1.6 ± 0.4 nm), which are commercially available at reasonable prices and therefore could be technologically relevant as polymer fillers. We then design and synthesize by ring-opening metathesis polymerization (ROMP) a polymer decorated with multiple U-shaped molecules, which are later ring-closed around the SWNTs using metathesis. The obtained hybrids contain a high degree of individualized SWNTs and exhibit significantly increased mechanical properties when compared to the matrix polymer. We envision that this strategy could be employed to produce SWNTs interlocked with polymer layers with various designs for polymer reinforcement.

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.