An ultrafine spider-like carbon nanonet for high performance air filters, health monitoring sensors, and green energy generators

We report an innovative approach for fabricating a gradient dual nanonet (NF@CNT) consisting of poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers with a diameter of 0.68 +/- 0.15 mu m and ultrafine spider-like nanonets with a diameter of 23.30 +/- 6.67 nm. The spider-like nanonet formation mechanism is probably due to the hydrogen bonding interactions between single wall carbon nanotubes (SWCNTs) and PVA-co-PE nanofibers or between SWCNTs. The NF@CNT-2 air filter exhibits a relatively high water vapor transmission rate (WVTR) of 4732.63 +/- 626.28 g (m2 d)-1, a high filtration efficiency of 95.62 +/- 0.52%, and a low pressure drop of 105.33 +/- 1.53 Pa. Additionally, it can be assembled as a resistance sensor to detect human motion, such as finger bending and releasing, as well as physiological signals including wrist pulse rate (66 times per min), vocal recognition, and respiration rate (normal 16 times per min, after exercise 55-56 times per min). Furthermore, it can also be reused as a transpiration driven electrokinetic power generator (TEPG), with a size of 66 mm x 10 mm providing a maximum open circuit voltage (Voc) of 0.57 V by dripping 85 mu L of 0.1 M ferric chloride solution, and six units serially can power a red LED and a calculator, respectively. The NF@CNT air filters are composed of PVA-co-PE nanofibers and ultrafine spider-like carbon nanonets, and can be applied in comfortable face masks, human motion and physiological signal monitoring sensors, and TEPGs for green power generation.