Design of an Ultrasensitive Flexible Bend Sensor Using a Silver-Doped Oriented Poly(vinylidene fluoride) Nanofiber Web for Respiratory Monitoring

Abstract

We propose a design strategy to fabricate a flexible bend sensor (BS) with ultrasensitivity towards airflow using all PVDF nanofiber web based sensing element and electrode to monitor human respiration. The unique electrospinning (rotational speed of collector of 2000 rpm and tip-to-collector distance of 4 cm) with silver nanoparticles interfacing was introduced to prepare an Ag-doped oriented PVDF nanofiber web with high β-phase content as sensing element (AgOriPVDF, β-phase crystallinity ~ 44.5 %). After that, a portion of the prepared AgOriPVDF was processed into flexible and electrically conductive electrode through electroless silver plating technique (SP-AgOriPVDF). Interestingly, the encapsulated AgOriPVDF BS with SP-AgOriPVDF electrode exhibited superior piezoelectric bending response (open-circuit peak-to-peak output voltage, Vp-p ≈ 4.6 V) to injected airflow, which is more than 200 times higher than that of the unpackaged randomly aligned PVDF nanofiber web BS with conductive tape electrode (Vp-p ≈ 0.02 V). In addition, the factors influencing the 2 bend sensitivity of BS such as β-phase content, nanofiber orientation, flexibility of electrode and so forth were thoroughly analyzed and then discussed. We also demonstrated that the AgOriPVDF BS has sufficient capability to detect and identify various respiratory signal, presenting a great potential for wearable applications, e.g. smart respiratory protective equipment.

Respiration‐driven triboelectric nanogenerators for biomedical applications

“…Other technologies such as PENG [110][111][112][113][114] and electromagnetic generator (EMG) [115][116][117][118][119] have the capability of harvesting respiration energy and realize self-powered biomedical system as well. However, the TENGs still stands out with unique merits.…”

Composites, Fabrication and Application of Polyvinylidene Fluoride for Flexible Electromechanical Devices: A Review

“…PVDF and graphene-silver (GAg) nanocomposites have plasma-coupled piezoelectric properties, and the piezoelectric energy conversion efficiency reaches 15% [105]. Using the unique interface structure of silver nanoparticles, silver-doped oriented PVDF nanofibers with a high content of β phase were prepared by electrospinning [106], and the crystallinity of the β phase was 44.5%. Silver nanoparticles in graphene dispersion form n-type doping on graphene owing to electrostatic effects [107][108][109][110][111].…”

“…Gong et al [134] combined the PVDF nanofiber membrane by electrospinning with PDMS-Ag NWS and PET/ITO electrodes to fabricate sensors. Lu et al [106] made a flexible bend sensor to monitor human respiration by electrospinning PVDF and a silver mixed solution (Figure 8b).…”

“…(a) Schematic diagram of the Electrospinning technique; (b) Flexible bend sensor to monitor human respiration[106]; (c) Optical photo and SEM of (BTO)/P(VDF-TrFE) composite nanofibers[97];…”

Flourishing energy harvesters for future body sensor network: from single to multiple energy sources

“…A large number of researches have been performed toward novel wearable PENGs in the past decade bearing the propose of transferring human motions generally with a wide range and low frequency to electricity with a long lifetime and certain comfortability (Pu et al, 2018;Shi et al, 2020c;Wu et al, 2016). Typical improvement directions of PENGs include the capability to withstand large deformation and strain (Chou et al, 2018;Jeong et al, 2015), stability to endure a large number of operation cycles (Cheng et al, 2020;Lu et al, 2020), structure simplicity, lightweight to ensure portability and wearing comfortability (Kim et al, 2020;Wang et al, 2018c), sensitivity for minor motions like respiration (Jin et al, 2020a), and also high output performance (Jeong et al, 2018;Rovisco et al, 2020).…”