Silver Nanoparticle-Decorated Multiwalled Carbon Nanotube Ink for Advanced Wearable Devices

Abstract

Silver nanoparticles of average size 12–13 nm were successfully decorated on the surface of multiwalled carbon nanotubes (MWCNTs) through a scalable wet chemical method without altering the structure of the MWCNTs. Employing this Ag@MWCNT, a multifunctional room-temperature curable conductive ink was developed, with PEDOT:PSS as the conductive binder. Screen printing of the ink could yield conductive planar traces with a 9.5 μm thickness and a conductivity of 28.99 S/cm, minimal surface roughness, and good adhesion on Mylar and Kapton. The versatility of the ink for developing functional elements for printed electronics was demonstrated by fabricating prototypes of a wearable strain sensor, a smart glove, a wearable heater, and a wearable breath sensor. The printed strain sensor exhibited a massive sensing range for wearable applications, including an impressive 1332% normalized resistance change under a maximum stretchability of 23% with superior cyclic stability up to 10 000 cycles. The sensor also exhibited an impeccable gauge factor of 142 for a 5% strain (59 for 23%). Furthermore, the sensor was integrated into a smart glove that could flawlessly replicate a human finger’s gestures with a minimal response time of 225–370 ms. Piezoresistive vibration sensors were also fabricated by printing the ink on Mylar, which was employed to fabricate a smart mask and a smart wearable patch to monitor variations in human respiratory and pulmonary cycles. Finally, an energy-efficient flexible heater was fabricated using the developed ink. The heater could generate a uniform temperature distribution of 130 °C at the expense of only 393 mW/cm2 and require a minimum response time of 20 s. Thus, the unique formulation of Ag@MWCNT ink proved suitable for versatile devices for future wearable applications.

Perforated PVP encapsulated AgNWs for high mass loading in silver nanowire inks for printed RFID integrated wearable smart bands

“…The printed traces exhibited linear current–voltage characteristics, suggesting the formation of ideal ohmic conductive traces realized via printing. 39 The printed traces maintained this linear current–voltage dependence even after the 10 000 th bending cycle with a nearly slight increase in slope, as observed in Fig. 4(c).…”

Surface Embedded Metal Nanowire–Liquid Metal–Elastomer Hybrid Composites for Stretchable Electronics

“…Typically, these single-filler composites require high filler loading to reach percolation, which compromises stretchability of the elastomer-based composites. They also undergo a significant increase in the electrical resistance upon mechanical deformation due to degradation of the percolating network under strain, i.e., separation of the conductive fillers. − To counter these issues, conductive composites with more than one type of conductive fillers have been developed, termed as hybrid-filler (or hybrid) composites …”