Highly Sensitive and Stretchable MXene/CNTs/TPU Composite Strain Sensor with Bilayer Conductive Structure for Human Motion Detection

Abstract

The universal application of wearable strain sensors in various situations for human-activity monitoring is considerably limited by the contradiction between high sensitivity and broad working range. There still remains a huge challenge to design sensors featuring simultaneous broad working range and high sensitivity. Herein, a typical bilayer-conductive structure Ti3C2T x MXene/carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU) composite film was developed by a simple and scalable vacuum filtration process utilizing a porous electrospun thermoplastic polyurethane (TPU) mat as a skeleton. The MXene/CNTs/TPU strain sensor is composed of two parts: a brittle densely stacked MXene upper lamella and a flexible MXene/CNT-decorated fibrous network lower layer. Benefiting from the synergetic effect of the two parts along with hydrogen-bonding interactions between the porous TPU fiber mat and MXene sheets, the MXene/CNTs/TPU strain sensor possesses both a broad working range (up to 330%) and high sensitivity (maximum gauge factor of 2911) as well as superb long-term durability (2600 cycles under the strain of 50%). Finally, the sensor can be successfully employed for human movement monitoring, from tiny facial expressions, respiration, and pulse beat to large-scale finger and elbow bending, demonstrating a promising and attractive application for wearable devices and human–machine interaction.

Estimation of Respiratory Frequency in Women and Men by Kubios HRV Software Using the Polar H10 or Movesense Medical ECG Sensor during an Exercise Ramp

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Development and Optimization of Silicon−Dioxide−Coated Capacitive Electrode for Ambulatory ECG Measurement System

“…Figure 3 c shows an electrode having a 0.5 cm diameter and total thickness of the electrodes was about 240 μm. The capacitive−coupled electrodes were fabricated with thin and flexible structure to guarantee good mechanical contact between the skin and the electrode and this characteristic reduces baseline wandering and motion artifacts [ 29 , 30 ]. In order to measure the surface resistance of the capacitive−coupled electrode, we used a four−point probe (Keithley, 2400 source meter) as shown in Figure 3 d. The surface resistance was repeatedly measured by selecting five random positions according to the size of the electrodes.…”

Janus and Heteromodulus Elastomeric Fiber Mats Feature Regulable Stress Redistribution for Boosted Strain Sensing Performance

“…In general, stretchable strain sensors with high sensitivity for a wide strain range are greatly favored for practical sensing applications if the signal-to-noise ratio is considered for easy signal recognition. To date, many strategies, such as the use of hybrid nanofillers, , segregated network structures, , bilayer structures, ,,− construction of microcracks by prestrains, , or surface micro/nanoscale structures by micro/nano-fabrications, ,, have already been reported to achieve high sensitivity in resistive strain sensors. The values of relative resistance change (Δ R / R 0 ) ranging from 10 2 to 10 6 for a 50% strain have been widely reported in the literature, − indicating a large achievement of strain sensitivity that is contributed by the methods for improving strain sensitivity.…”