Additively Manufactured Flexible Electronics with Ultrabroad Range and High Sensitivity for Multiple Physiological Signals’ Detection

Abstract

Flexible electronics can be seamlessly attached to human skin and used for various purposes, such as pulse monitoring, pressure measurement, tensile sensing, and motion detection. Despite their broad applications, most flexible electronics do not possess both high sensitivity and wide detection range simultaneously; their sensitivity drops rapidly when they are subjected to even just medium pressure. In this study, ultrabroad-range, high-sensitivity flexible electronics are fabricated through additive manufacturing to address this issue. The key to possess high sensitivity and a wide detection range simultaneously is to fabricate flexible electronics with large depth-width ratio circuit channels using the additive manufacturing inner-rinsing template method. These electronics exhibit an unprecedented high sensitivity of 320 kPa−1 over the whole detection range, which ranges from 0.3 to 30,000 Pa (five orders of magnitude). Their minimum detectable weight is 0.02 g (the weight of a fly), which is comparable with human skin. They can stretch to over 500% strain without breaking and show no tensile fatigue after 1000 repetitions of stretching to 100% strain. A highly sensitive and flexible electronic epidermal pulse monitor is fabricated to detect multiple physiological signals, such as pulse signal, breathing rhythm, and real-time beat-to-beat cuffless blood pressure. All of these signals can be obtained simultaneously for detailed health detection and monitoring. The fabrication method does not involve complex expensive equipment or complicated operational processes, so it is especially suitable for the fabrication of large-area, complex flexible electronics. We believe this approach will pave the way for the application of flexible electronics in biomedical detection and health monitoring.

Rational Design of Conductive Pathways in Flexible Tactile Sensors via Indirect 3D-Printing of Liquid Metal for High-Precision Monitoring and Recognition

“…First, the pressure sensor was fixed on the wrist to detect the pulse of the human body in a calm state (Figure a) and after intensive activity (Figure c). Our sensor successfully detects a human heart rate of 93 bpm in the calm state (Figure b) and 113 bpm (Figure d) after intensive activity, and the pulse detection waveform has distinct P, T, and D peaks, which well match with the practical situation and can be further applied to the analysis of signals such as blood pressure . The pressure sensor is also fixed on the wrist to detect the wrist motion (Figure e).…”

“…Our sensor successfully detects a human heart rate of 93 bpm in the calm state (Figure 4b) and 113 bpm (Figure 4d) after intensive activity, and the pulse detection waveform has distinct P, T, and D peaks, which well match with the practical situation and can be further applied to the analysis of signals such as blood pressure. 53 The pressure sensor is also fixed on the wrist to detect the wrist motion (Figure 4e). Our sensor can accurately detect the resistance change from 198, 202, to 206 mΩ as the wrist bending degree increased from 0, 45, to 90°, respectively.…”

Highly Sensitive Fabric Sensors Based on Scale-like Wool Fiber for Multifunctional Health Monitoring

“…To date, several common types of flexible electronics are recognized, i.e., thin film, − hydrogel, , paper, − and fabric. − Among them, fabric sensors are considered to be the most competitive candidates because of their prominent advantages of natural interwoven structure, superior portability, wearing softness, and comfort. Generally, most pressure/strain fabric sensors have been designed mainly based on the mechanisms of piezoelectric, − capacitive, , triboelectric, , and piezoresistive sensing. − Among these sensing types, piezoresistive fabric sensors draw tremendous attention due to their simple fabrication process, convenient signal acquisition, and easy signal processing. Especially, functional fabrics constructed through integrating conductive active fillers including zero-dimensional (0D) metal nanoparticles, , one-dimensional (1D) nanowires/nanotubes, − and two-dimensional (2D) nanosheets − with soft insulating fabric are expected to be attractive alternatives for pressure/strain fabric sensors.…”

Additively Fabricated Electronic Skin with High Performance in Dynamic Sensing as Human Skin

“…Our group has fabricated an eutectic gallium− indium (EGaIn) flexible sensor with both high sensitivity and a wide detection range by the inner rinsing template method. 42 The sensor can detect real-time pulse, respiration, and blood pressure of a human body. This method offered a facile and economical approach for high-performance flexible sensor fabrication, which is very promising for modular fabrication of flexible skin.…”

“…However, the fabrication method is complicated and the equipment employed is expensive. Our group has fabricated an eutectic gallium–indium (EGaIn) flexible sensor with both high sensitivity and a wide detection range by the inner rinsing template method . The sensor can detect real-time pulse, respiration, and blood pressure of a human body.…”