Multistrand Twisted Triboelectric Kevlar Yarns for Harvesting High Impact Energy, Body Injury Location and Levels Evaluation

Abstract Developing ultrahigh‐strength fabric‐based triboelectric nanogenerators for harvesting high‐impact energy and sensing biomechanical signals is still a great challenge. Here, the constraints are addressed by design of a multistrand twisted triboelectric Kevlar (MTTK) yarn using conductive and non‐conductive Kevlar fibers. Manufactured using a multistrand twisting process, the MTTK yarn offers superior tensile strength (372 MPa), compared to current triboelectric yarns. In addition, a self‐powered impact sensing fabric patch (SP‐ISFP) comprising signal acquisition, processing, communication circuit, and MTTK yarns is integrated. The SP‐ISFP features withstanding impact (4 GPa) and a sensitivity and response time under the high impact condition (59.68 V GPa−1; 0.4 s). Furthermore, a multi‐channel smart bulletproof vest is developed by the array of 36 SP‐ISFPs, enabling the reconstruction of impact mapping and assessment of body injury location and levels by real‐time data acquisition. Their potential to reduce body injuries, professional security, and construct a multi‐point personal vital signs dynamic monitoring platform holds great promise.


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Table S1.Energy conversion efficiency of a SP-ISFP.

Illustrative calculation of energy conversion efficiency
One of the unique advantages of triboelectric technology in bulletproof vest is that triboelectric materials can convert impact energy into electrical energy, thus reducing the probability of the wearer being exposed to external injuries.Since bulletproof vest is mostly converted to electricity from the impactor's kinetic energy on impact.
Therefore, we tested the energy conversion efficiency of a SP-ISFP at different speeds.
The mass of the object is 100g and the area of a SP-ISFP is 2.5×10 -3 m 2 .The energy conversion efficiency was calculated using the formula shown in below, as shown in Table S1 below.
Where m is the mass of the impactor, v is the instantaneous velocity when the impactor hits the SP-ISFP.U is the open-circuit voltage and I is the short-circuit current.

Figure S1 .
Figure S1.The process of manufacturing MTTK yarn.

Figure S2 .
Figure S2.Photographs showing the flexibility of MTTK yarn.

Figure S3 .
Figure S3.Comparison of air permeability between the SP-ISFP and several

Figure S4 .
Figure S4.Contact models of six dielectric materials and their effects on the output of

Figure S7 .
Figure S7.Charging capacity of the SP-ISFP at different the external forces.

Figure S8 .
Figure S8.Dependence of the Resistance and peak power at different accelerations.

Figure S9 .
Figure S9.Electrical output performances of SP-ISFP at different the external forces.

Figure S10 .
Figure S10.The interdependence between the number of front-end layers and the

Figure S11 .
Figure S11.Simulation of the relationship between the number of layers at the front-

Figure S12 .
Figure S12.Pressure distribution of the array of 36 SP-ISFPs, predicted by finite

Figure S13 .
Figure S13.The original waveform diagram of the stick acting fifty times.

Figure S14 .
Figure S14.The original waveform diagram of the hammer acting fifty times.

Figure S15 .
Figure S15.The original waveform diagram of the arrow acting fifty times.

Figure S16 .
Figure S16.The original waveform diagram of the fist acting fifty times.

Figure S17 .
Figure S17.The original waveform diagram of the knife acting fifty times.

Figure S18 .
Figure S18.Training set confusion matrix for weapon identification (accuracy of

Figure S19 .
Figure S19.Detail of SP-ISTPs voltage signal at 9 main force positions.

Figure S21 .
Figure S21.Training set confusion matrix for impact grade judgment (accuracy of

Figure S1 .
Figure S1.The process of manufacturing MTTK yarn.a) The soak, dry and twist

Figure. S4 .
Figure.S4.Contact models of six dielectric materials and their effects on the

Figure S5 .
Figure S5.Comparison of electrical output of SP-ISFP under different

Figure S7 .
Figure S7.Charging capacity of the SP-ISFP at different the external forces.a) Charging voltage of the different capacitances (10 F, 22 F, 47 F, and 100 F) at the force of 225 kPa.b) Charging voltage of the different capacitances (10 F, 22 F, 47 F, and 100 F) at the force of 573 kPa.c) Charging voltage of the different capacitances (10 F, 22 F, 47 F, and 100 F) at the force of 769 kPa.d) Charging voltage of the different capacitances (10 F, 22 F, 47 F, and 100 F) at the force of 1019 kPa.e) Charging voltage of the different capacitances (10 F, 22 F, 47 F, and 100 F) at the force of 1274 kPa.f) Summary diagram of charging capacity of SP-ISFP

Figure S9 .
Figure S9.Electrical output performances of SP-ISFP at different the external

Figure S10 .
Figure S10.The interdependence between the number of front-end layers and the

Figure S11 .
Figure S11.Simulation of the relationship between the number of layers at the

Figure S12 .
Figure S12.Pressure distribution of the array of 36 SP-ISFPs, predicted by finite

Figure S13 .
Figure S13.The original waveform diagram of the stick acting fifty times.

Figure S14 .
Figure S14.The original waveform diagram of the hammer acting fifty times.

Figure S15 .
Figure S15.The original waveform diagram of the arrow acting fifty times.

Figure S16 .
Figure S16.The original waveform diagram of the fist acting fifty times.

Figure S17 .
Figure S17.The original waveform diagram of the knife acting fifty times.

Figure S18 .
Figure S18.Training set confusion matrix for weapon identification (accuracy of

Figure S21 .
Figure S21.Training set confusion matrix for impact grade judgment (accuracy of