Smart Fibers for Self‑Powered Electronic Skins

Smart fibers are considered as promising materials for the fabrication of wearable electronic skins owing to their features such as superior flexibility,light weight,high specific area,and ease of modification.Besides,piezoelectric or triboelectric electronic skins can respond to mechanical stimulation and directly convert the mechanical energy into electrical power for self-use,thereby providing an attractive method for tactile sensing and motion perception.The incorporation of sensing capabilities into smart fibers could be a powerful approach to the development of self-powered electronic skins.Herein,we review several aspects of the recent advancements in the development of self-powered electronic skins constructed with smart fibers.The summarized aspects include functional material selection,structural design,pressure sensing mechanism,and proof-to-concept demonstration to practical application.In particular,various fabrication strategies and a wide range of practical applications have been systematically introduced.Finally,a critical assessment of the challenges and promising perspectives for the development of fiber-based electronic skins has been presented.

Field Sensing Characteristic Research of Carbon Fiber Smart Material

In order to research the field sensing characteristic of the carbon fiber smart material, the Tikhonov regularization principle and the modified Newton-Raphson(MNR) algorithm were adopted to solve the inverse problem of the electrical resistance tomography(ERT). An ERT system of carbon fiber smart material was developed. Field sensing characteristic was researched with the experiment. The experimental results show that the specific resistance distribution of carbon fiber smart material is highly consistent with the distribution of structural strain. High resistance zone responds to high strain area, and the specific resistance distribution of carbon fiber smart material reflects the distribution of sample strain in covering area. Monitoring by carbon fiber smart material on complicated strain status in sample field domain is realized through theoretical and experimental study.

Three dimensional photovoltaic fibers for wearable energy harvesting and conversion

As the development of smart electronics, self-powered sources have been attracting increasing attention.This review summarizes research progress of photovoltaic fibers and their integrated power sources with multi-stage energy conversion. Recent development of three dimensional photovoltaic fibers is glanced with special attention to structure design and materials of typical photovoltaic types（inorganic, organic,dye/quantum dot sensitized and perovskite solar cells）. The application of carbon materials in fiber energy is focused as it is a hot topic recently. The hybrid energy systems based on fiber solar cells and fiber supercapacitors, fiber batteries and fiber nanogenerators are summarized together with hybrid energy textiles. This review provides a macroscopic view of novel energy fibers and will attract research interest in flexible/wearable fiber electronics and energy textiles.

Modification of Interfacial Performance of Fiber Bragg Grating Embedded in the Composite Materials

The interfacial performance of the Fiber Bragg grating（FGB） embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine（Pentaethylenehexamine, PEHA） was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength（77%） were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.

Predicting the Thermal Behavior in Functional Textile Fibers Having Embedded Electronics

In this paper,both steady-state and transient thermal simulations were performed on functional fibers having an embedded electronic chip acting as a heat source.Simulations were conducted for a range of different fiber materials and arbitrary fiber cross-sectional shapes.We show that under steady-state heating conditions,the thermal response for any arbitrary fiber shape and fiber material system was convection dominated regardless of the effective thermal conductivity of the fiber,and that the corresponding temperature rise within the fiber can be predicted analytically allowing for the maximum temperature to be estimated for any known heat load and fiber geometry.In the case of transient heating,we show that for pulsed power operation of the embedded electronic device,the maximum temperature reached in the fiber is always greater than the maximum temperature of the equivalent steady-state average power.However,high peak powers can be safely achieved if the power-on pulse time and duty cycle are selected to limit the maximum temperature reached in the fiber.Based on the results from the transient simulations,a set of criteria was developed to determine whether the operating conditions would be:(1)allowable for the fiber system,thus requiring no transient simulations,(2)requiring a transient simulation to verify that the maximum temperature is acceptable,and(3)the operating conditions are too severe and device operation at these conditions are not practical.