| Flexible wearable electronics bring a lot of convenience to people’s modern smart life.As the core component of wearable products,the sensor needs to be constantly charged and powered,which is not conducive to long-term use.Thermoelectric conversion-based self-powered components can collect human thermal energy to achieve the purpose of energy supply to the sensor.Conventional thermoelectric materials are mostly rigid materials such as semiconductors and metal conductors,and are mostly toxic and not suitable for flexible electronic devices.Ionic conductor-based thermoelectric conversion materials have good flexibility and thermoelectric conversion performance,and are expected to be used in self-powered sensors and power supply for flexible electronic devices.However,the following problems exist in the practical application of ionic hydrogel thermoelectric materials:（1）The conductivity and Seebeck coefficient of ionic hydrogel are low,and the thermoelectric conversion efficiency is poor.（2）The environmental tolerance of ionic hydrogel is poor,and it is easy to lose water and freeze.In this paper,polyacrylamide/calcium alginate/lithium sulfate self-powered strain sensors and polyacrylamide/lithium chloride ionic hydrogel thermoelectric generators were successfully prepared using inexpensive polyacrylamide and sodium alginate as flexible substrates and different lithium salts as conductive media,mainly as follows:（1）A high tensile quasi-solid hydrogel polyacrylamide/calcium alginate/lithium sulfate was synthesized by polymerization and physical crosslinking.It can be used as a wearable self-powered human motion sensor,which shows 2800%elongation at break and good strain sensitivity（GF=4,when the strain is 200%）and detects the movement and sound of human body.Further,the hydrogel-based sensor can harvest the human body heat and generate a thermovoltage to drive the sensor directly,which exhibits an impressive gigantic Seebeck coefficient of approximate 11.5 m V K-1 at ambient temperature.Combining the merits of flexibility,environment friendly,sensitivity and thermoelectric performance at room temperature range together,the hydrogel-based sensor will offer amble opportunities to numerous self-powered sensor applications like wearable electronics,sports and health.（2）.By solvent replacement method,an ionic hydrogel thermoelectric generator（ITEG）is obtained,which has high thermoelectric performance,excellent water retention,freezing resistance and self-regeneration ability,and remains non-freezing at low temperature（-20 oC）.The obtained ITEG can maintain the original water content at ambient temperature（29 oC,65%RH）for 7 days and keep unfreezing at low temperature（-20 oC）.It can even be self-regenerated and recovered to the original state after a water loss in high temperature conditions.Furthermore,a giant ionic Seebeck coefficient of 11.3 m V K-1 and an impressive power density of 167.90m W m-2 are achieved under a temperature difference of 20 oC.A high-power density of 60.00m W m-2 also can be maintained even at-15 oC.In addition,the ZTi of the ITEG can be achieved as 0.31 at room temperature,showing an outstanding heat-to-electric conversion efficiency.After drying and re-generation,ITEG-re even possesses a higher ionic Seebeck coefficient of11.8 m V K-1.Successful lighting of LED and charging of capacitors demonstrate that the ITEG can provide continuous energy supply,showing its great potential in powering flexible electronics. |
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