Preparation Of 2-D Carbide Ti₃C₂T_x Fiber And Its Application In Flexible Thermoelectricity

In the past few decades,with the development of nanomaterials and microelectronic technology,small,low-power,multifunctional electronic products,especially micro wearable devices,have been rapidly developed.However,most of the batteries that power products either need to be replaced or recharged regularly,and the limited lifetime and frequent replacement requirements diminish the usefulness of wearables.In view of this,self-powered equipments had became a hot research direction in recent years in order to facilitate the continuous monitoring of data in a long time.The human body is a constant source of outward heat.Converting just 1%of the heat produced by the human body into electricity would be enough to power most portable electronics.Thermoelectric generators can provide permanent DC power to electronics by collecting and converting heat emitted by the human body and are easy to replace and maintain.The intrinsic rigidity,brittleness and weight of high performance inorganic thermoelectric materials make it difficult to effectively fibrosis.Organic thermoelectric materials have excellent flexibility,but there are some problems such as low thermoelectric conversion rate and poor stability.Organic/inorganic composite thermoelectric materials can effectively balance the flexibility and thermoelectric conversion efficiency of thermoelectric devices,but the existing composite materials are limited by the strong coupling between Seebeck coefficient,conductivity and thermal conductivity,and thin film thermoelectric devices are difficult to match the direction of heat flow between human body and the environment.Therefore,in this paper,Ti₃C₂T_xMXene based stretchable composite fiber was constructed by microfluidic limited space self-assembly technology by preparing Ti₃C₂T_xMXene-based semiconductor material with high conductivity,and the preparation process and material properties were discussed and characterized in detail.Stretchable flexible thermoelectric devices are designed and assembled to better match the direction of heat flow between human body and environment and wearable mechanical stability.The specific research content includes the following two aspects:1.Preparation and properties of 2D Ti₃C₂T_xMXene and its composite fibers.High quality Ti₃C₂T_xMXene nanosheets with large area and ultra-thin were prepared by in situ HF etching method,and were quantitatively doped with thermoplastic polyurethane particles（TPU）to obtain spinning stock.Mxene-TPU composite fibers were prepared by microfluidic wet spinning technology.The pore size,mechanics,electrical conductivity,thermal conductivity and tensile properties of fiber materials can be controlled by adjusting the proportion of composite materials and technological conditions.The composite fiber with 60 wt.%MXene content has 434%elongation,1.25×10³S·m^-1conductivity,0.19 W·m^-1·K^-1thermal conductivity and Seebeck coefficient of-8.0μV·K^-1.2.Construction and performance of two-dimensional Ti₃C₂T_xMXene composite fiber thermoelectric devices.Considering the application needs of skin-friendly and soft in real life,the above multiple MP-60 composite fibers were integrated with breathable and stretchable elastic fabric to form a flexible wearable thermoelectric sensor,and the thermoelectric performance was tested.The output voltage,current and power were recorded under different temperature differences,and it was found that there was a good linear relationship between voltage and current and temperature difference.The power and temperature difference show a quadratic relationship.At room temperature,when the device is worn on the human body,when the number of fibers is 24,the output voltage can be up to 3.6 m V.In addition,further research shows that the output voltage and power can be improved by increasing the temperature difference between the cold and hot ends of the device or integrating more composite fibers.Moreover,the low resistance change rate at low tensile rate proves its electrical stability,which has great potential for powering wearable electronics in the future.