Research On Flexible Strain Sensor Based On Femtosecond Laser Direct Writing Of Gold Nanoparticles

For intelligent wearable electronic technology,flexible sensors can perfectly adapt to the uneven surface of skin and clothing without hindering human activities,sense signals rapidly and accurately and have simple and quick operation.It has great application potential in human medical treatment,motion recognition,human-computer interaction and other fields.s the main branch of smart wearable flexible sensor,flexible strain sensor has attracted much attention in recent years.Most of the traditional strain sensors are based on metal and semiconductor materials.Since the sensitivity of the metal strain sensor only depends on the geometric effect of the metal materials,the sensitivity of the sensor(Gauge Factor: GF)is poor,usually between 2 and 6.The strain sensor based on semiconductor materials has high sensitivity due to their unique piezoresistive effect.However,due to their poor tensile performance,small detection range and high manufacturing cost,it cannot meet the needs of extensive applications.With the development of flexible electronic technology and fabrication technology of nanomaterials,new flexible strain sensors based on various functional nanomaterials and flexible substrates have been widely concerned by researchers.Compared with the traditional strain sensor,the new flexible strain sensor has better tensile performance,higher sensitivity and faster dynamic strain sensing ability.However,at present,most researchers mainly pay attention to improving the performance of flexible strain sensor,and there is little related work on how to achieve the miniaturization of high-performance flexible strain sensors.However,the miniaturization of sensors is of great significance to the development of sensor applications in many fields.The micro flexible strain sensor with small size has many unique advantages compared with the macro sensor.The micro flexible strain sensor has low power consumption,wide applications,high comfort level and portability,and is easy to realize array sensing and distributed measurement.In the meantime,the constant reduction of the size of sensors is conducive to the integration of different types of sensors to achieve a powerful sensor system.t present,the technologies to fabricate the micro flexible strain sensor mainly includes photolithography,printing electronic technology and laser processing technology.Photolithography is widely used in fabrication of high-precision and complex microstructures.However,the preparation process is complicated,the selection of sensing materials is limited,and the flexible positioning and size selection with template dependence are limited.Printed electronics technology has simple process and low cost,and can quickly realize diversified microstructure.However,the accuracy of fabrication is limited and the process of configuration printing ink also need to add a variety of toxic chemicals.In order to solve the above problems,this paper proposes to use femtosecond laser direct writing technology with high processing accuracy,controllable computer programming,no mask and toxic chemicals to prepare the microwire flexible strain sensor with excellent performances.We apply it to human health signal detection.The main research work is as follows:Firstly,the gold nanoparticle thin film flexible strain sensor was fabricated by drop-coating and high temperature annealing.The strain sensing performance of the sensor are studied.Then,a microwire flexible strain sensor was fabricated by femtosecond laser direct writing.The laser processing parameters were constantly adjusted to optimize and improve the sensing performance of the microwire flexible strain sensor,which are significantly improved compared with the macro gold nanoparticle thin film strain sensor.The gold nanoparticle microwire contains a large number of nanoparticle short chains.The reversible connections between the short chains enable the flexible strain sensor to have more excellent strain sensing performance.The sensitivity of the strain is up to 70.31,the linearity is 0.999,the response time is 160 ms,and the recovery time is 120 ms.Sensors can sense various dynamic strains in real time.Next,the applications of the microwire strain sensor in human health monitoring were explored.Sensors attached to different parts of the human body can realize the monitoring of human health signals.For example,sensors attached to the surfaces of the human finger,wrist and cervical vertebra can detect the motion of the joints.ttached to the outside of the throat,they can detect vocal cord vibrations for speech recognition.ttached to the radial artery of the wrist,the pulse waveform can be detected for the early prevention and diagnosis of cardiovascular diseases.