Preparation And Application Of Wearable MXene-based Silk Protein Composite Membrane

With the increasing shortage of petroleum resources,it is more and more necessary to use biocomposite materials instead of traditional non-renewable electronic materials.Although traditional metal conductors and semiconductor materials have high carrier mobility,their rigid structural characteristics are significantly different from those of soft biological tissues,so they are not suitable for wearable electronic devices.In recent years,biomass conductive composites have been widely used in the fields of wearable electronic devices,tissue engineering,implantable medical devices,etc.,due to their advantages of environmental friendliness,wide range of sources,renewable and relatively cheap.Among many biomass materials,silk fibroin protein,as a unique structural protein,has multi-stage assembled micro and nano structure,excellent mechanical properties,biocompatibility and solution machinability,so that it has a broad application prospect in the field of wearable electronic devices.In this paper,the silk was degummed first,and the silk fibroin nanofibers were prepared by solvent incubation and ultrasonic crushing.In order to realize the electrical functionalization of biomass materials,the common preparation method is to compound it with conductive filler.As a functional nanomaterial with excellent properties,MXene is the general name of a class of two-dimensional transition metal carbides or nitrides.Among them,the most common Ti₃C₂ nanosheet has large surface area,excellent conductivity and biocompatibility.There are a large number of negatively charged groups on the surface of MXene,which will generate intermolecular hydrogen bond and electrostatic interaction with the hydroxyl functional group of tyrosine on silk fibroin protein,and enhance the interfacial interaction between adjacent MXene lamellae.MXene-based protein composite membrane was prepared by self-assembly of silk fibroin nanofibers and MXene mixed dispersions at low temperature and vacuum filtration.Supported by structural proteins,the composite membrane has continuous electron transmission channels,high porosity and large specific surface area,so it shows high conductivity and good mechanical flexibility,which is suitable for wearable electronic materials.Flexible wearable pressure sensor has attracted wide attention because of its superior real-time monitoring and flexible interaction with human body.Some highly sensitive and high-precision components in wearable electronic devices or robot systems will be affected by electromagnetic radiation during operation.In order to reduce the exposure of human body and electronic devices in electromagnetic wave environment,it is very necessary to develop wearable electronic materials and devices with electromagnetic wave protection function.In this paper,the structure sensitiveness strategy was used to use silk fibroin nanofibers as intercalation agents and bind with the active site of MXene nanosheets.The layer spacing of MXene nanosheets was adjusted by the content of silk fibroin nanofibers.The layer spacing of MXene nanosheets also changes under the action of external forces,and thus shows a high response to pressure signals.The pressure sensor made of composite membrane shows good stability under the continuous response of 500 seconds,and makes different responses to various motion scenes,and its response range can reach 100%.At the same time,the large lamellar spacing lengthens the transmission channel of incident electromagnetic wave,and the multistage network structure between different lamellar increases the absorption loss（SE_A）of electromagnetic wave.The total shielding efficiency（SE_T）of the prepared MXene biocomposite membranes in 8-26 GHz band is more than 60 d B.The silk fibroin composite membrane can also be used as an epidermal physiological electrode for the monitoring of human physiological electrical signals.The signal-to-noise ratio of the membrane is 23.12 d B,which is close to the performance of commercial Ag/Ag Cl gel electrodes.In vitro cell experiments were carried out on the composite membrane.After 3 days of cultured mouse fibroblasts on the composite membrane,the cells were observed to have good growth and complete morphology under the optical microscope,and showed similar activity compared with the control group.Finally,the degradation test was carried out,and the composite film was completely degraded after soaking in 2%H₂O₂solution for 2 days.The MXene-based protein biocomposite membrane prepared in this paper provides a new idea for the development of green and sustainable wearable electronic materials.