Achieving macroscale superlubricity with ultra-short running-in period by using polyethylene glycol-tannic acid complex green lubricant

Superlubricating materials can greatly reduce the energy consumed and economic losses by unnecessary friction.However,a long pre-running-in period is indispensable for achieving superlubricity;this leads to severe wear on the surface of friction pairs and has become one of the important factors in the wear of superlubricating materials.In this study,a polyethylene glycol-tannic acid complex green liquid lubricant(PEG10000-TA)was designed to achieve macroscale superlubricity with an ultrashort running-in period of 9 s under a contact pressure of up to 410 MPa,and the wear rate was only 1.19×10^(–8)mm^(3)·N^(−1)·m^(−1).This is the shortest running-in time required to achieve superlubricity in Si_(3)N_(4)/glass(SiO_(2)).The results show that the strong hydrogen bonds between PEG and TA molecules can significantly reduce the time required for the tribochemical reaction,allowing the lubricating material to reach the state of superlubrication rapidly.Furthermore,the strong hydrogen bond can share a large load while fixing free water molecules in the contact zone to reduce shear interaction.These findings will help advance the use of liquid superlubricity technology in industrial and biomedical.

Concealed Wireless Warning Sensor Based on Triboelectrification and Human-Plant Interactive Induction

With the continuous development of artificial intelligence,the demand for sensors with simple preparation and strong concealment continues to increase.However,most of the high-sensitivity sensors have complex manufacturing methods,high costs,and single functions.In this paper,a sensitive motion sensor based on the triboelectric interaction between a living plant and the human body was designed to detect the real-time movements of human beings and provide danger warning.A certain relationship exists between the triboelectric signal and the distance between the plant and the human body,with effective signals being detected in the range of 1.8 m.In addition,the triboelectric signal generated by each person is unique like a fingerprint,which can be used for biometrics.On the basis of the triboelectric signal,a wireless character entry warning system is designed.This sensor can not only send out a wireless warning signal at a specific distance but also allow one to receive the warning information synchronously on a mobile phone in real time.The wireless movement sensor receives signals through a living plant,and it has the characteristics of convenient use,strong concealment,and shielding difficulty.This sensor has the potential to be widely used in person recognition,danger warning,and motion monitoring.

New starch capsules with antistatic,anti-wear and superlubricity properties

Adsorption of drug powder is caused by triboelectrification on the surface of starch capsule during filling process.Furthermore,high wear rate and poor water lubricity also hinder the further practical applications of traditional starch capsule.To solve these problems,a glycerol-modified starch capsule with perfect anti-triboelec-trification and enhanced lubrication performance was fabricated.Hydrogen bond between glycerol and starch molecules could reduce the bound water content on the capsule surface and thus realizes anti-triboelectrification.By adding glycerol,a three-tier structure composed of starch-glycerol-water is formed through hydrogen bonding on the surface of the starch film,which has been proven to be favorable for lubrication performance.When 5% glycerol is added,the short-circuit current(I_(sc))of starch-based triboelectric nanogenerator(TENG)is reduced by 86%,and the wear volume of the starch film is reduced by 89%.Underwater lubrication condition,the lubrication performance of the starch-glycerol film can reach the super lubricated level with a friction coefficient of about 0.005.This work provides a new route to obtain modified starch capsules with improved anti-triboelectrification property,reduced wear rate and superlubricity property.