Artificial Intelligence Meets Flexible Sensors:Emerging Smart Flexible Sensing Systems Driven by Machine Learning and Artificial Synapses

The recent wave of the artificial intelligence(AI)revolution has aroused unprecedented interest in the intelligentialize of human society.As an essential component that bridges the physical world and digital signals,flexible sensors are evolving from a single sensing element to a smarter system,which is capable of highly efficient acquisition,analysis,and even perception of vast,multifaceted data.While challenging from a manual perspective,the development of intelligent flexible sensing has been remarkably facilitated owing to the rapid advances of brain-inspired AI innovations from both the algorithm(machine learning)and the framework(artificial synapses)level.This review presents the recent progress of the emerging AI-driven,intelligent flexible sensing systems.The basic concept of machine learning and artificial synapses are introduced.The new enabling features induced by the fusion of AI and flexible sensing are comprehensively reviewed,which significantly advances the applications such as flexible sensory systems,soft/humanoid robotics,and human activity monitoring.As two of the most profound innovations in the twenty-first century,the deep incorporation of flexible sensing and AI technology holds tremendous potential for creating a smarter world for human beings.

Interfacial Bonding Mechanism and Mechanical Performance of Continuous Fiber Reinforced Composites in Additive Manufacturing

The additive manufacturing of continuous fiber composites has the advantage of a high-precision and efficient forming process,which can realize the lightweight and integrated manufacturing of complex structures.However,many void defects exist between layers in the printing process of additive manufacturing;consequently,the bonding performance between layers is poor.The bonding neck is considered a key parameter for representing the quality of interfacial bonding.In this study,the formation mechanism of the bonding neck was comprehensively analyzed.First,the influence of the nozzle and basement temperatures on the printing performance and bonding neck size was measured.Second,CT scanning was used to realize the quantitative characterization of bonding neck parameters,and the reason behind the deviation of actual measurements from theoretical calculations was analyzed.When the nozzle temperature increased from 180 to 220℃,CT measurement showed that the bonding neck diameter increased from 0.29 to 0.34 mm,and the cross-sectional porosity reduced from 5.48%to 3.22%.Finally,the fracture mechanism was studied,and the influence of the interfacial bonding quality on the destruction process of the materials was determined.In conclusion,this study can assist in optimizing the process parameters,which improves the precision of the printing parts and performance between the layers.

Nanoscale Wire Bonding of Individual Ag Nanowires on Au Substrate at Room Temperature

The controllable wire bonding of individual Ag nanowires onto a Au electrode was achieved at room temperature. The plastic deformation induced by pressure using nanoindentation could break the protective organic shell on the surface of the Ag nanowires and cause atomic contact to promote the diffusion and nanojoining at the Ag and Au interface. Severe slip bands were observed in the Ag nanowires after the deformation. A metallic bond was formed at the interface, with the Ag diffusing into the Au more than the Au diffused into the Ag. This nanoscale wire bonding might present opportunities for nanoscale packaging and nanodevice design.

Diffusion Bonding of Tungsten to Copper and Its Alloy with Ti Foil and Ti/Ni/Ti Multiple Interlayers

Ti foil and Ti/Ni/Ti multiple interlayers were selected for the bonding of tungsten to copper and CuCrZr alloy.Theeffects of processing conditions on the microstructures and shear strength of the joints were investigated.When Tifoil is used for bonding of tungsten to pure copper but not transformed into liquid solution during the holding time,the strength of the joints is relatively low because of the multiple compound layers with brittleness formed in thebonding zone.The strength of the joints increases significantly if the Ti foil is transformed into liquid solution and ismostly extruded out of the bonding zone.The same phenomena are found in the case when Ti/Ni/Ti multi-interlayersare used for bonding tungsten to CuCrZr alloy.

A wireless, implantable optoelectrochemical probe for optogenetic stimulation and dopamine detection

Physical and chemical technologies have been continuously progressing advances in neuroscience research.The development of research tools for closed-loop control and monitoring neural activities in behaving animals is highly desirable.In this paper,we introduce a wirelessly operated,miniaturized microprobe system for optical interrogation and neurochemical sensing in the deep brain.Via epitaxial liftoff and transfer printing,microscale light-emitting diodes(micro-LEDs)as light sources and poly(3,4-ethylenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)-coated diamond films as electrochemical sensors are vertically assembled to form implantable optoelectrochemical probes for real-time optogenetic stimulation and dopamine detection capabilities.A customized,lightweight circuit module is employed for untethered,remote signal control,and data acquisition.After the probe is injected into the ventral tegmental area(VTA)of freely behaving mice,in vivo experiments clearly demonstrate the utilities of the multifunctional optoelectrochemical microprobe system for optogenetic interference of place preferences and detection of dopamine release.The presented options for material and device integrations provide a practical route to simultaneous optical control and electrochemical sensing of complex nervous systems.

Ultrasound-Assisted Transient Liquid Phase Bonding of Magnesium Alloy Using Brass Interlayer in Air

The microstructure evolution and oxide film behavior in ultrasound-assisted transient liquid phase（U-TLP） bonding of Mg alloy were investigated by applying different ultrasonic time at 460？C with brass interlayer in air. The results indicated that with increasing ultrasonic time, brass interlayer disappeared gradually and the Mg-Cu-Zn eutectic compounds were formed. The eutectic compounds in the joint decreased as the ultrasonic time increased further. The oxide removal process was divided into four steps. Continuous oxide film at the interface was partially fractured by ultrasonic vibration,and then suspended into liquid by undermining eutectic reaction. After that, the suspended oxide film was broken into small oxide fragments by ultrasonic cavitation effect, which was finally squeezed out of the joint by ultrasonic squeeze action. In addition, the mechanical properties of the joints were investigated. The maximum shear strength of the joint reached 105 MPa, which was 100% of base metal.

Interfacial Structure and Formation Mechanism of Ultrasonic-assisted Brazed Joint of SiC Ceramics with Al—12Si Filler Metals in Air

Ultrasonic-assisted brazing of SiC ceramics was performed by filling with an Al-12Si alloy at a low tem- perature of 620 ℃ in air. The interracial characteristics and formation mechanism were investigated. The joint shear strength reached 84-94 MPa using the ultrasonic time of 2-16 s. The fracture morphology showed that the fracture path initiated and propagated in the joint alloy. The thin film of amorphous SiO2 that formed on the SiC surface was non-uniformly decomposed and diffused into the liquid Al-12Si alloy under the cavitation erosion effect of ultrasound. Abnormal isolated blocks of A12SiO5 compounds formed at the interface between Al-12Si and a thicker SiO2 layer formed during the thermal oxidation treatment of the SiC ceramic. The SiO2 layer on the SiC ceramic did not hinder or impair the wetting and bonding process, and a stronger bond could form between Al-12Si and SiO2 or SiC in ultrasonic- assisted brazing.