| Inorganic oxide films,with their diverse elemental compositions and rich structural morphologies,exhibit a wide range of physical and chemical properties and can be used across various domains of the electronics industry.As an emerging technology,flexible electronics not only hold significant potential in fields such as virtual reality and the Internet of Things but also drive the shift towards smarter daily living.Relying on the established industrial chain of inorganic oxide thin films to develop flexible electronic devices allows for enhancing device performance through the application of highperformance inorganic oxide thin films,and the transformation from laboratory research to market application can be accelerated.However,the intrinsic rigidity of inorganic oxide thin films limits their application in flexible devices,necessitating the development of strategies for flexibility to reconcile the contradiction between the rigidity of the films and the flexibility requirements of the devices.The fundamental approach to the flexibility of devices based on inorganic oxide thin films involves first fabricating the films on traditional rigid substrates,followed by their transfer onto flexible substrates through delamination and transfer printing,and finally conducting rational mechanical structural design and patterning to achieve overall device flexibility.In this process,the growth and transfer of films and the design and fabrication of devices complement each other,requiring holistic and coordinated optimization.The films not only need to grow with high quality but also be capable of delamination and transfer printing.The corresponding transfer process must minimize damage to the film structure to avoid impacting the final device performance.In device design and fabrication,controlling the electro-mechanical coupling properties through rational construction of device structures is essential to avoid mechanical failure during deformation while achieving the desired functionality and performance.This dissertation systematically explores the preparation of high-quality inorganic oxide thin films,methods for integrating film flexibility,and the design and fabrication of flexible devices based on inorganic oxide thin films.Specific studies were conducted using titanium dioxide(TiO2)and barium titanate(BTO)thin films to construct various flexible electronic devices.Additionally,the potential applications of these devices in biological contexts were explored.The main contents are as follows:(1)The preparation process was improved to obtain high-quality flexible inorganic oxide films.Highly oriented TiO2 films and large-area(2-inch diameter)epitaxial BTO films were successfully prepared using the polymer-assisted deposition(PAD)method.In the preparation of flexible and standalone thin films,the difference in hydrophilicity between the substrate and the film was fully utilized to effectively avoid the potential mechanical damage of delamination speed on films in the standard transfer printing process.The programmable transfer of TiO2 film with an array pattern was achieved with a liquid-assisted transfer printing process,and large-area BTO films were transferred by using an improved polymethyl methacrylate-assisted transfer printing process.The films maintain consistency in structure,morphology,and performance before and after the transfer printing process,indicating the minimal impact of the transfer printing process on the films.Furthermore,a biaxial strain sensor based on BTO films capable of synchronously monitoring orthogonal vibrations was fabricated and exhibited excellent mechanical reliability and stability even after 1000 bending cycles.(2)The free-standing inorganic oxide films were integrated into the flexible electrochemical sensors to allow non-invasive and accurate monitoring of important biochemical markers in biological fluids.The flexible electrochemical sensor based on highly oriented TiO2 films can sensitively detect tyrosine(Tyr,0.126μA/(μM·cm2)),paracetamol(PA,0.0841(μA/(μM·cm2)),and dopamine(DA,1.390 μA/(μM·cm2)),and retains stable electrochemical sensing performance even under mechanical deformations such as bending and twisting.Combining this electrochemical sensor with microfluid channels,a dual-channel skin patch was fabricated and capable of accurate and real-time monitoring Tyr and PA simultaneously by deriving from the amperometric current density obtained under two oxidation potentials.Moreover,the potential application of the skin patch for daily health monitoring was validated through real-time,non-invasive,and wireless monitoring of Tyr concentration in human sweat.On another hand,the construction of a calibration matrix has enabled the decoupling of environmental pH values and DA concentrations from a single electrochemical measurement.Further integrating this electrochemical sensor array with a wireless transmission unit has led to the development of a smart diaper,which successfully enables effective and wireless monitoring of urine distribution and biomarker levels in urine.(3)The phase composition of inorganic oxide films was optimized to enhance their photo-transformation capabilities and effective operational range.Through the cyclic PAD process,the structure of the Tiμ2 films gradually transitioned from a pure anatase phase to a dual phase as the cycle number increased.Compared to single-phase TiO2 films,the dual-phase TiO2 films exhibited significant improvements in photocatalytic degradation efficiency,antibacterial rate,and photoelectric current response.Moreover,an ultraviolet monitoring sensor based on dual-phase TiO2 films with optimized ratios maintained good mechanical stability and image recognition capability even after 4000 bending cycles.Moreover,the photocatalytic performance of TiO2 films was further extended from the ultraviolet to the visible light region by leveraging the surface plasmon resonance effect introduced by gold(Au)modification,displaying outstanding broadspectrum antibacterial performance under visible light.With the optimized Au modification,a respiration monitoring sensor with fast response time(0.71 s)and recovery time(1.06 s)was successfully fabricated,allowing long-term,real-time,and wireless monitoring of different breathing characteristics.Moreover,this respiration monitoring sensor employed a unique mechanical sensing mechanism,effectively avoiding interference from external factors such as gas composition,humidity,temperature,stress,and strain,enhancing its stability and accuracy. |
