Researches About Battery-free And Wireless Flexible Electrochemical Sensing Devices And Their Biomedical Applications

Recent years,the enormous progress in materials,designs,manufacturing processes,and electronics are driving the innovations in flexible electronics at a tremendous pace.Flexible electronics have been widely used in new research areas like wearable or implantable devices.Compared to traditional wearable and implantable devices,they are often flexible,ultrathin,and stretchable,which can be perfectly contact with soft surfaces like skin or organs,provide precise detections,and reduce the damages to human body.In the early days of the development of flexible electronics,the monitoring targets were mainly temperature,pressure,ECG and other physiological parameters.In recent years,with the development of electrochemical sensing technology,a series of wearable or implantable flexible electrochemical sensor devices have been developed to detect various biochemical substances in saliva,tears,sweat,tissue fluid,and blood,which have greatly expanded the application scope of flexible electronics.For flexible electrochemical sensing systems,the circuit is an indispensable part.However,most of the flexible electrochemical sensing systems lack circuit parts,and need wired connections with external electrochemical workstations to achieve data acquisition and processing,which greatly restricts the practical application of the system in wearable and implantable aspects.Recent years,many hybrid systems including both integrated circuits and electrodes have emerged.They can achieve complete electrochemical sensing functions.However,most of them require lithium battery for power supply,which restrict the flexibility and integration of the whole system.Near field communication (NFC) technology is a short-range wireless communication technology that can realize wireless power and data transmission through electromagnetic induction between antennas.By integrating the NFC module,the electrochemical sensing circuits,and the flexible electrode,it is possible to achieve the miniaturization,flexibility,and integration of the system while ensuring the complete electrochemical sensing function.Therefore,in this paper,we built a series of battery-free,wireless,and flexible electrochemical sensing systems based on NFC technology,electrochemical technology,and flexible electronics.These systems have been used in a series of innovative applications,such as exhaled breath monitoring,multiplexed sweat analysis,wound infection monitoring,wound treatment,heavy metal detections,etcThe main contents of this paper are as follows:1.Designed and constructed a battery-free and wireless epidermal electrochemical system with all-printed stretchable electrode array for multiplexed in situ analysis of various biological biofluids.Biological fluids such as sweat,urine and tear,are all complex liquid environments which contain abundant substances such as metabolites,electrolytes,neurotransmitters,etc.These substances contain abundant physiological information.In this study,based on NFC technology,electrochemical technology,and printed electronic technology,two wireless,passive,and flexible electrochemical patches were designed and constructed to achieve the quantitative detections of various biochemical targets in sweat,including glucose,Na+,K+,H+,Ca2+,and Cl-.The patches consist of a flexible printed circuit board and a stretchable electrode array.The sensing component of the system is a stretchable electrode array all-printed with soft polydimethylsiloxane (PDMS)and conductive silver nanowires.The electrodes show stable electrical properties during stretching,without serpentine designs.The electronic component of the system is a fully integrated flexible circuit board with near field communication module,which enables wireless energy harvesting and data transmission with smartphones.The system demonstrates good performance in real-time on-body sweat analysis for simultaneous quantitative detections of glucose,hydrogen,sodium,and potassium.This battery-free and wireless epidermal electrochemical system provides a simplified,miniaturized,and flexible solution for a wide range of biochemical platforms,including wearable and implanted bioelectronics.2.Designed and constructed a fully integrated battery-free and flexible electrochemical tag for on-demand wireless in situ monitoring of heavy metalsThe detection of heavy metals is important in environment monitoring,food safety,and health monitoring.However,there are no convenient and effective detection tools that can achieve rapid in situ detections of migrated heavy metals.In this study,a fully integrated battery-free and flexible electrochemical tag is developed based on square wave anodic stripping voltammetry(SWASV) technique,NFC technique,and printed electronic technique,for wireless in situ detections of heavy metal ions in various containers.The tag is flexible and miniaturized,which can be attchaed inside various containers for quantitative detections of lead and cadmium ions.According the the detection requirements,we designed an application on the smartphone.With the proximity of NFC-enabled smartphones,the device can be activated for wireless in situ heavy metal analysis.Then,the detection results can be wirelessly transmitted to the outside phone for viewing or further processing.The device provided an effective and convenient solution,which can be widely used in food safety and environment monitoring.3.Designed and constructed a passive and wireless tag sensor for semi-quantitative gas sensingCommercial NFC tags are low-cost,passive,wireless,and flexible,which can be wirelessly read by NFC-enabled smartphones.However,they can't be used for biochemical sensing.In this paper,we modified the circuits of the commercial NFC tags,and connected them with graphene-modified interdigital electrodes for semi-quantitive gas sensing.According the the detection requirements,we designed an application on the smartphone.With the proximity of NFC-enabled smartphone,the semi-quantitive detection of ethanol can be achieved.This smart tag sensor is cheap,wireless,passive,and flexible,which provides a new solotion for gas ensing.In the future,it can be applied for the detections of biomarkers in exhaled breath or volatile organic compounds(VOCs) in the environment.4.Designed and constructed a battery-free and wireless wound dressing for multiplexed infection monitoring and electrically controlled drug therapyInfection is a major health concern in wound management which can cause patients physical and emotional stress.In clinical practice,it's difficult and cost-expensive to evaluate the severity of wound infections,and relies heavily on the clinician experiences.The treatments of wound infection in clinical are mainly oral or continual local drugs with large dose,which are a big burden for liver and other organs.In this study,we introduced an NFC-enabled smart wound dressing,which can simultaneously detect multiple parameters of the wound,and provide electrically controlled drug delivery for infection treatment.The wound dressing consists of two layers.The top layer is an NFC-enabled flexible circuit board enabling wireless power harvesting,on site signal processing,temperature sensing,drug delivery controlling,and wireless data transmission.NFC-enabled smartphone is used to wirelessly power the device,get the detections results,and control the drug delivery.The bottom layer of the wound dressing is a stretchable electrode array based on polyimide (PI) substrate,including uric acid sensor,pH sensor,and a drug electrode.The serpentine wires and the PDMS encapsulation provide the high stretchability and biocompatibility of the electrode array which will have the direct contact with the wound sites.In the applications,we don't need to open the bandages at the wound site.While the wound is infected with bacteria,the changes of uric acid, pH value and temperature will be recorded by the wound dressing and wirelessly transmitted to the smartphone for a comprehensive judgement.If necessary,the command will be sent by the phone and the drug electrode will be activated to release on-demand antibacterial agents at the wound sites for precise treatment.This battery-free,wireless,and flexible wound dressing can be widely applied in clinical use for wound management.