| Flexible aptamer-based graphene field-effect transistor is capable of conforming to underlying surfaces(e.g.,those of human organs or tissues)and offer the capability of biomarker detection in human biofluids or blood,which benefits from its sample structure,high integration,high sensitivity and fast sensing response,thereby showing the crucial research significance and application values in fields of disease prevention and diagnosis devices and wearable or implantable biosensors.However,the flexible aptamer-based graphene field-effect transistor is still an emerging field at present,and its researches are mainly conceptual model demonstration.The influence of mechanical deformation on electrical parameters and detection performance of flexible biosensors still lacks in-depth quantitative theoretical analysis and experimental testing.In addition,human biofluids and blood contain abundant impurities and blood cells,and the content of biomarkers is small,which requires the high detection performance and anti-interference ability of the flexible biosensor.However,the existing aptamer-based graphene field-effect transistor possesses several problems such as the poor limit of detection,simple detection environment and inability to be reused,which makes it difficult for practical applications.Aiming at the currently insufficient theoretical and application of the flexible aptamer-based graphene field-effect transistor biosensor under mechanical deformation,this work studies the electrical properties of the graphene field-effect transistor and effect of deformation on the lattice and energy band structure of the single-layer graphene conducting channel,therefore,a mathematical model of the quantitative relationship between the strain ε and carrier mobility μ is established.By introducing the concentration of impurity molecules to the classical Hill equation and combining the relationship between εand μ,a mathematical model of the effect of ε on the relationship between the concentration of target molecules and the drain-source current of the biosensor is established,which provides theoretical support for the following flexible biosensors processing and detection.Based on the established mathematical model of strain and electrical properties and detection signals,a flexible and ultrathin aptamer-based graphene field-effect transistor biosensor with the thickness of 2.5 μm has been developed to realize the capability of conforming to underlying surface.Also,the transconductance and carrier mobility of the sensor on the hole and electron branch,as well as the transfer characteristic curves of sensing responses and binding affinity between aptamer and protein,are tested through the bending,twisting,stretching and combined mechanical deformations,demonstrating that the flexible aptamer-based graphene field-effect transistor biosensor maintains the consistent properties under various mechanical deformation.In addition,the mechanical durability of the device is verified through cyclic bending,twisting and stretching tests(up to 500 cycles).The flexible sensor still remains the consistent electrical properties and accurate biomarker detection throughout tests.Developing a flexible aptamer-based graphene field-effect transistor biosensor based on a polymer isolated layer,which inhibits the interference of sensing signals caused by non-specific adsorption of non-target molecules on the graphene surface,enabling the accurate biomarker detection in the complex environment such as undiluted human sweat.Through the experimental comparison,it is concluded that the key factor to enhance the sensing performance of the sensor is lengths of polyethylene glycol molecules,rather than the modification method of the sensor.Meanwhile,a Nafion-based GFET biosensor is developed,which uses the Nafion polymer as an isolated layer.The biosensor is capable of cyclic reconstruction(up to 80 times)with accurate detection of interferon-γ,and enables biomarker detection in undiluted human sweat under mechanical deformations,solving the interference of impurity molecules in human biofluids on sensing signals.A flexible hydrogel aptamer-based graphene field-effect transistor biosensor with adjustable range of detection sensitivity is presented,which overcomes the biofouling of sensor surface with cells and other substances in the blood,as well as low detection limit and large concentration range of biomarkers.Hence,the biosensor achieves the rapid and accurate detection of cardiac troponin ranging from a M to n M in undiluted serum and blood,and the encapsulation of aptamers using hydrogel enhances the stability and durability of the sensor,realizing the long-term storage under room temperature and air environment.The device is also able to stably work after experiencing high temperature environment.It makes the opportunity for flexible aptamer-based graphene field-effect transistor biosensor in practical production and applications.In summary,in view of the theoretical and practical application problems of flexible aptamer-based graphene field-effect transistor biosensor,this work focuses on the wearable or implantable application of flexible biosensor and application of disease biomarker detection,systematically studying the mechanism of the influence of mechanical deformation on the electrical properties and sensing responses of the sensor,which make a theoretical foundation for the subsequent development of flexible sensors.On this basis,a flexible aptamer-based graphene field-effect transistor biosensor that can maintain consistent carrier mobility,transconductance and sensing signal under various mechanical deformations has been developed,and the method of realizing consistent sensing signals in human biofluids and blood environment is explored.The method solves the interference of impurity molecules,blood cells and other substances on the sensing signal,realizing the low detection concentration and large-scale detection of target molecules in a complex environment.At the same time,this work enables A-GFET to realize the ability of multiple reconstruction and improve the stability and durability of the sensor,providing a new approach for the flexible aptamer-based graphene field-effect transistor biosensor in the field of wearable or implantable biomarker detection. |
PDF Full Text Request