An MXene–graphene field-effect transistor (FET) sensor for both influenza virus and 2019-nCoV sensing was developed and characterized. The developed sensor combines the high chemical sensitivity of MXene and the continuity of large-area high-quality graphene to form an ultra-sensitive virus-sensing transduction material (VSTM). Through polymer linking, we are able to utilize antibody–antigen binding to achieve electrochemical signal transduction when viruses are deposited onto the VSTM surface. The MXene–graphene VSTM was integrated into a microfluidic channel that can directly receive viruses in solution. The developed sensor was tested with various concentrations of antigens from two viruses: inactivated influenza A (H1N1) HA virus ranging from 125 to 250,000 copies/mL and a recombinant 2019-nCoV spike protein ranging from 1 fg/mL to 10 pg/mL. The average response time was about ∼50 ms, which is significantly faster than the existing real-time reverse transcription-polymerase chain reaction method (>3 h). The low limit of detection (125 copies/mL for the influenza virus and 1 fg/mL for the recombinant 2019-nCoV spike protein) has demonstrated the sensitivity of the MXene–graphene VSTM on the FET platform to virus sensing. Especially, the high signal-to-viral load ratio (∼10% change in source-drain current and gate voltage) also demonstrates the ultra-sensitivity of the developed MXene–graphene FET sensor. In addition, the specificity of the sensor was also demonstrated by depositing the inactivated influenza A (H1N1) HA virus and the recombinant 2019-nCoV spike protein onto microfluidic channels with opposite antibodies, producing signal differences that are about 10 times lower. Thus, we have successfully fabricated a relatively low-cost, ultrasensitive, fast-responding, and specific inactivated influenza A (H1N1) and 2019-nCoV sensor with the MXene–graphene VSTM.

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Structural battery composites are capable of significant system level mass and volume reductions not possible with separate battery and structural components by simultaneously carrying mechanical loads and storing electrical energy. The ability to 3D print lithium-ion structural batteries in arbitrary geometries would not only allow a flexible battery design but also facilitate its implementation as a structural component. This study presents a new 3D carbon fiber structural battery composite 3D printed by an ultraviolet (UV)-assisted coextrusion deposition method. With individual carbon fibers coated by solid polymer electrolyte (SPE) and dispersed within cathode doped matrix, energy storage is achieved in micro-battery cells at the fiber level within the 3D printed structural battery composite. The 3D printed structural battery composites with various complex geometries are demonstrated by successfully powering up LEDs. The SPE coating and cathode doping effect on microstructure, printability, mechanical and electrochemical properties are further characterized and investigated. A trade-off between printability and electrochemical performance is observed due to hindered curing by the doped cathode materials. The obtained electrochemical and mechanical performance is comparable to the carbon fiber based structural battery composites fabricated by conventional lay-up processes. These well demonstrate the great potentials of the proposed 3D printing method in rapidly fabricating functional structural battery composite components with complex geometries.