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.
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.
Transparent magnesium aluminate spinel ceramics were additively manufactured via a laser direct deposition method in this study. With a minimum porosity of 0.3% achieved, highly transparent spinel samples with the highest total optical transmittance of 82% at a wavelength of 632.8 nm, were obtained by a 3D printing approach. However, cracking was found to be a major issue affecting printed spinel samples. To control prevalent cracking, the effect of silica dopants was investigated. Increased silica dopants reduced average total crack length by up to 79% and average crack density by up to 71%. However, a high dopant level limited optical transmission, attributed to increased porosity and formation of secondary phase. Further investigation found that with decreased average fracture toughness, from 2.4 MPa·m1/2 to 1.9 MPa·m1/2, the obvious reduction in crack formation after doping was related to decreased grain size and introduction of softer secondary phase during deposition. The study demonstrated the feasibility of the proposed laser direct deposition method in directly fabricating transparent spinel ceramics while dopants showed potentials in addressing cracking issues.
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