Lateral flow test engineering and lessons learned from COVID-19

The acceptability and feasibility of large-scale testing with lateral flow tests (LFTs) for clinical and public health purposes has been demonstrated during the COVID-19 pandemic. LFTs can detect analytes in a variety of samples, providing a rapid read-out, which allows self-testing and decentralized diagnosis. In this Review, we examine the changing LFT landscape with a focus on lessons learned from COVID-19. We discuss the implications of LFTs for decentralized testing of infectious diseases, including diseases of epidemic potential, the ‘silent pandemic’ of antimicrobial resistance, and other acute and chronic infections. Bioengineering approaches will play a key part in increasing the sensitivity and specificity of LFTs, improving sample preparation, incorporating nucleic acid amplification and detection, and enabling multiplexing, digital connection and green manufacturing, with the aim of creating the next generation of high-accuracy, easy-to-use, affordable and digitally connected LFTs. We conclude with recommendations, including the building of a global network of LFT research and development hubs to facilitate and strengthen future diagnostic resilience

Evaluating Graphene as a Channel Material in Spintronic Logic Devices

University of Minnesota Ph.D. dissertation. 2016. Major: Electrical Engineering. Advisor: Steven Koester. 1 computer file (PDF); 201 pages.Spintronics, a class of devices that exploit the spin properties of electrons in addition to the charge properties, promises the possibility for nonvolatile logic and memory devices that operate at low power. Graphene is a material in which the spin orientation of electrons can be conserved over a long distance, which makes it an attractive channel material in spintronics devices. In this dissertation, the properties of graphene that are interesting for spintronics applications are explored. A robust fabrication process is described for graphene spin valves using Al2O3 tunnel tunnel barriers and Co ferromagnetic contacts.  Spin transport was characterized in both few-layer exfoliated and single-layer graphene, and spin diffusion lengths and spin relaxation times were extracted using the nonlocal spin valve geometry and Hanle measurements. The effect of input-output asymmetry on the spin transport was investigated.  The effect of an applied drift electric field on spin transport was investigated and the spin diffusion length was found to be tunable by a factor of ~8X (suppressed to 1.6 µm and enhanced to 13 µm from the intrinsic length of 4.6 µm using electric field of ±1800 V/cm). A mechanism to induce asymmetry without excess power dissipation is also described which utilizes a double buried-gate structure to tune the Fermi levels on the input and output sides of a graphene spin logic device independently. It was found that different spin scattering mechanisms were at play in the two halves of a small graphene strip. This suggests that the spin properties of graphene are strongly affected by its local environment, e.g. impurities, surface topography, defects. Finally, two-dimensional materials beyond graphene have been explored as spin channels.  One such material is phosphorene, which has low spin-orbit coupling and high mobility, and the interface properties of ferromagnets (cobalt and permalloy) with this material were explored.  This work could potentially enable spin injection without the need for a physical tunnel barrier to solve the conductivity mismatch problem inherent to graphene

Imaging stray magnetic fields using 3D scanning techniques

A new versatile magnetic field scanning system has been developed; based on a Micromagnetics® STJ-020 tunnelling magneto-resistance (TMR) sensor and a 3-axis positioning arm, with a 3D-printed sensor enclosure, precision goniometer and integrated microscopic sight. Calibration of the hardware, quantifying the slack/backlash of the three axes, and the capabilities of the system and its sensors are recounted. The system is capable of; scanning precisely and repeatably at 1 μm/step with a 4 x 2 μm2 sensing area; scanning smooth continuously dynamic magnetic field changes at a sampling frequency up to 1 MHz; producing scans of three-dimensional volumes; and resolving the "eld components along multiple axes. The Scanner Control so7ware (available as open access†) has been developed to be modular, powerful and adaptable, permi9ng large datasets from multiple sensors to be analysed. Studies are made of the domain structure in 3% Grain-Oriented Electrical Steel, Amorphous Alloy materials, Cubexdoubly oriented Si-Fe Alloy and manufactured Planar coils, both statically and when reacting dynamically to externally applied alternating fields. Interpretation of the resulting field maps and comparison of the advantages and disadvantages of the Scanner system over other domain observation methods is given. The ability to scan a three-dimensional volume above the surface of the sample and to derive the Hz and Hx components from only a single axis sensor is developed and demonstrated, both statically and dynamically. The principles are tested against the known geometries of constructed planar coils, the expected fields from which are determined using Finite Element Modelling.The novel developments of the project, and the advantages of the developed Scanner System, culminate in, and are ultimately demonstrated by, the "nal dynamic three-dimensional, component-resolved stray-"eld scan of a volume above the surface of an unprepared sample of coated 3% grain-oriented electrical steel under alternating applied magnetic field

Contactless Measurement of Magnetic Nanoparticles on Lateral Flow Strips Using Tunneling Magnetoresistance (TMR) Sensors in Differential Configuration

Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning prototype based on tunneling magnetoresistance (TMR) sensors for quantification of MNPs present in lateral flow strips (LFSs). The sensing unit of the prototype composes of two active TMR elements, which are parallel and closely arranged to form a differential sensing configuration in a perpendicular magnetic field. Geometrical parameters of the configuration are optimized according to theoretical analysis of the stray magnetic field produced by the test line (T-line) while strips being scanned. A brief description of our prototype and the sample preparation is presented. Experimental results show that the prototype exhibits the performance of high sensitivity and strong anti-interference ability. Meanwhile, the detection speed has been improved compared with existing similar techniques. The proposed prototype demonstrates a good sensitivity for detecting samples containing human chorionic gonadotropin (hCG) at a concentration of 25 mIU/mL. The T-line produced by the sample with low concentration is almost beyond the visual limit and produces a maximum stray magnetic field some 0.247 mOe at the sensor in the x direction

Contactless Measurement of Magnetic Nanoparticles on Lateral Flow Strips Using Tunneling Magnetoresistance (TMR) Sensors in Differential Configuration

Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning prototype based on tunneling magnetoresistance (TMR) sensors for quantification of MNPs present in lateral flow strips (LFSs). The sensing unit of the prototype composes of two active TMR elements, which are parallel and closely arranged to form a differential sensing configuration in a perpendicular magnetic field. Geometrical parameters of the configuration are optimized according to theoretical analysis of the stray magnetic field produced by the test line (T-line) while strips being scanned. A brief description of our prototype and the sample preparation is presented. Experimental results show that the prototype exhibits the performance of high sensitivity and strong anti-interference ability. Meanwhile, the detection speed has been improved compared with existing similar techniques. The proposed prototype demonstrates a good sensitivity for detecting samples containing human chorionic gonadotropin (hCG) at a concentration of 25 mIU/mL. The T-line produced by the sample with low concentration is almost beyond the visual limit and produces a maximum stray magnetic field some 0.247 mOe at the sensor in the x direction