The static Coulomb potential of Quantum Electrodynamics (QED) is calculated in the presence of a strong magnetic field in the lowest Landau level (LLL) approximation using two different methods. First, the vacuum expectation value of the corresponding Wilson loop is calculated perturbatively in two different regimes of dynamical mass m dyn. , i.e., |q 2 | ≪ m 2 dyn. ≪ |eB| and m 2 dyn. ≪ |q 2 | ≪ |eB|, where q is the longitudinal components of the momentum relative to the external magnetic field B. The result is then compared with the static potential arising from Born approximation. Both results coincide. Although the arising potentials show different behavior in the aforementioned regimes, a novel dependence on the angle θ between the particle-antiparticle's axis and the direction of the magnetic field is observed. In the regime |q 2 | ≪ m 2 dyn. ≪ |eB|, for strong enough magnetic field and depending on the angle θ, a qualitative change occurs in the Coulomb-like potential; Whereas for θ = 0, π the potential is repulsive, it exhibits a minimum for angles θ ∈]0, π[.

Polymerase chain reaction (PCR) is a powerful tool for nucleic acid amplification and quantification. However, long thermocycling time is a major limitation of the commercial PCR devices in the point-of-care (POC). Herein, we have developed a rapid droplet-based photonic PCR (dpPCR) system, including a gold (Au) nanofilm-based microfluidic chip and a plasmonic photothermal cycler. The chip is fabricated by adding mineral oil to uncured polydimethylsiloxane (PDMS) to suppress droplet evaporation in PDMS microfluidic chips during PCR thermocycling. A PDMS to gold bonding technique using a double-sided adhesive tape is applied to enhance the bonding strength between the oil-added PDMS and the gold nanofilm. Moreover, the gold nanofilm excited by two light-emitting diodes (LEDs) from the top and bottom sides of the chip provides fast heating of the PCR sample to 230 °C within 100 s. Such a design enables 30 thermal cycles from 60 to 95 °C within 13 min with the average heating and cooling rates of 7.37 ± 0.27 °C/s and 1.91 ± 0.03 °C/s, respectively. The experimental results demonstrate successful PCR amplification of the alcohol oxidase (AOX) gene using the rapid plasmonic photothermal cycler and exhibit the great performance of the microfluidic chip for droplet-based PCR.