The degradation of the perovskite solar cell structure was expected recently to be reversible, which opened a new gate to the enhancement of the device lifetime by reversing the process. However, the kinetic details of the structural collapse and recovery are still missing, without which the perovskite reversibility cannot be further explored. Due to the experimental difficulty, a purposeful numerical model was conducted in this report, to simulate the water diffusion process in the perovskite structure in both directions. It was found that the moisture diffusion needs to be initiated by a certain level of structural imperfection and is non-Fickian, as assisted by the collapse of the perovskite into the 1D chains. The reversibility was verified by the back diffusion, but accompanied by hysteresis, stagnancy, and even surprising instability, which initiated the water flow under initial equilibrium, due possibly to the imbalance during the reconstruction of the perovskite lattice. These observations offer new insights to form strategies of improvement, for example, via the possible self-healing perovskite devices.

Projection imaging has been employed widely in many areas, such as x-ray radiography, due to its penetration power and ballistic geometry of their paths. However, its resolution limit remains a major challenge, caused by the conflict of source intensity and source size associated with image blurriness. A simple yet robust scheme has been proposed here to solve the problem. An unconventional square aperture, rather than the usual circular beam, is constructed, which allows for the straightforward deciphering of a blurred spot, to unravel hundreds originally hidden pixels. With numerical verification and experimental demonstration, our proposal is expected to benefit multiple disciplines, not limited to x-ray imaging.

The global battle against the Covid-19 pandemic relies strongly on the human defence of antibody, which is assumed to bind the antigen’s Receptor Binding Domain with its Hypervariable Region. Due to the similarity to other viruses such as SARS, however, our understanding of the antibody-virus interaction has been largely limited to the genomic sequencing, which poses serious challenges to the containment, vaccine exploration and rapid serum testing. Based on the physical/chemical nature of the interaction, infrared spectroscopy was employed to reveal the binding disparity, when unusual temperature dependence was discovered from the 1550cm-1 absorption band, attributed to the hydrogen bonds by carboxyl/amino groups, binding the SARS-CoV-2 spike protein and closely resembled SARS-CoV-2 or SARS-CoV-1 antibodies. The infrared absorption intensity, associated with the number of hydrogen bonds, was found to increase sharply between 27°C and 31°C, with the relative absorbance matches at 37°C the hydrogen bonding numbers of the two antibody types (19 vs 12). Meanwhile the ratio of bonds at 27°C, calculated by thermodynamic exponentials rather than by the layman’s guess, produces at least 5% inaccuracy. As a result, the specificity of the SARS-CoV-2 antibody will be more conclusive beyond 31°C, instead of at the usual room temperature of 20°C - 25°C, when the vaccine research and antibody diagnosis would likely be undermined. Beyond genomic sequencing, the temperature dependence, as well as the bond number match at 37°C between relative absorbance and the hydrogen bonding numbers of the two antibody types, are not only of clinical significance in particular, but also of a sample for the physical/chemical understanding of the vaccine-antibody interactions in general.

The global battle against the COVID-19 pandemic relies strongly on the human defense of antibody, which is assumed to bind the antigen’s receptor binding domain (RBD) with its hypervariable region (HVR). Due to the similarity to other viruses such as SARS, however, our understanding of the antibody-virus interaction has been largely limited to the genomic sequencing, which poses serious challenges to containment and rapid serum testing. Based on the physical/chemical nature of the interaction, infrared spectroscopy was employed to reveal the binding disparity, the real cause of the antibody-virus specificity at the molecular level, which is inconceivable to be investigated otherwise. Temperature dependence was discovered in the absorption value from the 1550 cm−1 absorption band, attributed to the hydrogen bonds by carboxyl/amino groups, binding the SARS-CoV-2 spike protein and closely resembled SARS-CoV-2 or SARS-CoV-1 antibodies. The infrared absorption intensity, associated with the number of hydrogen bonds, was found to increase sharply between 27 °C and 31 °C, with the relative absorbance matching the hydrogen bonding numbers of the two antibody types (19 vs. 12) at 37 °C. Meanwhile, the ratio of bonds at 27 °C, calculated by thermodynamic exponentials, produces at least 5% inaccuracy. Beyond genomic sequencing, the temperature dependence, as well as the bond number match at 37 °C between relative absorbance and the hydrogen bonding numbers of the two antibody types, is not only of clinical significance in particular but also as a sample for the physical/chemical understanding of vaccine–antibody interactions in general.