Pen Plotter as a Low-Cost Platform for Rapid Device Prototyping with Solution-Processable Nanomaterials

The use of inexpensive benchtop plotters in combination with refillable writing pens and markers as a powerful route to print nanomaterial-based inks on paper substrates is studied. It is proved that this approach is very robust, it can be used to print inks of many different solution-processable nanomaterials, and is very precise, allowing pattern features with pitch separation as narrow as 80 μm. The general character of this printing platform by printing van der Waals materials, organic semiconductors, hybrid perovskites and colloidal nanoparticles with a broad range of properties (from insulators to superconductors) is illustrated. The system is used to easily create several example applications such as an all-printed, paper-supported photodetector. This printing platform can be very helpful for research groups with a wealth of expertise in synthesis of solution-processable nanomaterials but that lack the infrastructure, resources, and expertise to perform traditional inkjet printing for fast device prototyping.     

Two chemical engineers look at the COVID-19 pandemic

Chemical engineering involves a skill set that is transferrable to a broad range of other areas. A case in point is the work that is being done by chemical engineers to better understand and fight the COVID-19 epidemic. In this study, we consider a problem that has eluded the COVID-19 research community, which is nevertheless very tractable with a chemical engineering mindset: the true or intrinsic mortality rate of COVID-19, that is, the fraction or percentage of COVID-19-infected people that die of the disease. We solve this problem in two locations (Spain and the state of New York) for the epidemic's first wave using a combination of daily death data, a fit of a computer simulation of an epidemiological model with adjustable parameters, and independent results of immunological blood testing on a random sample of the population. Parallels are drawn with the problem of determining the turnover frequency of a catalyst based on a similar combination of data and approaches. It is concluded from the study that the intrinsic mortality rate of COVID-19 was 1.45 ± 0.45% during the first wave, a number that reflects OECD countries. By incorporating data on the age dependence of the mortality rate, a relationship f_mort = (3.0 ± 0.7) × 10⁻⁵ exp(0.1a), where a is the age in years, is tentatively put forward for the mortality rate as a fraction.