Abstract
In this work, a sensor to evaluate sterilization processes with hydrogen peroxide vapor has been characterized. Experimental, analytical and numerical methods were applied to evaluate and study the sensor behavior. The sensor set-up is based on planar interdigitated electrodes. The interdigitated electrode structure consists of 614 electrode fingers spanning over a total sensing area of 20 mm2. Sensor measurements were conducted with and without microbiological spores as well as after an industrial sterilization protocol. The measurements were verified using an analytical expression based on a first-order elliptical integral. A model based on the finite element method with periodic boundary conditions in two dimensions was developed and utilized to validate the experimental findings.
Highlights
Sterilization processes are important in various industrial fields such as pharmaceutics, medicine and food packaging
Analysis of the interdigitated electrode (IDE) structure with atomic force microscopy (AFM) depicts uneven electrode edges, which are related to the lift-off process and the mechanical stability of the thin structures (Figure 8)
In addition to the error due to geometric uncertainty, air humidity, temperature and material purity have an effect on the capacitance measurements in contrast to the ideal conditions of the numerical model
Summary
Sterilization processes are important in various industrial fields such as pharmaceutics, medicine and food packaging. In food packaging industry various sterilization processes are used and the applied method depends on the object to be sterilized. Pre-formed food packages are guided through the sterilization chamber of the aseptic filling machine. The standard methods to evaluate the sterilization process effectiveness are microbiological challenge tests (end-point or count-reduction tests) [5,6]. For these methods the surfaces of multiple test packages are inoculated with a refined sample of a resilient microorganism. Spores of Bacillus atrophaeus (B. atrophaeus) are applied as an indicator microorganism to evaluate H2O2 vapor sterilization processes. The sensor validation was achieved by developing a representative numerical model based on the finite element method (FEM)
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