Modeling, design and experimental characterization of Micro-Electro-Mechanical-Systems for gas chromatographic applications

Design parameters, process flows, electro-thermal-fluidic simulations and experimental characterizations of Micro-Electro-Mechanical-Systems (MEMS) suited for gas-chromatographic (GC) applications are presented and thoroughly described in this thesis, whose topic belongs to the research activities the Institute for Microelectronics and Microsystems (IMM)-Bologna is involved since several years, i.e. the development of micro-systems for chemical analysis, based on silicon micro-machining techniques and able to perform analysis of complex gaseous mixtures, especially in the field of environmental monitoring. In this regard, attention has been focused on the development of micro-fabricated devices to be employed in a portable mini-GC system for the analysis of aromatic Volatile Organic Compounds (VOC) like Benzene, Toluene, Ethyl-benzene and Xylene (BTEX), i.e. chemical compounds which can significantly affect environment and human health because of their demonstrated carcinogenicity (benzene) or toxicity (toluene, xylene) even at parts per billion (ppb) concentrations. The most significant results achieved through the laboratory functional characterization of the mini-GC system have been reported, together with in-field analysis results carried out in a station of the Bologna air monitoring network and compared with those provided by a commercial GC system. The development of more advanced prototypes of micro-fabricated devices specifically suited for FAST-GC have been also presented (silicon capillary columns, Ultra-Low-Power (ULP) Metal OXide (MOX) sensor, Thermal Conductivity Detector (TCD)), together with the technological processes for their fabrication. The experimentally demonstrated very high sensitivity of ULP-MOX sensors to VOCs, coupled with the extremely low power consumption, makes the developed ULP-MOX sensor the most performing metal oxide sensor reported up to now in literature, while preliminary test results proved that the developed silicon capillary columns are capable of performances comparable to those of the best fused silica capillary columns. Finally, the development and the validation of a coupled electro-thermal Finite Element Model suited for both steady-state and transient analysis of the micro-devices has been described, and subsequently implemented with a fluidic part to investigate devices behaviour in presence of a gas flowing with certain volumetric flow rates.

Innovative strategies for the mitigation of acrylamide content in different food products

Acrylamide (AA) is an undesirable food toxic compound, classified as 'probably carcinogenic to humans' by the International Agency for Research on Cancer due to its toxic effects, including neurotoxicity, genotoxicity, carcinogenicity and reproductive toxicity. AA is mainly formed during the heat treatment of foods (> 120 °C) by the Maillard reaction, an essential reaction that also allows the desired levels of shelf-life and sensory properties of various food products to be achieved. Over the years, authorities and regulations have become more restrictive regarding the maximum levels of AA permitted in foods and beverages. The latest Commission Regulation (EU) 2017/2158 contains reference levels and measures to reduce AA in several food groups that contribute to the highest dietary intake, making necessary the study of promising AA mitigation strategies. The aim of this PhD research project was to identify, characterise and optimise some AA mitigation strategies in the most at-risk widely consumed foods such as potato, coffee and bakery products. Some AA control strategies were selected and investigated for each food category, also considering the main quality characteristics of the final products. The comprehensive results obtained during the three years of research activity have allowed a deeper knowledge of the traditional and innovative AA mitigation strategies, which can be extremely useful for both the food industry and international authorities. The most promising strategies studied in terms of reduction of AA while maintaining the main quality characteristics of the examined foods were: the application of pulsed electric fields and yeast immersion as pre-treatments of chips for frying; the selection of high roasting degrees for coffee products; the selection of static baking conditions for biscuits; the optimisation of alternative biscuit’ formulations by both the use of chickpea legume flour and of flour from bean with intact cotyledon cell walls.