This paper discusses the possible use of 3D fused deposition modeling (FDM) to fabricate capillaries for low-cost chemiresistive gas sensors that are often used in various applications. The disadvantage of these sensors is low selectivity, but 3D printed FDM capillaries have the potential to increase their selectivity. Capillaries with 1, 2 and 3 tiers with a length of 1.5 m, 3.1 m and 4.7 m were designed and manufactured. Food and goods available in the general trade network were used as samples (alcohol, seafood, chicken thigh meat, acetone-free nail polish remover and gas from a gas lighter) were also tested. The “Vodka” sample was used as a standard for determining the effect of capillary parameters on the output signal of the MiCS6814 sensor. The results show the shift of individual parts of the signal in time depending on the parameters of the capillary and the carrier air flow. A three-tier capillary was chosen for the comparison of gas samples with each other. The graphs show the differences between individual samples, not only in the height of the output signal but also in its time characteristic. The tested 3D printed FDM capillaries thus made it possible to characterize the output response by also using an inexpensive chemiresistive gas sensor in the time domain.

The objective of this study was to evaluate the effect of citrus fiber (1% wt/wt) on the physicochemical, rheological, textural, tribological, and sensory properties of quark cheese spreads with different fat content (10%, 15%, and 20% wt/wt). Physicochemical properties, including pH, DM, and water activity, were not affected by citrus fiber addition. Furthermore, rheological and textural analyses showed that citrus fiber increased samples' hardness and viscoelastic moduli, probably by reinforcing the protein-polysaccharide matrix, especially in low-fat variants. Tribological measurements indicated that higher fat improved lubrication, whereas fiber-containing quark cheese spread samples exhibited slightly higher coefficients of friction due to increased structural rigidity. Additionally, color analysis revealed minor shifts toward darker and more yellow tones when citrus fiber was used. Moreover, sensory evaluation confirmed that citrus fiber addition did not affect most of the tested organoleptic attributes, with slight improvement in flavor. The findings indicate that incorporating citrus fiber into quark cheese spreads can improve their functional properties, facilitate fat reduction, and promote the sustainable utilization of byproducts in dairy products.

Inexpensive chemiresistive sensors are often insufficiently selective as they are sensitive to multiple components of the gas mixture at the same time. One solution would be to insert a device in front of the sensor that separates the measured gas mixture and possibly isolates the unwanted components. This study focused on the fabrication and characterization of a compact unit, which was fabricated by 3D printing, for the separation and detection of simple gas mixtures. The capillary, the basic part of the compact unit, was 4.689 m long and had a diameter of 0.7 mm. The compact unit also contained a mixing chamber on the inlet side and a measuring chamber with a MiCS-6814 sensor on the outlet side. Mixtures of ethanol and water at different concentrations were chosen for characterization. The measured calibration curve was found to have a reliability of R² = 0.9941. The study further addressed the elements of environmental friendliness of the materials used and their sustainability.