Hardware, Volume 4, Issue 2 (June 2026) – 4 articles

Organic waste management remains a pressing environmental and economic challenge, particularly in small-scale or domestic contexts where access to industrial composting technologies is limited. This study investigates the performance of the BSG-2 fermenter, a low-cost aerobic system designed to convert brewery spent grain (BSG) and vegetable waste into nutrient-rich compost through solid-state fermentation. The fermenter, constructed from food-grade plastic, relied on intermittent forced aeration, and manual temperature and pH control to sustain microbial activity. Temperature, pH, and substrate degradation were monitored throughout a complete fermentation cycle. The system achieved consistent bio-thermal performance with peak temperatures of approximately 32 °C and a substrate volume reduction of 30–40%, confirming active microbial metabolism and substantial organic matter degradation. Minimal odor generation and low energy input highlighted the fermenter’s environmental suitability. While occasional anaerobic pockets and limited heat retention were observed, these limitations could be addressed through improved insulation and automated aeration. The sustained mesophilic heat generation observed in the system may also present opportunities for low-grade thermal recovery in small-scale applications, such as localized environmental conditioning, although the magnitude of heat produced is limited. Overall, the BSG-2 fermenter demonstrates a feasible, replicable approach to valorizing organic waste into compost and sustained mesophilic heat generation using simple, accessible materials, contributing to circular economy strategies and sustainable small-scale waste management. Full article

In autologous microtia reconstruction, achieving optimal skin adherence to the cartilage framework is critical for aesthetic success. This study validates a novel, low-cost closed suction system assembled from a 20 mL syringe, a 5 mL syringe barrel acting as a rigid internal lock, and a fenestrated butterfly cannula. In a prospective cohort of 100 consecutive cases, the system effectively coapted the skin flap in all patients without major complications. Clinical data revealed a mean drainage duration of 6 days and 19 h (95% CI: 6 d 11 h to 7 d 4 h) and a mean collected fluid volume of 17.36 mL (95% CI: 16.77–17.95 mL). Blinded expert evaluation using the weighted 13-point Sharma scale demonstrated “Excellent” framework definition in 81.7% of patients. This system offers exceptional reliability and disruptive cost-efficiency, achieving stable vacuum pressure at a production cost of approximately 0.60 USD. These findings provide a compelling proof-of-concept for an accessible, high-performance alternative in auricular reconstruction, establishing a robust foundation for broader clinical adoption and future comparative validation in resource-limited surgical settings. Full article

Lab-on-a-chip devices offer high efficiency, low volume and fast analytical measurement, but their use is still niche. A key component for these devices is the detector, and one common type of detection is fluorescence spectroscopy. However, in some cases the detector can be bulky and lose the appeal of small-footprint devices. To make lab-on-a-chip devices truly compact, detectors must also be compact. In this paper we discuss the use of simple and low-cost commercial multispectral sensors for use in lab-on-a-chip devices, more specifically for fluorescence detection, which we demonstrate to allow detection on nanomolar scale with a simple experimental setup. Full article

Supercritical carbon dioxide (sCO₂) is characterized by low viscosity and a peak in specific heat capacity near the pseudo-critical point, making it a promising coolant for microelectronics. However, most existing sCO₂ test rigs are designed for large-scale thermodynamic cycle studies and lack the capability for controlled, localized heat transfer measurements in small channels. This work presents CO₂-SASS (Scientific Assessment of heat transfer in the Supercritical State), a modular, high-pressure test rig designed to measure local heat transfer coefficients and pressure drops in stainless-steel tubes with diameters on the order of 1–3 mm. The system provides independent control of pressure, mass flow and heating, with direct local wall and fluid temperature as well as precise absolute and differential pressure measurements. Particular emphasis is placed on high-accuracy temperature acquisition, including individual thermocouple calibration and cold-junction bias correction. A detailed uncertainty analysis highlights the dominant role of temperature measurement accuracy, especially for small wall–fluid temperature differences near the pseudo-critical point. Full article