This work focuses on the design and characterization of a system for measuring and calibration of liquid micro-flows down to 5 nL min−1. The experimental setup relies on a telecentric imaging system mounted on a high-precision, computer controlled linear stage to track a moving liquid meniscus in a glass capillary. The position of the linear stage can be automatically adjusted to track the motion of the liquid front over distances of up to 15 cm. All fluidic components were placed inside a temperature regulated chamber at 36.0 ± 1.1 °C with a maximum variability ΔT = ± 0.1 °C for time intervals shorter than 1 h. The combined flow-rate uncertainty has been evaluated for measurement times from 15 s to 1 h and nominal flow rates between 5 and 50 nL min−1. At 5 nL min−1, an extended flow-rate uncertainty better that 8.3% can be attained for measurement times equal to or longer than 60 s. The uncertainty approaches asymptotically 5.4% for measurement times longer than 300 s or flow rates higher than 50 nL min−1.
This work presents the improvements of an experimental setup for measuring ultra-low flow rates down to 5 nl/min. The system uses a telecentric CCD imaging system mounted on a high-precision, computer-controlled linear stage to track a moving liquid meniscus inside a glass capillary. Compared to the original setup, the lowest attainable expanded uncertainty at any flow rate has been reduced from 5.4% to 2%. In addition, the conformity with specification of three commercial micro-fluidic devices was evaluated using the new setup: one syringe pump, one implantable infusion pump and one thermal flow sensor. The flow sensor and the implantable infusion pump met the compliance criteria (coverage probability 95%). The syringe pump however, failed to meet the specifications at 5 nl/min and 10 nl/min. No assessment could be made at higher flow rates.
The nursing of patients with wounds is an essential part of medical healthcare. In this context, cold atmospheric-pressure plasma sources can be applied for skin decontamination and stimulation of wound healing. One of these plasma devices is the commercially available kINPen® MED (neoplas tools GmbH), a cold atmospheric-pressure plasma jet which is approved as a medical device, class-IIa. For the plasma treatment, a sterile disposable spacer is recommended to ensure a constant and effective distance between plasma and skin. The disadvantage of this spacer is its form and size which means that the effective axis/area is not visible for the attending doctor or qualified personnel and consequently it is a more or less intuitive treatment. In addition, the suggested perpendicular treatment is not applicable for the attending specialist due to lack of space or patient/wound positioning. A concept of a sensory unit was developed to measure the treatment distance and to visualize the effective treatment area for different angles. To determine the effective area for the plasma treatment, some exemplary methods were performed. Thus, the antimicrobial (Staphylococcus aureus DSM799/ATCC6538) efficacy, reactive oxygen species (ROS) distribution and (vacuum) ultraviolet ((V)UV) irradiation were determined depending on the treatment angle. Finally, a simplified first approach to visualize the effective treatment area at an optimal distance was designed and constructed to train attending specialists for optimal wound area coverage.
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