Flexible, Replaceable, Low-cost Sampling and Storage Integrated System
Our aim is to develop a microfluidic system with the integration of different elements (microvalves, microfilters etc). The fabrication of a Lab-on-a-Chip is a challenge for rapid prototyping in one step and our ambition is to produce low-cost flexible sensing devices that are compact for multiple detection of ATS.
Since the “miniaturized total analysis system” (μTAS) concept was presented by Manz et al. in 1990, it has been established that the properties of microfluidic or lab-on-a-chip (LoC) systems make them highly suitable for the fabrication of compact, miniaturized analytical devices for a variety of large applications in different fields, including: environmental monitoring, food, and biomedical analysis. Cleary et al tested a first generation in-situ phosphate analyser at a wastewater treatment plant. The sample inlet was modified with a membrane filter holder for contact with a membrane filter (Supor membrane filter, 0.4 µm pore size with a 25 mm diameter). The sample was drawn through the membrane, into the analyser system using a solenoid pump, and then transported to the microfluidic chip. Over days 18-21 of the trial, the membrane filter became clogged with solids. After the filter was replaced, a close agreement in the data was resumed, and the membrane filter was changed at weekly intervals to prevent a recurrence of clogging.
Due to the inherent issues of working within harsh conditions and medium, we propose the waste water intake will consist of a filtering system positioned at the beginning of the microchannel. Here, the system will be designed in such a way as to reduce clogging with solids. In this instance, a cross flow filter or a membrane filter based on a porous thermoplastic film will be incorporated, respectively. The sample will then be drawn through the microchannel and to the sensors using capillary forces and aided by the design of the microfluidic system. If a positive measurement is observed, the waste water will be stored in one of the multiple in-built tanks. Here, microvalves will be integrated at the entrance for each tank for the storage of the waste water. If the measurement is negative, the waste water will be removed through the waste outlet.
Sensor element integration will be achieved using specific alignment positions to chemically bond the sensor to the polymeric microfluidic system. This is standard practice for the fabrication of lab-on-a-chip (LoC) devices. Development of the sensors based on thermoplastic films can be covalently bonded and form a strong chemical adhesion to polymeric microfluidic systems.In recent years, a huge interest has developed into replicating the techniques of PDMS microfluidic structures onto polymer membranes for bioanalytical analysis due to the versatility of the polymeric material. This is advantageous due to the fact that polymers are less expensive, flexible (attachment to the robot form), and fabrication is far easier in comparison with Si-based substrates and thus costs of such a device are reduced. In addition, polymer technology is seen as the ultimate solution to the corrosion problem in waste water applications, but more work will be necessary to realize microfluidic networks in chemically durable materials such as polyetheretherketone (PEEK).