The integration of particle counters within lab-on-chip (LOC) microfluidic devices creates a range of valuable tools for healthcare such as cell counting, and synthesis applications e.g. materials fabrication. Avoidance of long and/ or complex fabrication processes can aid the uptake of these devices, specially within resource-poor societies. We present an additively manufactured microfluidic particle counter. The device features a hydrodynamic focusing chamber to stream the particles past embedded optical fibres for their detection. The intensity of occluded light through the fibre was found to be related to the size of the particles, allowing particles of different sizes to be identified. The signal-to-noise ratio and reproducibility of the particle analysis was optimised to three objectives (pulse magnitude, uniformity and periodicity) via the use of a genetic algorithm (GA). Once optimised the device was able to count particles upto 5.5 × 10 4 particles ml -1 , and size particles in a mixture.
Resistive Pulse Sensors, RPS, provide detailed characterisation of materials from the nanoparticle up to large biological cells on a particle-to-particle basis. During the RPS experiment, particles pass through a channel or pore which conduct ions, and the change in ionic current versus time is monitored. The change in current during each translocation, also known as a 'pulse', is dependent upon the ratio of the particle and channel dimensions. Here we present a facile and rapid method for producing Flow-RPS sensors which do not require lithographic processes. The Additively Manufactured, AM, sensor has channel dimensions that can be easily controlled. In addition, the fabrication process allows the sensor to be quickly assembled, disassembled, cleaned and reused. Further, the RPS sensor can be created with a direct interface for fluidic pumps or imaging window for complimentary optical microscopy. We present experiments and simulations of the RPS sensor, showing how the pulse shape are dependent upon the channel morphology and how the device can count and size particles across a range of flow rates and ionic strengths. The use of pressure-driven fluid flow through the device allowed a rapid characterisation of particles down to concentrations as low as 1 × 10 -3 particles per ml which equated to one event per second.
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