![]() If there are other people around in the same room they should be wearing protections too. Wear protective glasses adapted the wavelength. Extreme care must be taken to prevent the beam from being viewed directly or through reflections. You may need to adapt some parts depending on your hardware (type of Arduino board, here for a RichUno, type of laser.).ĭirect viewing of laser diode emission may cause eye damage. The image below shows the parts of the device. Project implementation - Let's get started! ![]() Portability - The device will be built around an Arduino board connected to a PC via a USB port, sending intensity time series.Cost - Affordable components and 3d printed case.Usability - Simple to measure a sample.The laser is turned off if the case is incidentally opened. Safety - The case fully encloses the system.Then other types of colloidal systems such as bovine milk and milk substitutes will be investigated. Well-characterized high molecular weight proteins (spectrin) and fibres (cellulose) in solution will be studied in the first instance. However, the aim of this project is to explore the technical boundaries of the DLS technique with accessible components, at the cost of longer measurement time, limited accuracy and reduced particle size range. Also, small particles move faster in solution, requiring high frequency signal sampling (up to 100 kHz). This is critical for the smallest particles (a few nanometers) which tend to scatter the fewer light. The light collected at large angle from a transparent solution is really dim, so modern DLS equipments use expensive components such as high intensity lasers and single photon detectors to enhance their signal to noise ratio and enable an accurate measurement within minutes. Since particles in solutions undergo Brownian motion, this collected intensity varies with time and then size can be deconvoluted from the intensity time series. Photons coming from different particles interfere in the detector to yield a specific intensity. The scattered light is collected at a specific angle from the beam (here 90°). More broadly, we hope that this approach will also contribute to future projects involving light scattering or high frequency data logging.ĭynamic Light Scattering works as follows (see figure below): a laser beam is shone onto the sample and is scattered to all directions by the particles (particles dimensions are assumed to be smaller than the laser wavelength). On the contrary, this project aims at exploring DLS principles and boundaries with low-cost components and open-source design. Some recent equipment can even determine the shape of non-spherical particles! Typical commercial DLS equipments are expensive (typically over 40k£) because of the use of high quality lasers and detectors, allowing measurements over a broad range of particle sizes and concentrations. In DLS, particles size is back-calculated from the way light scattered from a laser beam evolves with time as particles undergo Brownian motion in the fluid. In particular, Dynamic Light Scattering (DLS) is widely used for dilute particles suspensions. For submicron particles however, more advanced and expensive techniques have to be employed such as electron microscopy or light scattering. For particles larger than about a micron, optical microscopy can be used in conjunction with image analysis softwares. You are advised to read the comments for more updates.Ĭharacterising the size of micro and nano-particles is important in many applications such as protein aggregation and complex fluids studies. Edit: Please note that this is still a work in progress, and it seems that some results were obtained by shear luck (as it happens in research).
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