Mechanical Engineering Challenges in Building a High Performance Hematology Auto-Scanner

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Shonit™ is a smart hematology analyser powered by advancements in artificial intelligence, image processing and cloud computing. One of the critical components of the solution is the smart scanner which enables to digitise the data efficiently for the AI models on the cloud. Today, I am going to talk about challenges involved in achieving the accuracy and precision from a mechanical engineering perspective.

The imaging of blood samples involves focusing on objects which vary in sizes from 0.5 microns (platelets) to 20 microns (WBCs). For the blood samples spread on a slide, the surface variations on the glass cause the blood cells to go out of the focus from the objective lens while moving from one Field of View (FOV) to another. To get back into focus the slide must be brought closer or farther from the objective lens with a precision in the range 100 to 500 nanometres. Achieving such high precision and accuracy to commanded values is a multidisciplinary challenge being addressed in the robotics team at SigTuple.

From a mechanical engineering perspective, a lot of consideration in design, selection of components, materials and manufacturing processes are required to achieve the desired precision. First would be the selection of actuating mechanisms, wherein the system should have least backlash to ensure the repeatability across the movements, a rigid mechanism which have less wear and tear and an easily serviceable mechanism to fit in the economics as well. The selection of material also plays a vital role here. The material for the scanner should provide adequate strength to all the dynamic parts to withstand the vibrations, acceleration, deceleration and does not degrade over the period and has good chemical resistance to any medical grade chemicals. The overall design is also done in a way to eliminate cantilever type structures to as much extent as possible to reduce bending and vibrations. Even after getting the selection of components and materials right, the assembly of the individual components plays a crucial role here and directly affects the image quality captured from the optics. The assembly operation of a dynamic system itself requires a lot of intermediate testing of alignments and fitments to make sure that the component spacing, and movements are inside the tolerance region and will not affect the movement post assembly.

One of the major challenges that we faced was to stabilize vibrations occurring in the slide movement at a micron level, which is clearly visible as a motion blur in the image quality while capturing them.Second challenge was to achieve the high accuracy in relative flatness and parallelism of optics with respect to the critical components. To improve on these factors we emphasised mainly on the machining processes with high accuracy and precision, our quality testing methods for assembly checks and some software tweaks to accommodate for the same. The next set of challenge for us now will be to ensure the repeatability throughout the new assemblies and to make the system more efficient by developing the existing system to increase the efficiency of system.

In Shonit™ there is still a long way to go in design and development as far as mechanical design and development is concerned. I hope you like this blog and In my next blog, I will be explaining more about the technicalities of the small imperfections which play a critical role in the overall output delivery and about a new technology in CAD  which is a powerful and helpful tool for performing hundreds of design iterations in a short amount of time.

 

 

Image Credits: Metlflo.com, tes.com, equipoferrer.com