1：Experimental Design and Method Selection:

The study involved designing a 3D-printed rack and pinion focussing mechanism for a ball lens-based microscope. The design was created using AutoDesk 123D Design and printed using an Ultimaker 2.0+ printer. The mechanism was tested for focus stability using an edge-based contrast measure.

2：0+ printer. The mechanism was tested for focus stability using an edge-based contrast measure. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples included onion skin cells stained with Safranin, a thin smear of blood stained with Giemsa, and Plasmodium infected blood. Images were acquired using a cellphone camera and a research-grade microscope for comparison.

3：List of Experimental Equipment and Materials:

Equipment included a 3D printer (Ultimaker 2.0+), a Zeiss Axio Imager Z.1 microscope, and an LG G3 Smartphone. Materials included poly-lactic acid for printing, ball lenses, and various stains for sample preparation.

4：0+), a Zeiss Axio Imager Z.1 microscope, and an LG G3 Smartphone. Materials included poly-lactic acid for printing, ball lenses, and various stains for sample preparation. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The 3D-printed focussing mechanism was assembled and integrated with a paper microscope. Time-series images of samples were acquired to test focus stability. The edge-based contrast measure was used to quantify focus.

5：Data Analysis Methods:

Images were processed using ImageJ macros, and data were analyzed using Python and MATLAB scripts. The focus measure was calculated based on edge information in the images.