Detection of microscopic objects

A method of manufacturing a substrate for use in manufacturing a production master plate for use in manufacturing a detection disc comprising a material having a refractive index of greater than 1.22 and being for carrying samples in an apparatus for detection of microscopic objects in a fluid, the substrate including a first channel and a separate first focus structure, for forming a corresponding detection channel and a corresponding separate second focus structure in the detection disc, the method comprising:

• providing the substrate having a crystallographic silicon structure including crystalline planes;
• etching the first channel into a (100) plane of the crystallographic silicon substrate with an orientation independent of an orientation of the crystalline planes;
• and
• wet etching the first focus structure into the (100) plane of the crystallographic silicon substrate with an orientation aligned with one of the crystalline planes, wherein the first focus structure is a groove having sloping sidewalls, which are aligned with {111} planes of the crystallographic silicon substrate.

A method of manufacturing a detection disc for carrying samples in an apparatus for detection of microscopic objects in a fluid, the method comprising:

• providing a crystallographic silicon substrate;
• etching a first channel into a (100) plane of the crystallographic silicon substrate;
• etching a separate first focus structure into the (100) plane of the crystallographic silicon substrate by wet etching, the first focus structure comprising a groove having sloping {111}-oriented sidewalls, wherein an angle between the (100) plane of the crystallographic silicon substrate and a {111} plane is 54.7°;
• producing a production master plate using the crystallographic silicon substrate;
• and
• injection molding the detection disc using the production master plate, the detection disc including a detection channel and a separate second focus structure, the detection channel having a same geometry as the first channel and the second focus structure having a same geometry as the first focus structure in the crystallographic silicon substrate, and wherein the detection disc comprises a material having a refractive index of greater than 1.22 to give rise to total internal reflection from the sidewalls when a collimated light beam illuminates the sidewalls of the second focus structure from below.