Abstract
Moldless lens manufacturing techniques using standard droplet dispensing technology often require precise control over pressure to initiate fluid flow and control droplet formation. We have determined a series of interfacial fluid parameters optimised using standard 3D printed tools to extract, dispense and capture a single silicone droplet that is then cured to obtain high quality lenses. The dispensing process relies on the recapitulation of liquid dripping action (Rayleigh-Plateau instability) and the capturing method uses the interplay of gravitational force, capillary forces and liquid pinning to control the droplet shape. The key advantage of the passive lens fabrication approach is rapid scale-up using 3D printing by avoiding complex dispensing tools. We characterise the quality of the lenses fabricated using the passive approach by measuring wavefront aberration and high resolution imaging. The fabricated lenses are then integrated into a portable imaging system; a wearable thimble imaging device with a detachable camera housing, that is constructed for field imaging. This paper provides the full exposition of steps, from lens fabrication to imaging platform, necessary to construct a standalone high resolution imaging system. The simplicity of our methodology can be implemented using a regular desktop 3D printer and commercially available digital imaging systems.
Highlights
Moldless lens manufacturing techniques using standard droplet dispensing technology often require precise control over pressure to initiate fluid flow and control droplet formation
Decentralisation of complex scientific instruments by leveraging on consumer electronics and mobile devices[1], i.e. laptops, smartphones, mobile smart devices, is becoming useful in a variety of applications ranging from point-of-care medicine[2], geophysics research[3,4], education[5] and nature conservation[6]
The combination of digital imaging with new computational tools[9], biomarkers[10] and 3D printing[11] have ushered in practical in-vivo imaging screening on mobile devices[12,13,14] for primary care and low resources settings. This is especially useful in image-intensive medical practices; ophthalmology, dermatology and pathology, where the accurate characterisation of samples at macroscopic and microscopic level is crucial for identification of diseases
Summary
Droplet formation is ubiquitous in many facets of droplet dispensing technology where a flowing stream of fluid filament collapses into smaller masses of fluid drops[20]. The lenses cured shows a thick base due to increased capillary force (shown in Supplementary Information S4) To this end, we showed that the appropriate combination of the cone angle, lens holder distance and holder design greatly affects how the convexity of silicone droplets can be passively held in position. We showed that the appropriate combination of the cone angle, lens holder distance and holder design greatly affects how the convexity of silicone droplets can be passively held in position This marks a significant advancement of the passive dispenser approach over previously published works is the high throughput process by using basic tools that can be 3D printed, the quality of this form of lenses needs to be further verified. The optical properties of the silicone lenses are carefully characterised with a wavefront sensor (Shack-Hartmann wavefront sensor) and an optical surface profiler (white light interferometer)
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