The inspiration came from a combination of the Lobster's superposition compound eyes and the retinal structure of the small elephantnose fish, the later featuring thousands of crystalline cups covering its inner retina.
In a paper titled "Artificial eye for scotopic vision with bioinspired all-optical photosensitivity enhancer", the researchers unveil an optical lens made out of thousands of micro-photocollectors (μ-PCs), each consisting of a tiny glass pillar with parabolic reflective sidewalls that focus the faint incoming light through a tiny output port.
The micro-photocollectors are arranged on a dome-shaped structure, so as to mimic the lobster's superposition compound eye where multiple light input ports concentrate the incoming light onto individual sensor pixels.
Using this unique lens, the researchers reported a four-fold improvement in light sensitivity when imaging objects in what could be described as pitch-black darkness.
To manufacture the minuscule parabolic side-walled μ-PCs only about 120μm tall, the engineers relied on a hybrid laser ablation process.
"First, we use laser ablation to form the parabolic micro-cup structures in glass. Then we smoothen the sidewall surface by reflowing Su-8 photoresist, followed by coating aluminium as the reflective (mirror) layer", explained Hongrui Jiang, professor of electrical and computer and biomedical engineering at UW–Madison and the corresponding author on the study.
These micro-cups are then transferred to a 300μm thick PDMS hemispheric membrane to create the so-called bioinspired photosensitivity enhancer (BPE), in effect a fish-lens which can be used to boost just any imaging system, regardless of the imaging sensors in use.