Fel0500

The optoelectronic devices were laminated on a large photodiode (S170C, Thorlabs) and covered with a custom-built reflective piece. The captured light power was measured using an optical power meter (PM100D, Thorlabs). For measurements involving micro-LEDs covered with phosphor-PDMS composite, the converted light (λ = 590 or 620 nm) and the transmitted blue light (λ = 470 nm) powers were quantified individually using optical filters with cut-off λ = 500 nm (FES0500, FEL0500, Thorlabs).

Benchtop microscopic imaging was accomplished by placing the cell capture interface (layer 2) on a glass slide and imaged using a 10X objective and a filter cube for blue bandpass filter excitation and green long-pass filter emission. Nikon TS100 fluorescence microscope (Tokyo, Japan) was used for imaging.
Smartphone-based microscopic imaging was accomplished using a smartphone (iPhone 8; Apple Inc., Cupertino, CA, USA) connected to a commercially available microscope attachment (XFox Professional 300X Optical Glass Lenses; X&Y Ind., Shenzhen, China), attached to a 500 nm long-pass optical filter (FEL0500, Thorlabs Inc., Newton, NJ, USA). Again, smartphone imaging was also accomplished by sandwiching the WBC capture interface between the optical filter and a transparent glass surface. During detection the WBC capture interface is illuminated using a 466 nm LED (TLHB5100; Vishay, Malvern, PA, USA) powered by a 9 V battery. The current is limited using a 500 Ω resistor.