Microscale optoelectronic infrared-to-visible upconversion devices and their use as injectable light sources

Abstract

Optical upconversion that converts infrared light into visible light is of significant interest for broad applications in biomedicine, imaging, and displays. Conventional upconversion materials rely on nonlinear light-matter interactions, exhibit incidence-dependent efficiencies, and require high-power excitation. We report an infrared-to-visible upconversion strategy based on fully integrated microscale optoelectronic devices. These thin-film, ultraminiaturized devices realize near-infrared (∼810 nm) to visible [630 nm (red) or 590 nm (yellow)] upconversion that is linearly dependent on incoherent, low-power excitation, with a quantum yield of ∼1.5%. Additional features of this upconversion design include broadband absorption, wide-emission spectral tunability, and fast dynamics. Encapsulated, freestanding devices are transferred onto heterogeneous substrates and show desirable biocompatibilities within biological fluids and tissues. These microscale devices are implanted in behaving animals, with in vitro and in vivo experiments demonstrating their utility for optogenetic neuromodulation. This approach provides a versatile route to achieve upconversion throughout the entire visible spectral range at lower power and higher efficiency than has previously been possible.

Expanding the Toolbox of Upconversion Nanoparticles for In Vivo Optogenetics and Neuromodulation

“…These obstacles have been partially overcome by the advent of wireless and implantable optogenetic stimulators 35b,37. A recent design based on microscale optoelectronic implants allows NIR upconversion to take place directly on an array implanted into the brain . The encapsulation of the implants with biocompatible surfaces led to an enhanced local field potential for an in vivo optogenetic mice model upon excitation at 810 nm.…”

Recent Advances in Flexible Inorganic Light Emitting Diodes: From Materials Design to Integrated Optoelectronic Platforms

“…The result is a broad collection of injectable optogenetic platforms with tether‐free operation, on freely moving animals (Figure c) capable of use in conventional scenarios as well as those (e.g., social experiments) where conventional fiber or head‐mounted systems would result in parasitic, confounding challenges. [13j,k] Besides powering schemes that use resonant inductive coupling, recent work highlights a “self‐powered,” ultracompact (typical size ≈220 µm × 220 µm) light source that integrates photovoltaic diode layers and LED layers, monolithically in the same device stack (9 µm thick) . Here, the photovoltaic unit captures external, low‐energy IR photons (≈810 nm) and provides photogenerated currents and voltages capable of driving LEDs with higher‐energy, visible emission (630 or 590 nm), thus enabling IR‐to‐visible upconversion in an engineered material structure with a practical quantum yield over 1%.…”

Single-cell micro- and nano-photonic technologies

“…Wang, Lin, Chen, et al packaged UCNPs in a glass micro-electrode and, in combination with a robotic laser projection system, achieved behavioural conditioning in freely-moving animals by modulating neural activity in various brain regions [63]. An alternative upconversion approach, proposed by Ding et al [64], relies instead on the realization of self-powered microscale devices through the combination of GaAs photovoltaic diodes (PDs) and AlGaInP-based light emitting diodes (LEDs); a thin (9µm) implantable probe for stimulating nerve cells in the mouse primary somatosensory cortex via NIR-to-visible conversion (~810nm to ~630nm) was obtained. Even though the single photodetectors/light source couple is quite large (220µm ´ 220µm) if compared to neurons size, preliminary exploration to scale down the device to an area of 10µm ´ 10µm was made [64].…”