Real-time monitoring of tissue oxygenation within the nervous system is imperative for advancements in neuroscience research and the improvement of clinical diagnostics. Unlike blood oxygenation levels, the partial pressure of oxygen in brain tissue (PbtO2) offers a more direct insight into the localized neural activities and metabolic states. Here, we present a microscale optoelectronic probe for the wireless, real-time monitoring of in vivo partial brain tissue oxygen (PbtO2) levels. This probe measures local PbtO2 concentrations via the luminescent quenching mechanism of phosphorescent dyes. An integrated light-emitting diode (LED) and photodetector are used to generate and capture the optical signals. To facilitate capturing and wirelessly transmitting PbtO2 signals, the device includes miniaturized electronic circuits that can be powered by a battery or an inductive coil. In vitro and in vivo experiments demonstrate the ability to dynamically record oxygen partial pressure (pO2), offering novel exploration opportunities in neuroscience research and clinical applications.
Photon upconversion with the transformation of low-energy photons to high-energy photons is of significant interest for broad applications. Here, we present self-powered, micrometer-scale optoelectronic devices based on III-V materials for high-performance near-infrared to visible upconversion. By taking advantage of its unique photon – “free electron” – photon processes, these thin-film, ultra-miniaturized devices realize fast upconversion that is linearly dependent on incoherent, low-power excitation, with a quantum yield of ~1.5%. By exploiting the advanced manufacturing method, encapsulated, freestanding devices are transferred onto heterogeneous substrates and show desirable biocompatibilities within biological fluids and tissues. These devices as the microscale light sources are implanted in behaving animals, with in vitro and in vivo experiments demonstrating their utility for optogenetic neuromodulation. These results provide routes for high-performance upconversion materials and devices and their unprecedented potential as optical biointerfaces.
Photon upconversion with the transformation of low-energy photons to high-energy photons is of significant interest for broad applications in biomedicine for stimulation, sensing, and imaging. Conventional upconversion materials rely on non-linear light-matter interactions, exhibit incidence dependent efficiencies and require high power excitation. Here, we present self-powered, micrometer-scale optoelectronic devices for high-performance near-infrared (~810 nm) to visible (630 nm red or 590 nm yellow) photon upconversion. Thanks to its unique photon–electron conversion process, these thin-film, ultra-miniaturized devices realize fast upconversion that is linearly dependent on incoherent, low-power excitation, with a quantum yield of ~1.5%. Encapsulated, freestanding devices are transferred onto heterogeneous flexible substrates and show desirable biocompatibilities within biological fluids and tissues. Demonstrations of optogenetic stimulation with upconversion devices as implantable light sources have successfully performed in vitro and in vivo scenarios. 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.
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