There is strong medical demand for continuous CO2 partial pressure (pCO2) monitoring. While there has been significant progress in the development of CO2 sensors, their implementation with optical wearable device remains under-explored. We have developed highly sensitive, rapidly responding, humidity insensitive and photostable CO2 sensing materials that can be used with optical wireless wearable device for real-time monitoring pCO2. The preliminary results reveal the prototype device is able to reliably detect reversible CO2 changes within physiological ranges.
We present the creation of wearable devices that measure transcutaneous partial oxygen or carbon dioxide pressure (tcpO2 or tcpCO2) non-invasively. The devices are highly sensitive to the physiological pO2/pCO2, and detects changes in luminescence (lifetime or ratiometric brightness) of mellaporphyrins or HPTS dye molecules embedded within breathable, hydrophobic films. Our first in human measurements reveal the devices are able to detect quick and subtle changes in tcpO2 due to local and systemic changes in blood flow of skin or deeper muscle tissue. Models to extract tissue oxygenation and oxygen consumption rate are explored.
An oxygen-sensing microneedle array (MNA) was developed to monitor oxygen partial pressure in tissue in a minimally invasive fashion. The working principle is based on the quenching of emission intensity and phosphorescence lifetime of a Pt-core porphyrin embedded into the MNA. It was shown that the MNA is sufficiently robust to puncture human skin and to detect changes in oxygenation within the physiologically relevant range of 0-160 mmHg. Moreover, it was demonstrated that the MNA can be implemented into a wearable wireless optical readout system rendering the MNA a novel and user-friendly technique to monitor oxygen partial pressure in tissue.
Non-invasive approaches to human data collection have become relevant in athlete performance monitoring and the clinical setting. Historically, these metrics rely on measurements such as blood or tissue oxygen saturation, yet saturation lacks a degree of specificity clinicians and professional trainers desire. To overcome this, we developed a wearable, non-invasive, optical transcutaneous tissue oxygenation sensor that overcomes inefficiencies in specific measurements and the devices that collect those measurements. We report on innovations to the prototype device, including the implementation of more sophisticated quantification methods directly on the device as well as the addition of new sensors to measure other clinical parameters.
We present a wireless, wearable device to measure transcutaneous partial oxygen pressure (tcpO2) non-invasively. The device, tuned to physiological range pO2, detects changes in phosphorescence lifetime and intensity of ultra-bright metalloporphyrins embedded within breathable films. We have implemented machine learning algorithms to improve the accuracy of the measurements against changes in temperature, photobleaching, inter-device/film variations, etc. Our first in human measurements reveal the devices are able to detect quick and subtle changes in tcpO2 due to local and systemic changes in blood flow of skin or deeper muscle tissue. Models to extract tissue oxygenation and oxygen consumption rate are explored.
We have developed different portable tools based on phosphorescence lifetime and intensity measurements to be used together with syringes, needles, and catheters to measure oxygen partial pressure deep inside tissue with the aim to improve the assessment of acute compartment syndrome (ACS). Due to their portability and universality, the tools will also be useful in other hypoxia-related conditions such as vascular diseases, diabetic wounds, cancer, and traumatic injuries. We will present designs as well as results from in vivo porcine model studies.
Wearable devices have found widespread application in recent years as consumer electronics for sports and health tracking. A metric of health which is overlooked in currently available technology is the measurement of oxygen in living tissue, a key component in the cellular energy production. We report on the development of an optical wireless wearable prototype for transcutaneous oxygen monitoring based on the phosphorescence emission of a highly breathable oxygen sensing film. The device is truly wearable, weighs under 20 grams,is completely self-contained, requires no external readout electronics and is highly sensitive to oxygen in the physiological range.
There is an unmet need for simple-to-use oximetry devices that can map tissue oxygenation over large areas while being easily integrated into clinical standard-of-care workflows. We present a phosphorescence-based approach which features red-emitting porphyrin molecule constructs, embedded within a paint-on hydrogel bandage for tissue oxygen concentration imaging. The bandage emission is visible by eye which enables oxygen imaging even in the presence of skin autofluorescence. Preclinical testing to validate correlations between bandage oxygenation maps and perfusion is ongoing, and by allowing gelation to occur on the skin the bandage can conform to odd topologies, such as ears.
The possible influence of internal barrier dynamics on spin, charge transport and their fluctuations in organic spintronics remains poorly understood. Here we present investigation of the electron transport and low frequency noise at temperatures down to 0.3K in magnetic tunnel junctions with an organic PTCDA barriers with thickness up to 5 nm in the tunneling regime and with 200 nm thick Alq3 barrier in the hopping regime. We observed high tunneling magneto-resistance at low temperatures (15-40%) and spin dependent super-poissonian shot noise in organic magnetic tunnel junctions (OMTJs) with PTCDA. The Fano factor exceeds 1.5-2 values which could be caused by interfacial states controlled by spin dependent bunching in the tunneling events through the molecules.1 The bias dependence of the low frequency noise in OMTJs with PTCDA barriers which includes both 1/f and random telegraph noise activated at specific biases will also be discussed. On the other hand, the organic junctions with ferromagnetic electrodes and thick Alq3 barriers present sub-poissonian shot noise which depends on the temperature, indicative of variable range hopping.
The time dependent transient lateral photovoltaic effect (T-LPE) has been studied with microsecond time resolution and with chopping frequencies in the kHz range, in lithographically patterned 21 nm thick, 5, 10 and 20 micron wide and 1500 micron long Co lines grown over naturally passivated p-type Si (100). We have observed a nearly linear dependence of the LPE transient response with the laser spot position. An unusual T-LPE dynamic response with a sign change in the laser-off stage has also been corroborated by numerical simulations. A qualitative explanation suggests a modification of the drift-diffusion model by including the influence of a local inductance. In addition, influence of anisotropic magnetoresistance of the Co line structure on dynamic response on T-LPE has been investigated. Specifically, we have experimentally investigated influence of the direction of the external magnetic field respect to the drift velocity of the photogenerated carriers on the T-LPE. We have observed notable dependence of the T-LPE on the magnetic field in the small field range (below 100 Oe), compatible with anisotropic magnetoresistance values. The strong influence of the magnetization alignment on the dynamic response of photogenerated carriers has been also observed through a phase sensitive lock-in experiment. These findings indicate that the microstructuring of the ferromagnetic line based position sensitive detectors (PSD) could improve their space-time resolution and add capability of magnetic field tuning of the main PSD characteristics.
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