Treatment of neurological anomalies, whether done invasively or not, places stringent demands on device functionality and size. We have developed a micro-spectrometer for use as an implantable neural probe to monitor neuro-chemistry in synapses. The micro-spectrometer, based on a NASA-invented miniature Fresnel grating, is capable of differentiating the emission spectra from various brain tissues. The micro-spectrometer meets the size requirements, and is able to probe the neuro-chemistry and suppression voltage typically associated with a neural anomaly. This neural probe-pin device (PPD) is equipped with wireless power technology (WPT) to enable operation in a continuous manner without requiring an implanted battery. The implanted neural PPD, together with a neural electronics interface and WPT, enable real-time measurement and control/feedback for remediation of neural anomalies. The design and performance of the combined PPD/WPT device for monitoring dopamine in a rat brain will be presented to demonstrate the current level of development. Future work on this device will involve the addition of an embedded expert system capable of performing semi-autonomous management of neural functions through a routine of sensing, processing, and control.
Development of an optical neurotransmitter sensing device using nano-plasmonic probes and a micro-spectrometer for real time monitoring of neural signals in the brain is underway. Clinical application of this device technology is to provide autonomous closed-loop feedback control to a deep brain stimulation (DBS) system and enhance the accuracy and efficacy of DBS treatment. By far, we have developed an implantable probe-pin device based on localized field enhancement of surface plasmonic resonance on a nanostructured sensing domain which can amplify neurochemical signals from evoked neural activity in the brain. In this paper, we will introduce the details of design and sensing performance of a proto-typed microspectrometer and nanostructured probing devices for real time measurement of neurotransmitter concentrations.
Microwave/RF energy has been used for wireless power transmission including many therapeutic applications, such as transurethral microwave therapy (TUMT). For safe uses of RF power, it is important to know how to deliver microwave energy on focused area and control the temperature changes not to drastically increase on adjacent areas. Graphical analysis of thermal loading factor is important to understand how to achieve effective transmission of microwave through the tissue. The loss mechanism while transmission often appears as thermal effects due to absorption of microwave, especially for materials such as human skin, muscles, and other organic parts including brain. In this paper, microwave thermal effects are investigated to measure temperatures, penetration depth through animal skins in terms of input power and various frequencies.
This result will be compare with the case of human applications.
A miniaturized solid-state optical spectrometer chip was designed with a linear gradient-gap Fresnel
grating which was mounted perpendicularly to a sensor array surface and simulated for its performance
and functionality. Unlike common spectrometers which are based on Fraunhoffer diffraction with a
regular periodic line grating, the new linear gradient grating Fresnel spectrometer chip can be
miniaturized to a much smaller form-factor into the Fresnel regime exceeding the limit of conventional
spectrometers. This mathematical calculation shows that building a tiny motionless multi-pixel microspectrometer
chip which is smaller than 1mm3 of optical path volume is possible. The new Fresnel
spectrometer chip is proportional to the energy scale (hc/λ), while the conventional spectrometers are
proportional to the wavelength scale (λ). We report the theoretical optical working principle and new data
collection algorithm of the new Fresnel spectrometer to build a compact integrated optical chip.
New medical device technology is essential for diagnosing, monitoring, and curing wide
spectrum of diseases, anomalies and inflictions. For neural applications, currently available
devices are generally limited to either a curing or a probing function. In this paper we review the
technology requirements for new neural probe and cure device technology currently under
development. The concept of probe-pin device that integrates the probes for neurochemistry,
neuroelectricity, temperature and pressure into a single embodiment with a wireless power
transmission was designed for the purpose of deep brain feedback stimulation (DBFS) with
insitu neural monitoring. The probe considered for monitoring neurochemistry is a
microspectrometer. The feature and size of micro-spectrometer are defined for the DBFS device.
Two types of wireless power transmission technology were studied for DBFS device operation.
The test results of pig skin showed that both power transmission technologies demonstrated the
feasibility of power feed through human tissue.
Most of today's spectrometers are based on Fraunhofer diffraction with a periodic regular line grating.
We demonstrate a new type of a spectrometer which is based on Fresnel diffraction that can be
miniaturized smaller than Fraunhofer diffraction limit, a2/λ where a is the aperture size, and λ is the
wavelength of the light. The theory, fabrication, and optical performance of the miniaturized Fresnel
spectrometer with a circular Fresnel grating, i.e. zone-plate will be presented. The theoretical calculation
shows that the spectral resolution of Fresnel spectrometer is not fundamentally determined by the size
of the grating but it is determined by the total number of rings. The miniaturized Fresnel spectrometer
has a circular grating of 750 micrometer diameter and the volume of the optical path between the
grating and the aperture slit is only 1mm3. In spite of this small dimension, it achieved a spectral
resolution of 22nm which is similar to the typical value of a color filter.
A versatile optical characterization system is fabricated to measure various optical properties of
materials and devices. The optical system is based on Michelson interferometer with advanced software
algorithm to measure the intensity, phase angle, polarization state, and coherence of transmitted or
reflected light from the materials and devices under test. Innovative contour map of phase/intensity vs.
time/physical-quantity relation shows the dynamic evolution of interference patterns of multiple points
in the analysis area. Advanced software semi-automatically calculates change of photon intensity, phase
angle, polarization, and coherence which are results of various applied physical quantities such as
voltage, electric field, current, temperature, pressure, chemical density, and reaction time. The
measured optical property changes are converted by software to the changes of intrinsic and extrinsic
properties of materials and devices under test. The system is designed for multi-point measurements
which are suitable for 2D-array-pixel type devices. Therefore, this versatile optical measurement system
can accelerate the development of advanced adaptive optics elements and phase control elements.
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