Surya Cheemalapati

A real-time classification algorithm for emotion detection using portable EEG

Military personnel, airplane pilots, and bus drivers often operate in stressful conditions when something unexpected can happen and cause dangerous consequences if they do not respond properly. Additionally, stress adversely affects human decision making abilities, therefore prompt, preferably real-time detection of fear is very important. Based on previous studies for non-portable multi-electrode electroencephalography (EEG) systems the ratio of the power of the slow waves to that of the fast waves increases when a person is relaxed and decreases when s/he is scared. In this study we test small portable EEG and develop algorithms for real time detection of the stressful condition - fear. During the experiment we compare EEG signals of subjects in relaxed state with those in stressed state while they are watching a scene from a scary movie. The ratio of the slow/fast wave powers was measured and the observed pattern was similar to one obtained using a multi-electrode system. We integrate stream-processing algorithms in the system to ensure real-time detection of any changes in mental condition and timely generate the alarm event.

Dynamic visualization of photothermal heating by gold nanocages using thermoresponsive elastin like polypeptides.

Understanding how plasmonic nanoparticles collectively generate heat upon exposure to light and thus increase the local temperature of the surrounding medium is critical for many applications such as plasmon-assisted microfluidics, plasmonic tweezers, and photothermal cancer therapy. Reliable temperature manipulation requires the capability to spatially and dynamically analyze local temperature profiles as a function of nanoparticle concentration and laser intensity. In this work, we present a novel method for visualization of local temperature increase using elastin-like polypeptides (ELP). We also propose a robust algorithm that allows the construction of reliable calibration curves using known boundary conditions and Boltzmann sigmoid fit applied to the ELP solutions temperature-absorption transfer function. Using this technique, for the first time, we successfully demonstrated how surface and volume distribution of the nano-heaters affect collective heat generation. This approach allows the visualization of dynamic 2D-temperature profiles and simultaneously enables the measurement of specific temperature at any point in a 2D-map. The experimental setup is compatible with conventional optical microscopy and requires no specialized hardware or complex sample preparation. Finally, the real time visualization of plasmonic heating offers an opportunity to control outcomes of thermo-plasmonics which enables a myriad of practical applications.

Optimization of light delivery by a nanowire-based single cell optical endoscope

Here we present a new design and FDTD simulations of light delivery by a nanowire-based intracellular endoscope. Nanowires can be used for minimally invasive and very local light delivery inside cells. One of the main challenges is coupling of light into the nanowire. We propose a new plasmonic coupler interface between cleaved optical fiber and a nanowire, and optimize light coupling efficiency and contrast.

Design and fabrication of a SAW device with Ta filled microcavities inserted into its delay path for improved power transfer

The authors report the design and fabrication of a surface acoustic wave (SAW) device with improved power transfer due to modification of its delay path. Typically, SAW delay-line devices suffer from relatively high insertion loss (IL) (∼10–30 dB). Our approach is to incorporate an array of microcavities, having square cross-sectional area (λ/2 × λ/2) and filled with tantalum, within the delay path to maximize acoustic confinement to the surface and reduce IL. To determine the effectiveness of the cavities without expending too many resources and to explain trends found in actual devices, a finite element model of a SAW device with tantalum filled cavities having various depths was utilized. For each depth simulated, IL was decreased compared to a standard SAW device. Microcavities 2.5 μm deep filled with tantalum showed the best performance (ΔIL = 17.93 dB). To validate simulated results, the authors fabricated a SAW device on ST 90°-X quartz with microcavities etched into its delay path using deep react...

Plasmono-magnetic material for precise photothermal heating

Noble metal nanoparticles have been extensively studied as photo-sensitive agents for photothermal cancer therapy. Precise control over the size and shape of the nanoparticles allowed strong optical absorption and efficient heat generation necessary for destroying a tumor to be achieved. However, one of the fundamental challenges of application of the nanoparticles towards photothermal cancer therapy is low specificity in the targeting tumor tissue in comparison with the healthy tissue and the resulting unfavorable biodistribution of the nanoparticles. Additional levels of control over particle distribution can be achieved by making the particles magnetic and using external magnets to control their accumulation in a tumor. Since the direct synthesis of particles with a magnetic core and a metallic shell limits the options for design and fine-tuning of plasmonic properties, the alternative approaches to the design of such materials have to be investigated. Here we propose and demonstrate a new design of a hybrid plasmono-magnetic material for photothermal heating created by grafting Au nanocages onto a surface of magnetic micro-beads. Next, we confirm its dual functionality in in vitro studies and show that individual hybrid particles can be magnetically controlled with a precision of a few micrometers and precisely destroy individual cells using plasmonic heating.

mHealth dipstick analyzer for monitoring of pregnancy complications

Dipstick-based urinalysis is routinely used for detection of early signs of such pregnancy complications, as preeclampsia and gestational diabetes. Usually it is done in doctors office using an automatic dipstick analyzer. Here we present a novel smartphone-based colorimeter and demonstrate its application to the measurements of glucose and protein concentrations in biological samples. The key innovations of our approach was to combine powerful image processing encoded into a mobile phone application with a low cost 3D printed sample holder that allowed to control lighting conditions and significantly improved sensitivity. Different solutions with protein and glucose concentrations ranging from 0 to 2000 mg/dL were prepared and analyzed using our system. The smartphone-based colorimeter always correctly classified the corresponding reagent strip pads, what confirms that it can be used as a low cost alternative for commercial dipstick analyzers.

Subcellular and in-vivo Nano-Endoscopy.

Analysis of individual cells at the subcellular level is important for understanding diseases and accelerating drug discovery. Nanoscale endoscopes allow minimally invasive probing of individual cell interiors. Several such instruments have been presented previously, but they are either too complex to fabricate or require sophisticated external detectors because of low signal collection efficiency. Here we present a nanoendoscope that can locally excite fluorescence in labelled cell organelles and collect the emitted signal for spectral analysis. Finite Difference Time Domain (FDTD) simulations have shown that with an optimized nanoendoscope taper profile, the light emission and collection was localized within ~100 nm. This allows signal detection to be used for nano-photonic sensing of the proximity of fluorophores. Upon insertion into the individual organelles of living cells, the nanoendoscope was fabricated and resultant fluorescent signals collected. This included the signal collection from the nucleus of Acridine orange labelled human fibroblast cells, the nucleus of Hoechst stained live liver cells and the mitochondria of MitoTracker Red labelled MDA-MB-231 cells. The endoscope was also inserted into a live organism, the yellow fluorescent protein producing nematode Caenorhabditis elegans, and a fluorescent signal was collected. To our knowledge this is the first demonstration of in vivo, local fluorescence signal collection on the sub-organelle level.

Real Time Fear Detection Using Wearable Single Channel Electroencephalogram

Real time detection of emotional state has multiple applications for security, safety and identification of dangerous situations. Traditionally electroencephalogram (EEG) based emotion studies are conducted in controlled lab environment with multi-channel systems and large signal processing power. In order to be useful in real world situation the system for emotion detection has to be miniature, portable and working in real time supported by calculations that can be provided by a processor power of a mobile phone. Here we present our results on real time fear detection using portable single electrode EEG system conducted on 10 subjects. We studied possibility of translation of the markers previously identified for complex multi-electrode system - ratios of slow waves to fast waves into real time portable system. It was demonstrated using Student’s t-test that the average value of the monitored parameter during normal state was significantly higher than that of during a scary stimulus with a P value of (0.027) ~ 0.03 for Theta/ Beta. The framework for portable fear detection together with the markers discussed in this study can enable many applications important for the soldiers in the battlefield or police officers while being under attack as an indicator that help is urgently needed.