The rise of mobile multi-agent robotic platforms is outpacing control paradigms for tasks that require operating in complex, realistic environments. To leverage inertial, energetic, and cost benefits of small-scale robots, critical future applications may depend on coordinating large numbers of agents with minimal onboard sensing and communication resources. In this article, we present the perspective that adaptive and resilient autonomous control of swarms of minimal agents might follow from a direct analogy with the neural circuits of spatial cognition in rodents. We focus on spatial neurons such as place cells found in the hippocampus. Two major emergent hippocampal phenomena, self-stabilizing attractor maps and temporal organization by shared oscillations, reveal theoretical solutions for decentralized self-organization and distributed communication in the brain. We consider that autonomous swarms of minimal agents with low-bandwidth communication are analogous to brain circuits of oscillatory neurons with spike-based propagation of information. The resulting notion of `neural swarm control' has the potential to be scalable, adaptive to dynamic environments, and resilient to communication failures and agent attrition. We illustrate a path toward extending this analogy into multi-agent systems applications and discuss implications for advances in decentralized swarm control.
We examine the potential for low-intensity focused ultrasound to non-invasively produce small (< 1mm3) focal acoustic fields for precise brain stimulation near the skull. Our goal is to utilize transcranial ultrasonic neuromodulation to transform communications and immersive gaming experiences and to optimize neuromodulation applications in medicine. To begin evaluating possible hardware design strategies for engineering ultrasonic brain interfaces, in the present study we evaluated the skull transmission properties of longitudinal and shear waves as a function of incidence angle for 0–2 MHz. We also employed K-wave and time-reversal numerical simulations to further inspect waveform interactions with modeled layers. Timereversal focusing for single-layer and three-layer skull cases were simulated for three different bandwidth ranges (MHz): Broadband(0–2), 1 MHz(0.4–1.4), and 0.2 MHz(0.4–0.6). Broadband and 1 MHz bandwidths emulate the performance of micromachined or piezo membrane ultrasonic arrays, while 0.2 MHz bandwidth is representative of the performance of conventional piezoelectric ultrasonic transducer. We found the 3dB focal volume was ~0.6 mm for broadband and 1 MHz, with the latter showing a slightly larger sidelobe. In contrast, 0.2 MHz nearly doubled the size of the 3dB focal volume while producing prominent sidelobes. Our results provide initial confirmation that a broadband, ultrasonic, linear array can access the first 15 mm of the human brain, which contains circuitry essential to sensory processing including pre-motor and motor planning, somatosensory feedback, and visual attention. These areas are critical targets for providing haptic feedback via non-invasive neural stimulation.
David Blodgett, Eyal Bar-Kochba, Aaron Criss, Tom Criss, Jason Harper, Grace Hwang, Clare Lau, Carissa Rodriguez, Carlos Renjifo, Clara Scholl, Austen Lefebvre, Marek Mirski
Optical neuroimaging technologies aim to observe neural tissue structure and function by detecting changes in optical signals (scatter, absorption, etc…) that accompany a range of anatomical and functional properties of brain tissue. At present, there is a tradeoff between spatial and temporal resolution that is not currently optimized in a single imaging modality. This work focuses on filling the gap between the spatio-temporal resolutions of existing neuroimaging technologies by developing a coherent optics-based imaging system capable of extracting anatomical and functional information across a measurement volume by leveraging a coherent optics-based approach that provides both magnitude and phase information of the sample. We developed a digital holographic imaging (DHI) system capable of detecting these optical signals with a spatial resolution of better than 50 μm over a twenty-five mm2 field of view at sampling rates of 300 Hz and higher. The DHI system operates in the near-infrared (NIR) at 1064 nm, facilitating increased light penetration depths while minimizing contributions from overt changes in oxy- and deoxy-hemoglobin concentration present at shorter NIR wavelengths. This label-free imaging method detects intrinsic signals driven by tissue motion, allowing for innately spatio-temporally registered extraction of anatomical and functional signals in vivo. In this work, we present in vivo results from rat whisker barrel cortex demonstrating signals reflecting anatomical structure and tissue dynamics.
The development of portable non-invasive brain computer interface technologies with higher spatio-temporal resolution has been motivated by the tremendous success seen with implanted devices. This talk will discuss efforts to overcome several major obstacles to viability including approaches that promise to improve spatial and temporal resolution. Optical approaches in particular will be highlighted and the potential benefits of both Blood-Oxygen Level Dependent (BOLD) and Fast Optical Signal (FOS) will be discussed. Early-stage research into the correlations between neural activity and FOS will be explored.
Nanocrescents have become an important surface enhanced Raman scattering (SERS) structure because unlike structures
that rely on a few nanometer gap inter-particle plasmonic coupling to achieve high electrical field, nanocrescents are
fabricated on hundreds of nanometer template sacrificial nanoparticles, where intra-particle plasmonic coupling between
the cavity modes and the tip edges are utilized to achieve high electrical field. Unlike previous efforts, our fabrication
approach creates three dimensional (3-D) up-right oriented nanocrescent structures with controllable cavity rim opening.
Randomly-distributed silica nanoparticles are spun onto a substrate coated with a photoresist layer. Reactive ion etching
is then used to etch into the photoresist to create small narrow pedestal with the nanoparticles serving as etching masks.
The etching recipe and time will determine the diameter of the pedestal and ultimately, the cavity rim opening of the
nanocrescents. We have fabricated and measured nanocrescent structures with as smaller as ~50 nm cavity rim opening.
A maximum enhancement factor ~107 has been achieved so far. Moreover, the repeatability of the enhancement factor
(EF) from one nanocrescent to the next within the same substrate is better than 80%. We attributed the measurement
consistency to the up-right orientation of the nanocrescent structures.
Two-dimensional, large-area, periodic mushroomlike metallodielectric nanostructures have been simulated, fabricated,
and characterized for biosensing applications. Simulations show high electrical field around the tips of the structure. The
fabrication process consists of using holographic lithography to create 2-D periodic nanohole array. Subsequently,
oblique metal deposition on the nanohole array results in mushroomlike nanostructure with a cavity underneath the void
space. The precise geometry of the nanocavity is dependent on the deposition time (thickness). The periodicity of the
array was designed to excite propagating surface plasmon resonance (SPR) modes, while the geometric shape of the
nanostructure excites localized plasmons on its edges. The coupling between these two phenomena results in higher
electric field and thus higher enhancement factor than conventional nanohole array over the whole substrate area ( > 4
cm2). By analyzing the Raman mode of the adsorbed benzenethiol on the surface, the surface enhanced Raman scattering
(SERS) enhancement factor of greater than 106 has been measured. Due to its moderately-high enhancement factor, large-area array, and low-cost fabrication method, this nanostructure can be used for future SERS biosensing applications.
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