S. Abdollah Mirbozorgi

Towards a kinect-based behavior recognition and analysis system for small animals

This paper presents a Microsoft Kinect®-based image processing system that is capable of automated tracking and behavior recognition in freely moving animals. The depth image provided by the Kinect infrared (IR) camera is used in the image processing algorithm, which works under both bright and dark conditions, compared to conventional red-green-blue (RGB) cameras that need proper lighting or LEDs on the headstage. For animal tracking, the subject trajectory was recorded/refreshed every 0.5 s, with a maximum positioning error of 1.6 cm. For behavior recognition, 5 different types of rodent behavior were considered: standstill, walking, grooming, rearing, and rotating are classified using a support vector machine (SVM) with radial basis function kernels. The algorithm was verified in vivo using data acquired from a 2 month-old Sprague Dawley rat weighting ~400 grams in a standard homecage and compared with manual ground truth. The overall behavior recognition accuracy was 95.34% and 89.41% in bright and dark conditions, respectively.

Robust Wireless Power Transmission to mm-Sized Free-Floating Distributed Implants

This paper presents an inductive link for wireless power transmission (WPT) to mm-sized free-floating implants (FFIs) distributed in a large three-dimensional space in the neural tissue that is insensitive to the exact location of the receiver (Rx). The proposed structure utilizes a high-Q resonator on the target wirelessly powered plane that encompasses randomly positioned multiple FFIs, all powered by a large external transmitter (Tx). Based on resonant WPT fundamentals, we have devised a detailed method for optimization of the FFIs and explored design strategies and safety concerns, such as coil segmentation and specific absorption rate limits using realistic finite element simulation models in HFSS including head tissue layers, respectively. We have built several FFI prototypes to conduct accurate measurements and to characterize the performance of the proposed WPT method. Measurement results on 1-mm receivers operating at 60 MHz show power transfer efficiency and power delivered to the load at 2.4% and 1.3 mW, respectively, within 14–18 mm of Tx–Rx separation and 7 cm2 of brain surface.

Toward a distributed free-floating wireless implantable neural recording system

To understand the complex correlations between neural networks across different regions in the brain and their functions at high spatiotemporal resolution, a tool is needed for obtaining long-term single unit activity (SUA) across the entire brain area. The concept and preliminary design of a distributed free-floating wireless implantable neural recording (FF-WINeR) system are presented, which can enabling SUA acquisition by dispersedly implanting tens to hundreds of untethered 1 mm3 neural recording probes, floating with the brain and operating wirelessly across the cortical surface. For powering FF-WINeR probes, a 3-coil link with an intermediate high-Q resonator provides a minimum S21 of -22.22 dB (in the body medium) and -21.23 dB (in air) at 2.8 cm coil separation, which translates to 0.76%/759 μW and 0.6%/604 μW of power transfer efficiency (PTE) / power delivered to a 9 kΩ load (PDL), in body and air, respectively. A mock-up FF-WINeR is implemented to explore microassembly method of the 1×1 mm2 micromachined silicon die with a bonding wire-wound coil and a tungsten micro-wire electrode. Circuit design methods to fit the active circuitry in only 0.96 mm2 of die area in a 130 nm standard CMOS process, and satisfy the strict power and performance requirements (in simulations) are discussed.

Optimal design of a 3-coil inductive link for millimeter-sized biomedical implants

For wireless power transfer to multiple millimeter-sized implantable medical devices (IMDs), power delivered to a load should be over minimum operating power of the IMDs and power transfer efficiency (PTE) should be maximized to reduce specific absorption rate across a wide area of interest. We have demonstrated advantages of using a 3-coil inductive link to energize multiple IMDs and its PTE optimization to power up bonding-wire wound coils implanted in tissue environment, in contrast to earlier works that focused on 2-coil inductive link optimization methodologies to a single mm-sized IMD. HFSS simulation results show superiority of the 3-coil inductive link to wirelessly deliver power to multiple mm-sized coils. A 3-coil inductive link optimization method, considering the desired radius of the resonator coil, is presented. Measured PTE to the boding-wire wound coil in tissue media were 9.13% and 2.01% at 275 MHz and 131 MHz when resonator radii were 0.5 cm and 1 cm, respectively.

A wirelessly-powered homecage with animal behavior analysis and closed-loop power control

This paper presents a new EnerCage-homecage system, EnerCage-HC2, for longitudinal electrophysiology data acquisition experiments on small freely moving animal subjects, such as rodents. EnerCage-HC2 is equipped with multi-coil wireless power transmission (WPT), closed-loop power control, bidirectional data communication via Bluetooth Low Energy (BLE), and Microsoft Kinect® based animal behavior tracking and analysis. The EnerCage-HC2 achieves a homogeneous power transfer efficiency (PTE) of 14% on average, with ~42 mW power delivered to the load (PDL) at a nominal height of 7 cm by the closed-loop power control mechanism. The Microsoft Kinect® behavioral analysis algorithm can not only track the animal position in real-time but also classify 5 different types of rodent behaviors: standstill, walking, grooming, rearing, and rotating. A proof-of-concept in vivo experiment was conducted on two awake freely behaving rats while successfully operating a one-channel stimulator and generating an ethogram.

A closed-loop wireless homecage for optogenetic stimulation experiments

This paper presents a smart EnerCage-homecage (HC) system for optogenetic stimulation, equipped with magnetic resonance based wireless power transmission (WPT), closed-loop power control, and data communication via Bluetooth Low Energy (BLE). The proposed system is encompassed with four rectangular slanted overlapping high-Q resonators and a wire-wound driver coil, all tuned at 13.56 MHz. An optical headstage is implemented capable of driving 4 micro light-emitting diodes (μ-LEDs) based on stimulation commands received via the BLE link on-the-fly, while being wirelessly powered in a closed-loop fashion. Measurements show that the entire headstage unit was provided with up to 51 mW throughout the homecage up to the maximum elevation of 10 cm, while the transmitter (Tx) power consumption changed from 1.5 W to 2.1 W (overall η, 2.4-3.4%).

Position and Orientation Insensitive Wireless Power Transmission for EnerCage-Homecage System

We have developed a new headstage architecture as part of a smart experimental arena, known as the EnerCage-HC2 system, which automatically delivers stimulation and collects behavioral data over extended periods with minimal small animal subject handling or personnel intervention in a standard rodent homecage. Equipped with a four-coil inductive link, the EnerCage-HC2 system wirelessly powers the receiver (Rx) headstage, irrespective of the subjects location or head orientation, eliminating the need for tethering or carrying bulky batteries. On the transmitter (Tx) side, a driver coil, five high-quality (Q) factor segmented resonators at different heights and orientations, and a closed-loop Tx power controller create a homogeneous electromagnetic (EM) field within the homecage 3-D space, and compensate for drops in power transfer efficiency (PTE) due to Rx misalignments. The headstage is equipped with four small slanted resonators, each covering a range of head orientations with respect to the Tx resonators, which direct the EM field toward the load coil at the bottom of the headstage. Moreover, data links based on Wi-Fi, UART, and Bluetooth low energy are utilized to enables remote communication and control of the Rx. The PTE varies within 23.6%–33.3% and 6.7%–10.1% at headstage heights of 8 and 20 cm, respectively, while continuously delivering >40 mW to the Rx electronics even at 90° rotation. As a proof of EnerCage-HC2 functionality in vivo, a previously documented on-demand electrical stimulation of the globus pallidus, eliciting consistent head rotation, is demonstrated in three freely behaving rats.

Towards a robust data link for intraoral tongue drive system using triple bands and adaptive matching

This paper presents the steps we have taken towards implementing a reliable and robust data link that is necessary for an intraoral Tongue Drive System (iTDS), which is a wireless and wearable assistive technology (AT). The iTDS detects the users intention from a set of user-defined commands that are defined based on tongue gestures to control wheelchair, phone, PC, etc. To deal with potential sources of RF interference, and add a certain level of redundancy, three operating bands, at 27 MHz, 433 MHz, and 915 MHz have been utilized and integrated in the compact circuit and system design. Additionally, to maintain high data link performance in the presence of tongue and jaw movements, which constantly change the loading on antennas, an adaptive matching network is incorporated in the transmitter (Tx) to deal with the dynamic oral environment for 433 MHz and 915 MHz bands, while sharing a dual-band antenna. An auto-tuning algorithm keeps the antenna matched, thanks to a feedback loop mechanism, which provides Voltage Standing Wave Ratio (VSWR) ≤ 2 match for the impedance with VSWR ≤ 4. The adaptive 3-band Tx chip is implemented in the TSMC035 standard CMOS process, and post-layout simulation results have been presented.

Towards a free-floating wireless implantable optogenetic stimulating system

This paper presents a wirelessly-powered and free-floating implantable optogenetic stimulating (FF-WIOS) implant with negligible footprint and high power transfer efficiency (PTE). FF-WIOS ASIC with embedded μLED and reflective lens is expected to stimulate the target cortical neuronal ensembles at high temporal and spatial resolution with minimal damage and no tethering effects. To improve the PTE, and stay below the SAR limit, a flexible planar transmitter (Tx) resonator, L2, will be implanted under the scalp, but over the skull. The Tx coil, L1, embedded in a headstage, L2 resonator, and a wire-bond receiver (Rx) coil, L3, wound around the FF-WIOS device, form a 3-coil inductive link operating at 135 MHz, which directly charges a surface-mount storage capacitor. At the onset of stimulation, the storage capacitor discharges into the μLED, while the stimulation parameters are sent to FF-WIOS by amplitude modulating of the power carrier. Post-layout simulation results show functionality of the storage capacitor charging, forward data transmission, and optogenetic stimulation with adjustable parameters.

Live demonstration: A smart homecage system with behavior analysis and closed-loop optogenetic stimulation capacibilities

In this live demonstration, we present a smart homecage system, called the Enercage-HC, with closed-loop wireless power transmission, wireless communication, and automated tracking and behavior recognition capabilities. Wireless power is delivered in near-field at 13.56 MHz in the FCC-approved ISM-band through an array of coils designed to provide the entire homecage with homogeneous magnetic field. Bidirectional data transmission is accomplished at 2.4 GHz via Bluetooth Low Energy (BLE) for communication with sensors and stimulators attached to or implanted in the animal body. A dual-mode 2D/3D imaging system based on Microsoft Kinect® is used for animal subject tracking and behavioral analysis.