Research

Diagnostic & Therapeutic Systems:

1. An Ultrasonically Powered Implantable Micro Electrolytic Ablation for Tumor Necrosis

Electrolytic ablation is a technique that can remove non- resectable tumors from internal organs (such as liver, kidney, pancreas, etc.) with highly localized control to minimize harm to adjoining healthy tissue. Here, we aim to utilize the principle of electrolytic ablation in an implantable platform and power it by an external ultrasonic wave. The implantable micro electrolytic ablation (IMEA) will address challenges of the current existing tethered method such as constraints in electrode size, multiple targets and repeated treatments in case of cancer recurrence. We characterized the prototype of IMEA in an agarose gel containing phenolphthalein to simulate internal body tissue. Color change in phenolphthalein shows that the device responds to external ultrasonic stimulation and shows electrolytic behavior in an area around the electrodes that spreads outward with time. Overall, the IMEA could achieve 0.614±0.01 cm2 in ablation area (cathode) when ~190 mW/cm2 ultrasonic intensity was applied for 60min.

2. An Ultrasonically Powered Implantable Micro-Light Source for Localized Photodynamic Therapy

In this work, we introduce an ultrasonically powered light source which can provide in-situ localized light for Photodynamic Therapy. The implants are 2×2×2mm3 and 2×4×2mm3 in dimensions and consist of two red LEDs mounted on a piezoelectric energy source. Such device is small enough to be easily implanted inside solid tumors using a biopsy needle. In-vitro light intensity measurements show an output power density of 48 μW/cm2 from the 2×2×2mm3 and 1.1 mW/cm2 from the 2×4×2mm3 light source. The results indicate that implanting multiple sources and powering them for 1 hour can provide optimal energy for localized Photodynamic Therapy.

3. A Wireless Intracranial Brain Deformation Sensing System for Blast-Induced Traumatic Brain Injury

Blast-induced traumatic brain injury (bTBI) has been linked to a multitude of delayed-onset neurodegenerative and neuropsychiatric disorders, but the complete understanding of their pathogenesis remains elusive. To develop mechanistic relationships between bTBI and post-blast neurological sequelae, it is imperative to characterize the initiating traumatic mechanical events leading to eventual alterations of cell, tissue, and organ structure and function. This paper presents a wireless sensing system capable of monitoring the intracranial brain deformation in real-time during the event of a bTBI. The system consists of an implantable soft magnet and an external head-mounted magnetic sensor that is able to measure the field in three dimensions. The change in the relative position of the soft magnet respect to the external sensor as the result of the blast wave induces changes in the magnetic field. The magnetic field data, in turn, is used to extract the temporal and spatial motion of the brain under the blast wave in real-time. The system has temporal and spatial resolutions of 5 ms and 10 mm. Following the characterization and validation of the sensor system, we measured brain deformations in a live rodent during a bTBI.


Telemedicine: 

1. An Implantable Pressure Sensing System With Electromechanical Interrogation Scheme

We report on an implantable pressure sensing system that is powered by mechanical vibrations in the music’s frequency range. This technique significantly enhances interrogation range, alleviates the misalignment issues commonly encountered with inductive powering, and simplifies the external receiver circuitry. The interrogation scheme consists of two phases: a mechanical vibration phase and an electrical radiation phase. During the first phase, a piezoelectric cantilever acts as an acoustic receiver and charges a capacitor by converting sound vibration harmonics occurring at its resonant frequency into electrical power. In the subsequent electrical phase, when the cantilever is not vibrating, the stored electric charge is discharged across an LC tank whose inductor is pressure sensitive; hence, when the LC tank oscillates at its natural resonant frequency, it radiates a high-frequency signal that is detectable using an external receiver and its frequency corresponds to the measured pressure. The pressure sensitive inductor consists of a planar coil (single loop of wire) with a ferrite core whose distance to the coil varies with applied pressure. A prototype of the implantable pressure sensor is fabricated and tested, both in vitro and in vivo (swine bladder).


Biosensors: 

1. An Implantable Wireless Interstitial Pressure Sensor With Integrated Guyton Chamber: in vivo Study in Solid Tumors

A wireless implantable interstitial fluid pressure (IFP) sensor with an integrated Guyton chamber is presented. This implantable device enables noninvasive and continuous measurements of IFP. The Guyton chamber allows for an accurate measurement of interstitial fluid pressure without the interference from various cellular/tissue components. The sensor consists of a coil, an air chamber, a silicone membrane embedded with a nickel plate, and a Guyton chamber. The fabricated device is 3 mm in diameter and 1 mm in thickness. The sensor shows a linear response to the pressure with a sensitivity of 60 kHz/mmHg and a resolution of 1 mmHg. Experiments in human prostate cancer tumors grown in mice confirm the sensor’s capability to operate in vivo and provide a continuous wireless measurement of IFP, a surrogate parameter indicating the “window of opportunity” for delivering chemo- and radiotherapeutic agents.


Wearable Health Systems: 

1. A Wearable Smartphone-Enabled Camera- Based System for Gait Assessment

Quantitative assessment of gait parameters provides valuable diagnostic and prognostic information. However, most gait analysis systems are bulky, expensive, and designed to be used indoors or in laboratory settings. Recently, wearable systems have attracted considerable attention due to their lower cost and portability. In this paper, we present a simple wearable smartphone-enabled camera-based system (SmartGait) for measurement of spatiotemporal gait parameters. We assess the concurrent validity of SmartGait as compared to a commercially available pressure-sensing walkway (GaitRite®). Fifteen healthy young adults (25.8 ±. 2.6 years) were instructed to walk at slow, preferred, and fast speed. The measures of step length (SL), step width (SW), step time (ST), gait speed, double support time (DS) and their variability were assessed for agreement between the two systems; absolute error and intra-class correlation coefficients (ICC) were determined. Measured gait parameters had modest to excellent agreements (ICCs between 0.731 and 0.982). Overall, SmartGait provides many advantages and is a strong alternative wearable system for laboratory and community-based gait assessment.