With a growing interest in real-time control of prostheses and wearable rehabilitation devices to treat motor dysfunction, there is a need to classify normal and abnormal body movement using kinematic and electrophysiological data. This paper presents a novel linear algorithm that can classify 10 distinct neck movements based on signals of only four surface electromyography (sEMG) electrodes. We here report on data of 5 healthy adults performing the 10 different neck movements: flexion/extension, right/left lateral flexion, right/left rotation, and four multiplanar directions. Surface EMG electrodes were attached to five locations: 1) left and right sternocleidomastoid, 2) left and right trapezius, and 3) the C7 spinal segment as reference. The algorithm yielded an accuracy of 92.5% in classifying six single-planar neck movement directions and an average accuracy of 81.2% in classifying all ten directions. The algorithm's performance was validated by comparing its accuracy with two conventional classification methods: Linear Discriminant Analysis (LDA) and Artificial Neural Network (ANN). The algorithm has 40% higher accuracy compared to LDA and the comparable accuracy of a three-layer ANN. The linearity and simplicity of the our algorithm enables its deployment on low-cost processors and systems. Future research will be focused on the classification of more complex neck movements and applications in neuromodulation devices.

A Calibration is one of the key processes to design and implement of Bioelectrical Impedance Spectroscopy. Through the simulation, the specification of hardware can be determined and examined in the ideal condition. After the implementation of the device, the theoretical and measured values are different due to the uncertainties and noises from the environment. In this paper, the calibration procedure will be introduced and discussed for the different sets of electrodes. By adjusting the different values of the active electrodes and applying for the active shields, the measured value will be compared and discussed. Active electrodes and active shields will be a very effective way to isolate and minimize the noises and avoid unwanted stray capacitance values. Further investigations need to be followed to ensure the proposed way to reduce the noises and stray capacitances.

Cell transfection by electroporation is a biological assay that has been utilized to inject exogenous molecules (e.g.: RNA, DNA and protein) into live cells. Recently, electroporation has been utilized in developing cell therapy for cancer (e.g., CAR T-cell). One of the major drawbacks in current electroporation methods is the cell death during the process. These dead cells can be detrimental, if injected back to the patients. Current cell filtering methods are unable purify T-cells following electroporation, this is due to the lack of unique biomarkers that target the apoptosis and necrosis of T-cells. To address this issue, we have developed a method using dielectrophoresis and microfluidics, where no prior labeling is needed to isolate dead cells from live cells. Upon electroporation, the cell sample has to be flowed through the microfluidic chip where a selective electric field is applied through specially designed electrodes so that the dead cells are trapped on the electrodes, and the live cells are able to flow through and are collected at the end. Results after purification of the cells using our method reveal that it is possible to achieve ∼100% of purity in filtering of the live cells. This method presents a viable solution to a critical concern regarding CAR T-cell manufacturing. This paper presents an extended study of the variation of efficacy in the design with the time from the electroporation.

Approximately 500,000 dialysis patients in America are at a high risk of hyperkalemia, a condition where blood potassium becomes elevated above normal levels. Hyperkalemia is extremely dangerous, as it can result in severe cardiac complications if untreated. Hyperkalemia may be silent or present vague symptoms until those complications develop, at which point patients require emergency medical care. However, if patients have the ability to measure their potassium levels at home, they could detect hyperkalemia before it reaches a dangerous stage, and seek preventative medical care to avoid severe complications. Therefore, we have designed a novel device allowing patients to measure their blood potassium levels at home. The workflow of our solution is as follows: (1) patients obtain a blood sample from a finger prick, (2) potassium concentration is measured with an ion specific electrode (ISE), and (3) the device displays their potassium levels and a recommended course of action based on their hyperkalemic risk. We validate our solution with three major tests. First, our portable ISE technology must accurately measure potassium concentration in blood samples. Second, appropriate lancet parameters (gauge and depth) to minimize hemolysis in capillary blood samples must be found to minimize falsely elevated readings. Third, device portability and ease of use must be evaluated using patient input, as these factors will affect patient compliance. We have validated the use of portable ISE technology to feasibly measure potassium, and we continue to collect data for our second and third tests.

Electroanatomical mapping systems are being utilized clinically for locating arrhythmias within a given patient’s heart. Today, employed endocardial mapping systems are invasive and require extensive set-up time. Epicardial mapping systems, like CardioInsight™ from Medtronic, are non-invasive but require co-registration of electrodes to the heart, e.g. via a required Computed Tomography (CT) scan. This system has been used both clinically and in several laboratories in situ. The difficulties with in vitro uses are that the ex vivo perfused hearts lack an associated thoracic cavity, resulting in the possibility of inconsistent placement of electrodes, and poor conduction of epicardial signals. We are developing in our laboratory means to use the CardioInsight™ system on reanimated large mammalian hearts. Preliminary studies were conducted on swine hearts, but this system could be also be utilized with reanimated human hearts, making this research even more translatable. The use of this epicardial mapping system will allow for critical observations during pacing or ablation experiments and for collecting critical data for computational modeling.

Drowsiness, a transitional psychological state between alertness and sleepiness, is one of the leading reasons for the increased risk of accidents, particularly in commercial aviation. Though electroencephalography (EEG) is widely used for drowsiness assessment, it is impractical for unobtrusive airborne monitoring due to discomfort induced by the number of electrodes touching the scalp. In this work, we investigated the potential of pulse arrival time (PAT), and photoplethysmogram (PPG) features as indicators of drowsiness. Simultaneous vertical electrooculogram (EOG), ear PPG, and electrocardiogram (ECG) were recorded from 18 commercially-rated pilots from 02:00 AM to 04:30 AM. ECG R-peaks and PPG peaks were detected and used for calculation of PAT and heart rate to observe their changes during drowsiness. During the drowsy periods, the PAT and RR intervals increased (i.e., decrease in heart rate) significantly (p < 0.05) compared to baseline. Features based on only PPG also showed a significant increase during drowsiness. However, decrease in PAT/RR during drowsiness for most of the subjects indicates that increase in PAT is not linearly correlated to RR interval and might be reflecting changes in arterial stiffness. Hence, PAT and derived PPG based features with continuous heart rate monitoring can serve as useful indicators of early drowsiness detection.

Endoscopic radiofrequency ablation has gained interest for treating abdominal tumors. The radiofrequency ablation electrode geometry largely determines the size and shape of the ablation zone. Mismatch between the ablation zone and tumor shapes leads to reoccurrence of the cancer. Recently, work has been published regarding a novel deployable multi-tine electrode for endoscopic radiofrequency ablation. The prior work developed a thermal ablation model to predict the ablation zone surrounding an electrode and a systematic optimization of the electrode shape to treat a specific tumor shape. The purpose of this work is to validate the thermal ablation model through experiments in a tissue phantom that changes color at ablation temperatures. The experiments highlight the importance of thermal tissue damage in finite element modeling. Thermal induced changes in tissue properties, if not accounted for in finite element modeling, can lead to significant overprediction of the expected ablation zone surrounding an electrode.

The purpose of this examination was to determine a) how bioimpedance scanning generates data about the human body and b) compare the Bodystat Multiscan 5000 and the Skulpt Chisel. The Bodystat Multiscan 5000 is bioelectrical impedance spectroscopy (BIS) device that performs a scan of 50 measurements, from 5 kHz to 1000 kHz. This scan generates a 2d Cole analysis plot that compares the resistance and reactance of the scanned muscle group. Higher frequencies measure the amount of intracellular fluid (ICF), and lower frequencies measure the amount of extracellular fluid (ECF). Lower values for the resistance and reactance relate to a greater level of fitness for the scanned area. The Skulpt Chisel is an electrical impedance myography (EIM) that performs a single 50 kHz measurement. This scan determines the muscle quality and percent body fat of the scanned muscle group. The test subject was scanned with each device. Each plane was scanned three times with the Bodystat Multiscan 5000, and scanned five times with the Skulpt Chisel. The data was recorded to Excel and analyzed using MATLAB. The Bodystat Multiscan measurements for the surfaces were examined at a frequency of 50 kHz to be comparable to the Skulpt Chisel data. The surfaces are recorded in descending order of magnitude for resistance: medial, 22.14 Ω; anterior, 20.31 Ω; posterior, 17.89 Ω; lateral, 12.6 Ω. The Cole Analysis for the right thigh at 45-degree intervals are recorded in descending order of magnitude for resistance: medial/posterior, 23.89 Ω; posterior/lateral, 23.06 Ω; anterior/medial, 21.09 Ω; lateral/anterior, 16.13 Ω. The Skulpt Chisel surfaces are recorded in an increasing order of magnitude, the first value being muscle quality and the second value being percent body fat: lateral, 81.12, 13.1%; posterior, 62.22, 16.46%; anterior, 50.88, 19.24%; medial, 42.16, 23.16%. The data display an inverse relationship between resistance/reactance and muscle quality, and a direct relationship between resistance/reactance and percent body fat. The larger the magnitude of the resistance/reactance recorded for a muscle group, the lower the level of muscle quality will be. This leads to a larger percent body fat value.

The degree to which deep brain stimulation (DBS) therapy can effectively treat various brain disorders depends on how well one can selectively stimulate one or more axonal pathways within the brain. There is rapidly growing clinical interest in DBS lead implant designs with electrode arrangements that can better target axonal pathways of interest, especially in cases where the optimal target is immediately adjacent to a pathway that when stimulated will elicit adverse side effects. Numerical modeling has demonstrated that DBS leads with four radially segmented electrodes provide the best balance of directional targeting capability while minimizing the overall number of electrode contacts [1]. Here, we present a novel 4×4 DBS lead (16-channel electrode array) with the same form factor and materials as current 4 or 8-channel FDA-approved DBS leads. Electrode impedance spectroscopy was performed for three of these 4×4 DBS leads showing reliable electrode impedances before and after implantation within the brain.

Image-guided, minimally-invasive cochlear implant surgery is a novel “keyhole” surgical approach for placing a cochlear implant electrode array eliminating the need for a wide-field mastoidectomy approach. Image guidance is used for path planning which is followed by the construction of a customized micro-stereotactic frame to drill a narrow channel from the skull surface to the cochlea. Herein, we present an insertion tool that uses roller wheels to advance the electrode array through the narrow tunnel and into the cochlea. Testing in a phantom revealed that when compared to insertions with surgical forceps, the new insertion tool was on average 26s faster, produced complete insertions more often (i.e. in 6/6 trials, vs. 1/6), and reduced array buckling (0/6 trials vs. 5/6). The tool provides a viable solution to complete the last step of this novel, minimally-invasive procedure. It also provides the advantage over previously developed manual insertion tools of enabling the surgeon to blindly actuate the roller wheel tool to advance the electrode into the tunnel. This allows the surgeon to visualize and guide insertion into the cochlea from a more advantageous visual perspective.

Two different methods of attaching the current leads for segmental bioelectrical impedance analysis measurements were compared. The first method was leaving the current electrodes in place at the hand and foot for all measurements, while the second method involved moving the current electrodes to be adjacent to the voltage electrodes when measuring each segment. Each method was compared to a whole-body measurement performed at the same occasion as the segmental measurements. Slight deviation from the whole-body measurement was expected, as the electrode placements resulted in small gaps that were not measured between each of the arm, trunk, and leg segments. The second method, moving the current electrodes for each segment, was found to be the closer of the two methods for whole body measurements, with errors of 2% and 5.8% at R 0 and R ∞ , respectively, while the first method had errors of 4.2% and 6% respectively.

In high-frequency (“HF”) monopolar electrosurgery (or radio-frequency ablation), high current density causes heating of tissue adjacent to a surgical instrument. HF current passes through tissue at a frequency sufficiently high to avoid stimulation of muscle, but intentionally causes I 2 R heating of tissue for the purposes of ablation, dissection, and coagulation. In addition to the surgical tool, a Neutral Electrode (“NE”, often called a “ground pad”, “return electrode”, or simply “pad”) contacts the patient to complete the electrical circuit, as shown in Fig. 1.

Thermal ablation is rapidly becoming a standard of care for the treatment of atrial fibrillation (AF), a cardiac disorder characterized by irregular heart rhythm and estimated to impact more than 33 million people worldwide [1]. AtriCure is a company that specializes in epicardial ablation for AF and here we describe the development of a numerical model to study the performance of the Isolator ® Synergy™ Clamp bipolar radiofrequency (RF) device. The clamp device features two jaws with embedded electrode pairs, which are used to secure the tissue by clamping across the left atrium (as shown in Figure 1). Energy is applied between the bipolar electrodes at approximately 460 kHz through an impedance-based control algorithm and is additionally duty-cycled between the pairs to further distribute the heating. Patient anatomies vary greatly and measured impedance will depend on atrial wall thickness, epicardial fat, electrode-tissue engagement, and structural variations. Further, tissue conductivity (inversely related to impedance) increases as the tissue is heated, leading to a complicated process, where the heat generation depends on the impedance, which in turn is a strong function of temperature. Energy delivery continues until a phase change in the tissue’s water content occurs, producing a sharp increase in impedance and termination of the ablation. Therefore, since tissue impedance and heating drive the device’s performance, a majority of the effort described here focuses on the validation work done to ensure the model is based on an accurate description of the tissue properties and response. While previous modeling of RF ablation often does include temperature-dependence of tissue properties, the referenced values vary notably and rarely include direct validation of modeling results to benchtop data. Variations in anatomy and fat content can dramatically impact the energy delivery and patient-to-patient treatment efficacy, so an accurate description of the tissue response is critical to understanding the limitations of current energy delivery algorithms and provides an invaluable tool in designing more efficacious ablation devices and algorithms.

Maintaining upright stance is a complex process, it requires appropriate functioning of a postural control system which consists of inputs from somatosensory, vestibular, musculoskeletal, and proprioceptive systems as well as from several brain regions [1–4]. A concussion is defined as a brain injury caused due to unexpected acceleration/deceleration of the head causing temporary alteration of brain function and it is a prevalent source of injury to football athletes [1]. With the altered function of the brain, the ability to maintain postural equilibrium becomes challenging due to the inability of individuals to respond promptly to stressors, thus, making maintenance of postural equilibrium rather difficult for individuals with a concussion. Effects of concussion on postural ability are shown to last up to three days post injury [5]. Postural stability test, therefore, can be performed to make a valid return to play (RTP) decision, pre-mature RTP is shown to have been catastrophic due to its potential to permanently impair previously affected region/functioning [1,5]. Postural sway data (center of pressure, COP) is traditionally analyzed to study the postural control. Therefore, COP can provide critical information regarding individual’s ability to maintain upright stance post injury. A more sensitive concussion assessment tool based on electroencephalogram (EEG) is used to accurately track effects of concussion [6]. However, sophisticated electrode placement requirement inhibits its immediate applicability. In current preliminary research, we attempt to differentiate athletes with a history of concussion (experimental) from healthy (control) using postural data. In order to do so, a concept of empirical mode decomposition (EMD) was adopted. EMD has shown evidence in the literature to infer vital information pertaining to the complex underlying physiological phenomenon [4, 7–8]. In the current research, the resultant COP (COPr) was decomposed into its finite set of band-limited signals termed as intrinsic mode functions (IMFs) [8], a set of linear and nonlinear features were extracted from COPr and its IMfs. Lastly, a test of significance was conducted to infer the potential of postural data for differentiating concussed from healthy athletes.

Hepatocellular carcinoma (HCC), commonly known as the liver cancer, is a severe health concern worldwide. For patients with liver tumors that are difficult to remove through traditional treatments such as radiation, chemotherapy and partial hepatectomy, there is the option of radiofrequency ablation (RFA) treatment. RFA is a minimally invasive procedure that is currently treating liver tumors that are relatively small in size. Radiofrequency ablation uses currents to heat up the tissue of the tumor. Once the temperature of the tissue reaches approximately 60° C tissue necrosis begins to occur [1]. With current RFA probes, ablation lesions are typically 3–5.5 cm in diameter [2]. It is important that all of the tumor tissue is ablated, so it is necessary to also kill a small amount of the surrounding healthy tissue. At least 1 cm of healthy tissue should be ablated to ensure the tumor will not recur [2]. Hence, many studies [3, 4] have attempted to increase the RFA ablation zone through various methods including adding saline to the tissue, predicting the optimal power level, etc. To focus on safely increasing the size of the ablation zone and to improve upon the spherical geometry of the tumors, the “Christmas tree” and “umbrella” style probes [5], which utilize multi-pronged electrodes (tines), are currently available in the market. The electrodes, or wires of the probe, are responsible for producing heat and making contact with the liver tissue at all time in order to execute the tissue ablation. For the umbrella and Christmas tree style probes, the drawbacks include: 1. the gauge of the tines limit the ablation scope of the probes; 2. their ability to achieve higher volumes of cell death are limited due to their static geometry, which has fixed diameters; 3. towards the outer edge of the tumor, due to their static geometry and the loss of contact with live tissues, the rate of killing cancerous cells decreases drastically due to the decrease in heat transfer rate, which is a result of the lack of heat sink from perfusion in the live tissues [6]. It was noticed that an improvement could be made to the efficiency of these multi-pronged electrodes if they were free to expand as the area of tissue was ablated. Therefore, a novel dynamic RFA probe was proposed by Lau and Han and numerical simulations using COMSOL Multiphysics Joule heating module have concluded that this dynamic RFA probe can achieve a higher ablation volume with a shorter procedure time [7]. The main goal of this study is to realize the design of this dynamic RFA probe with expandable electrodes to create the largest and most replicable ablation zone. In this study, the deployment mechanism and the proposed design of the dynamic probe are discussed and the analytical solutions of the electrode expansion profiles are presented. The ablation zones are estimated analytically based on the dynamic expansion of the electrodes.

Deep Brain Stimulation (DBS) has demonstrated outstanding results for the treatment of medically intractable Parkinson’s disease (PD), essential tremor and other neurological and psychiatric disorders, such as Obsessive Compulsive Disorder (OCD) and major depression [1,2]. Despite widespread proliferation, efficacy of DBS treatment is limited primarily because of two key limitations as shown in Fig. 1: (a) non-specific activation of regions implicated in DBS side effects, and (b) inefficient neurostimulation due to complex anatomical structure and axonal orientations of target regions. Thus, there is a need to develop approaches to DBS that achieve more precise target selection and efficient activation of axonal pathways within the brain. Recent efforts in target selection has focused on shaping the stimulation field by using multichannel electrodes for current steering [3]. These multichannel electrodes are limited to cylindrical lead configuration and can only correct for small spatial localization errors, and they do not utilize the direction of the electrical field’s gradients to stimulate neurons depending on their orientation (mainly orientation of axons). Thus, there is a critical need for new electrode architectures that enable both spatial steering and stimulation field orientation tuning capabilities. Here we present the Flex-DBS, a novel DBS electrode lead architecture that harnesses recent advances in flexible probe fabrication and precision guidance strategy to mechanically reconfigure electrodes in three dimensional orientations within anatomically complex brain tissue. Further, it incorporates dense arrays of electrodes with each lead that allow stimulation field orientation tuning.

Electrotherapeutic devices require an electrode for coupling with the body. The most common electrodes are made of conducting corrosion resistance materials (e.g., TiN, Ir-IrO 2 , Pt) plus a coupling layer (e.g., electrolyte). The electrode is the location where redox reaction take place between the device and the tissue. As such, it must conduct both electrons and ions. The reactions can be capacitive, involving the charging and discharging of the electrode-electrolyte double layer, or faradaic. Capacitive charge-injection is more desirable than faradic charge-injection because no chemical species are created or consumed during a stimulation pulse. Most noble metal based electrodes are faradic or pseudo-capacitive, which can lead to performance changes over time. In addition, under the high rate of charge injection and high current density conditions of a neuromuscular stimulation pulse, access to all the accessible charges is limited by the interfacial resistance and low surface area at the electrode [1]. A particularly critical point is the passage of current between the surface of the skin and the electrical contact connected by wire to the device, which requires a low stable resistance that does not vary with time, humidity [2]. We have developed new hybrid mixed-ionic-electronic conductors (MIECs) that have the potential to overcome these deficiencies. The MIECs are an interconnected network of electrical and ionic conductors in an elastomeric matrix that provide: (1) high surface area for efficient capacitive charge-discharge; (2) high ionic conductivity for low interfacial resistance; (3) low ohmic resistance; and (4) excellent flexibility and toughness. Carbon nanotubes (CNTs) are the electrical conductors in the MIEC and hyaluronic acid (HA), along with moisture and ions, is the ionic conductor. Unlike the current state-of-the-art, conducting noble metals, this system exhibits good mechanical properties, high conductivity (up to 3000 mS/cm), high moisture retention (up to 100wt%) and high ion mobility, leading to facile electrode kinetics. This simple yet efficient system is promising for the fabrication of a variety of high performance flexible electrodes.

Recently, high intensity focused ultrasound (HIFU) has been used for non-invasive surgery of prostate, uterus, and brain. However, a HIFU therapy is suffered from relatively long surgical time mainly due to small focal area per each sonication. In order to solve this problem, a HIFU therapy using multi-frequency was suggested by several researchers, and they demonstrated that this technique can increase the area of the coagulated lesion due to enhanced cavitation effect compared to single-frequency HIFU [1–3]. To generate multi-frequency especially dual-frequency, dual-element and dual-layer HIFU transducers have been developed and provided an expanded lesion size [1–3]. In this study, we present an alternative technique of making dual-frequency HIFU transducer using inversion layer technique. Generally, a single layer piezoelectric element can excite the strong fundamental resonance (f 0 ) and the weak odd-order harmonic resonance (3f 0 ) [4]. In the inversion layer technique, on the other hand, a piezoelectric component consisting of two piezo-ceramic plates bonded together with opposite poling directions and different thicknesses can produce the relatively strong even-order harmonic (2f 0 ) in addition to the fundamental resonance [5]. Additionally, only a pair of electrode at the outside of the each piezo-ceramic plate is required to stimulate dual-frequency ultrasound while two pairs of electrodes are typically required for conventional dual-element and dual-layer transducers [2,3]. A specially designed prototype HIFU transducer was built, and we verified that the dual-frequency ultrasound was successfully generated through electrical impedance and pulse-echo response measurements.

A brain-computer interface (BCI) is a device that uses brain signals to provide a non-muscular communication channel [1], particularly for individuals with severe neuromuscular disabilities. One of the most promising signals for controlling a BCI are event-related potentials (ERPs) such as the P300. The P300 event related potential is an evoked response to an external stimulus that has been traditionally observed in scalp-recorded electroencephalography (EEG). The scalp-recorded P300 response has proven to be a reliable signal for controlling a BCI using the P300 Speller paradigm [2]. Recent studies have demonstrated that the P300 Speller has the potential to serve as an effective communication device for persons who have lost or are losing the ability to write and speak.

We report on the development of a polymeric layer consisting of an embedded channel network. The channels are filled with a thermally responsive polymer. The embedded thermally responsive polymer is in solid phase in room ambient, but changes to liquid at physiological body temperature (∼37 °C). This phase change results in the polymer structure changing to a more flexible state. An important application of this polymer layer is its use as a thermally regulated support structure for a gastric pacing electrode, to give some rigidity to the electrode body preferable during implantation surgery, while changing to a more flexible state inside the body as the embedded polymer subsequently melts at physiological temperature. The latter is expected to reduce complications caused by a rigid device.