Publications by authors named "Edwin Kan"

14 Publications

  • Page 1 of 1

Furniture-Integrated Respiration Sensors by Notched Transmission Lines.

IEEE Sens J 2021 Feb 6;21(4):5303-5311. Epub 2020 Oct 6.

School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.

Non-invasive respiration sensors integrated into furniture can be invisible to the user and greatly enhance comfort and convenience to facilitate many applications. Current sensors often require user cooperation or fitting, which discourages frequent usage. We present a new respiration sensor integrated into a bed or a chair by modifying a radio-frequency (RF) coaxial cable structure with a designed notch. The lung motion is coupled to the electromagnetic leakage at the notch through near-field coherent sensing (NCS). The sensors, covered with fabrics and positioned under the abdomen and thorax, can capture the respiratory waveforms and derive the breath rate. The heart rate can also be evaluated in the same setup with proper filtering. The sensor design can tolerate large position variation to accommodate user uncertainties. Various voluntary exercises of normal, deep, fast, held and blocked breathing were measured under different postures of supine, recumbent and sitting by the carrier frequency range between 900MHz and 2.4GHz. The breath rate from 10 participants compare well with the synchronous commercial chest-belt sensors in all breathing routines.
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http://dx.doi.org/10.1109/jsen.2020.3028970DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7978236PMC
February 2021

Wearable radio-frequency sensing of respiratory rate, respiratory volume, and heart rate.

NPJ Digit Med 2020 28;3:98. Epub 2020 Jul 28.

School of Electrical and Computer Engineering, Cornell University, Ithaca, NY USA.

Many health diagnostic systems demand noninvasive sensing of respiratory rate, respiratory volume, and heart rate with high user comfort. Previous methods often require multiple sensors, including skin-touch electrodes, tension belts, or nearby off-the-body readers, and hence are uncomfortable or inconvenient. This paper presents an over-clothing wearable radio-frequency sensor study, conducted on 20 healthy participants (14 females) performing voluntary breathing exercises in various postures. Two prototype sensors were placed on the participants, one close to the heart and the other below the xiphoid process to couple to the motion from heart, lungs and diaphragm, by the near-field coherent sensing principle. We can achieve a satisfactory correlation of our sensor with the reference devices for the three vital signs: heart rate ( = 0.95), respiratory rate ( = 0.93) and respiratory volume ( = 0.84). We also detected voluntary breath-hold periods with an accuracy of 96%. Further, the participants performed a breathing exercise by contracting abdomen inwards while holding breath, leading to paradoxical outward thorax motion under the isovolumetric condition, which was detected with an accuracy of 83%.
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http://dx.doi.org/10.1038/s41746-020-0307-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7387475PMC
July 2020

A Wearable RF Sensor for Monitoring Respiratory Patterns

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:1217-1223

We present a non-invasive approach for continuous monitoring of respiration dynamics using a wearable radio-frequency (RF) sensor based on near-field coherent sensing. A continuous-wave RF signal at 1.8 GHz is generated by a software-defined radio, with both transmitter (Tx) and receiver (Rx) antennas placed close to the xiphoid process. The experimental prototype of the mobile sensor can modulate the internal organ motion in the near-field region of the Tx antenna and is then received by the nearby Rx antenna to be demodulated and sampled. Through peak detection, we have identified inhalation and exhalation peaks of each breath cycle to estimate the breath rate and the lung volume. The extracted respiratory parameters are compared with the conventional chest belts data for various simulated respiratory conditions including voluntary deep, fast-shallow and slow-shallow breathing. We also characterized simulated central sleep apneas, Cheyne-Stokes, Biot's, ataxic and coughing conditions. To accurately identify obstructive apnea, we presented a two-sensor approach that can capture paradoxical movement of thorax and abdomen. The on-line recognition of these respiratory patterns can be employed not only to continuously monitor patients with chronic respiratory disorders but also to provide real-time feedback for future therapeutic purposes.
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http://dx.doi.org/10.1109/EMBC.2019.8857870DOI Listing
July 2019

Breathable and Flexible Piezoelectric [email protected] Fibrous Nanogenerator for Wearable Applications.

Polymers (Basel) 2018 Jul 5;10(7). Epub 2018 Jul 5.

Department of Fiber Science and Apparel Design, Cornell University, Ithaca, NY 14853, USA.

A novel breathable piezoelectric membrane has been developed by growing zinc oxide (ZnO) nanorods on the surface of electrospun poly(vinylidene fluoride) (PVDF) nanofibers using a low-temperature hydrothermal method. Significant improvement in the piezoelectric response of the PVDF membrane was achieved without compromising breathability and flexibility. PVDF is one of the most frequently used piezoelectric polymers due to its high durability and reasonable piezoelectric coefficient values. However, further enhancement of its piezoelectric response is highly desirable for sensor and energy-harvester applications. Previous studies have demonstrated that piezoelectric ceramic and polymer composites can have remarkable piezoelectric properties and flexibility. However, devices made of such composites lack breathability and some present health risks in wearable applications for containing heavy metals. Unlike other piezoelectric ceramics, ZnO is non-toxic material and has been widely used in many applications including cosmetics. The fabrication of [email protected] porous electrospun membrane involves a simple low-temperature ZnO growth in aqueous solution, which does not weaken the polarization of PVDF created during electrospinning in the high electric field.
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http://dx.doi.org/10.3390/polym10070745DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403693PMC
July 2018

No-touch measurements of vital signs in small conscious animals.

Sci Adv 2019 02 13;5(2):eaau0169. Epub 2019 Feb 13.

School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.

Measuring the heartbeat and respiration of small conscious animals is important for assessing their health and behavior, but present techniques such as electrocardiogram (ECG), ultrasound, and auscultation rely on close skin contact with the animal. These methods can also require surface preparation, cause discomfort or stress to animals, and even require anesthetic administration, especially for birds, reptiles, and fish. Here, we show that radio frequency near-field coherent sensing (NCS) can provide a new solution to animal vital sign monitoring while ensuring minimal pain and distress. We first benchmarked NCS with synchronous ECG on an anesthetized rat. NCS was then applied to monitor a conscious hamster from outside its cage, and was further extended to a parakeet, Russian tortoise, and betta fish in a noninvasive manner. Our system can revolutionize vital sign monitoring of small conscious animals in their laboratory living quarters or natural habitats.
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http://dx.doi.org/10.1126/sciadv.aau0169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374106PMC
February 2019

Simultaneous optical and electrical in vivo analysis of the enteric nervous system.

Nat Commun 2016 06 7;7:11800. Epub 2016 Jun 7.

School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.

The enteric nervous system (ENS) is a major division of the nervous system and vital to the gastrointestinal (GI) tract and its communication with the rest of the body. Unlike the brain and spinal cord, relatively little is known about the ENS in part because of the inability to directly monitor its activity in live animals. Here, we integrate a transparent graphene sensor with a customized abdominal window for simultaneous optical and electrical recording of the ENS in vivo. The implanted device captures ENS responses to neurotransmitters, drugs and optogenetic manipulation in real time.
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http://dx.doi.org/10.1038/ncomms11800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899629PMC
June 2016

A real-time spike classification method based on dynamic time warping for extracellular enteric neural recording with large waveform variability.

J Neurosci Methods 2016 Mar 21;261:97-109. Epub 2015 Dec 21.

School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.

Background: Computationally efficient spike recognition methods are required for real-time analysis of extracellular neural recordings. The enteric nervous system (ENS) is important to human health but less well-understood with few appropriate spike recognition algorithms due to large waveform variability.

New Method: Here we present a method based on dynamic time warping (DTW) with high tolerance to variability in time and magnitude. Adaptive temporal gridding for "fastDTW" in similarity calculation significantly reduces the computational cost. The automated threshold selection allows for real-time classification for extracellular recordings.

Results: Our method is first evaluated on synthesized data at different noise levels, improving both classification accuracy and computational complexity over the conventional cross-correlation based template-matching method (CCTM) and PCA+k-means clustering without time warping. Our method is then applied to analyze the mouse enteric neural recording with mechanical and chemical stimuli. Successful classification of biphasic and monophasic spikes is achieved even when the spike variability is larger than millisecond in width and millivolt in magnitude.

Comparison With Existing Method(s): In comparison with conventional template matching and clustering methods, the fastDTW method is computationally efficient with high tolerance to waveform variability.

Conclusions: We have developed an adaptive fastDTW algorithm for real-time spike classification of ENS recording with large waveform variability against colony motility, ambient changes and cellular heterogeneity.
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http://dx.doi.org/10.1016/j.jneumeth.2015.12.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4749467PMC
March 2016

Non-Faradaic Electrochemical Detection of Exocytosis from Mast and Chromaffin Cells Using Floating-Gate MOS Transistors.

Sci Rep 2015 Dec 21;5:18477. Epub 2015 Dec 21.

Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.

We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry.
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http://dx.doi.org/10.1038/srep18477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4685269PMC
December 2015

Programmable ion-sensitive transistor interfaces. III. Design considerations, signal generation, and sensitivity enhancement.

Phys Rev E Stat Nonlin Soft Matter Phys 2014 May 30;89(5):052817. Epub 2014 May 30.

Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.

We report on factors that affect DNA hybridization detection using ion-sensitive field-effect transistors (ISFETs). Signal generation at the interface between the transistor and immobilized biomolecules is widely ascribed to unscreened molecular charges causing a shift in surface potential and hence the transistor output current. Traditionally, the interaction between DNA and the dielectric or metal sensing interface is modeled by treating the molecular layer as a sheet charge and the ionic profile with a Poisson-Boltzmann distribution. The surface potential under this scenario is described by the Graham equation. This approximation, however, often fails to explain large hybridization signals on the order of tens of mV. More realistic descriptions of the DNA-transistor interface which include factors such as ion permeation, exclusion, and packing constraints have been proposed with little or no corroboration against experimental findings. In this study, we examine such physical models by their assumptions, range of validity, and limitations. We compare simulations against experiments performed on electrolyte-oxide-semiconductor capacitors and foundry-ready floating-gate ISFETs. We find that with weakly charged interfaces (i.e., low intrinsic interface charge), pertinent to the surfaces used in this study, the best agreement between theory and experiment exists when ions are completely excluded from the DNA layer. The influence of various factors such as bulk pH, background salinity, chemical reactivity of surface groups, target molecule concentration, and surface coatings on signal generation is studied. Furthermore, in order to overcome Debye screening limited detection, we suggest two signal enhancement strategies. We first describe frequency domain biosensing, highlighting the ability to sort short DNA strands based on molecular length, and then describe DNA biosensing in multielectrolytes comprising trace amounts of higher-valency salt in a background of monovalent saline. Our study provides guidelines for optimized interface design, signal enhancement, and the interpretation of FET-based biosensor signals.
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http://dx.doi.org/10.1103/PhysRevE.89.052817DOI Listing
May 2014

Programmable ion-sensitive transistor interfaces. II. Biomolecular sensing and manipulation.

Phys Rev E Stat Nonlin Soft Matter Phys 2013 Jul 1;88(1):012802. Epub 2013 Jul 1.

School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.

The chemoreceptive neuron metal-oxide-semiconductor transistor described in the preceding paper is further used to monitor the adsorption and interaction of DNA molecules and subsequently manipulate the adsorbed biomolecules with injected static charge. Adsorption of DNA molecules onto poly-L-lysine-coated sensing gates (SGs) modulates the floating gate (FG) potential ψ(O), which is reflected as a threshold voltage shift measured from the control gate (CG) V(th_CG). The asymmetric capacitive coupling between the CG and SG to the FG results in V(th_CG) amplification. The electric field in the SG oxide E(SG_ox) is fundamentally different when we drive the current readout with V(CG) and V(ref) (i.e., the potential applied to the CG and reference electrode, respectively). The V(CG)-driven readout induces a larger E(SG_ox), leading to a larger V(th_CG) shift when DNA is present. Simulation studies indicate that the counterion screening within the DNA membrane is responsible for this effect. The DNA manipulation mechanism is enabled by tunneling electrons (program) or holes (erase) onto FGs to produce repulsive or attractive forces. Programming leads to repulsion and eventual desorption of DNA, while erasing reestablishes adsorption. We further show that injected holes or electrons prior to DNA addition either aids or disrupts the immobilization process, which can be used for addressable sensor interfaces. To further substantiate DNA manipulation, we used impedance spectroscopy with a split ac-dc technique to reveal the net interface impedance before and after charge injection.
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http://dx.doi.org/10.1103/PhysRevE.88.012802DOI Listing
July 2013

Programmable ion-sensitive transistor interfaces. I. Electrochemical gating.

Phys Rev E Stat Nonlin Soft Matter Phys 2013 Jul 1;88(1):012801. Epub 2013 Jul 1.

School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.

Electrochemical gating is the process by which an electric field normal to the insulator electrolyte interface shifts the surface chemical equilibrium and further affects the charge in solution [Jiang and Stein, Langmuir 26, 8161 (2010)]. The surface chemical reactivity and double-layer charging at the interface of electrolyte-oxide-semiconductor (EOS) capacitors is investigated. We find a strong pH-dependent hysteresis upon dc potential cycling. Varying salinity at a constant pH does not change the hysteretic window, implying that field-induced surface pH regulation is the dominant cause of hysteresis. We propose and investigate this mechanism in foundry-made floating-gate ion-sensitive field-effect transistors, which can serve as both an ionic sensor and an actuator. Termed the chemoreceptive neuron metal-oxide-semiconductor (CνMOS) transistor, it features independently driven control gates (CGs) and sensing gates (SGs) that are capacitively coupled to an extended floating gate (FG). The SG is exposed to fluid, the CG is independently driven, and the FG is capable of storing charge Q(FG) of either polarity. Asymmetric capacitive coupling between the CG and SG to FG results in intrinsic amplification of the measured surface potential shifts and influences the FG charge injection mechanism. This modified SG surface condition was monitored through transient recordings of the output current, performed under alternate positive and negative CG pulses. Transient recordings revealed a hysteresis where the current was enhanced under negative pulsing and reduced after positive pulsing. This hysteresis effect is similar to that observed with EOS capacitors, suggesting a field-dependent surface charge regulation mechanism at play. At high CG biases, nonvolatile charge Q(FG) tunneling into the FG occurs, which creates a larger field and tunes the pH response and the point of zero charge. This mechanism gives rise to surface programmability. In this paper we describe the operational principles, tunneling mechanism, and role of electrolyte composition under field modulation. The experimental findings are then modeled by a Poisson-Boltzmann formulation with surface pH regulation. We find that surface ionization constants play a dominant role in determining the pH tuning effect. In the following paper [K. Jayant et al., Phys. Rev. E 88, 012802 (2013)] we extend the dual-gate operation to molecular sensing and demonstrate the use of Q(FG) to achieve manipulation of surface-adsorbed DNA.
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http://dx.doi.org/10.1103/PhysRevE.88.012801DOI Listing
July 2013

Field modulation in bilayer graphene band structure.

J Phys Condens Matter 2009 Mar 30;21(10):102202. Epub 2009 Jan 30.

School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.

Using an external electric field, one can modulate the band gap of Bernal stacked bilayer graphene by breaking the A-[Formula: see text] symmetry. We analyze strain effects on the bilayer graphene using the extended Hückel theory and find that reduced interlayer distance results in higher band gap modulation, as expected. Furthermore, above about 2.5 Å interlayer distance, the band gap is direct, follows a convex relation with the electric field and saturates to a value determined by the interlayer distance. However, below about 2.5 Å, the band gap is indirect, the trend becomes concave and a threshold electric field is observed, which also depends on the stacking distance.
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http://dx.doi.org/10.1088/0953-8984/21/10/102202DOI Listing
March 2009

Non-Faradaic electrochemical detection of protein interactions by integrated neuromorphic CMOS sensors.

Biosens Bioelectron 2008 May 16;23(10):1503-11. Epub 2008 Jan 16.

School of Electrical and Computer Engineering, Cornell University Ithaca, 323 Phillips Hall, Ithaca, NY 14853 USA.

Electronic detection of the binding event between biotinylated bovine serum albumen (BSA) and streptavidin is demonstrated with the chemoreceptive neuron MOS (CnuMOS) device. Differing from the ion-sensitive field-effect transistors (ISFET), CnuMOS, with the potential of the extended floating gate determined by both the sensing and control gates in a neuromorphic style, can provide protein detection without requiring analyte reference electrodes. In comparison with the microelectrode arrays, measurements are gathered through purely capacitive, non-Faradaic interactions across insulating interfaces. By using a (3-glycidoxypropyl)trimethoxysilane (3-GPS) self-assembled monolayer (SAM) as a simple covalent link for attaching proteins to a silicon dioxide sensing surface, a fully integrated, electrochemical detection platform is realized for protein interactions through monotone large-signal measurements or small-signal impedance spectroscopy. Calibration curves were created to coordinate the sensor response with ellipsometric measurements taken on witness samples. By monitoring the film thickness of streptavidin capture, a sensitivity of 25ng/cm2 or 2A of film thickness was demonstrated. With an improved noise floor the sensor can detect down to 2ng/(cm2mV) based on the calibration curve. AC measurements are shown to significantly reduce long-term sensor drift. Finally, a noise analysis of electrochemical data indicates 1/f(alpha) behavior with a noise floor beginning at approximately 1Hz.
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http://dx.doi.org/10.1016/j.bios.2008.01.006DOI Listing
May 2008

Electrolyte pulse current measurements by CvMOS with microsecond and thermal voltage resolution.

Conf Proc IEEE Eng Med Biol Soc 2006;2006:1846-9

Sch. of Electr. & Comput. Eng., Cornell Univ., Ithaca, NY 14853, USA.

Non-invasive, charge-based sensing in chemoreceptive neuron MOS (CvMOS) transistors with extended floating-gate structure has brought forth features that are beneficial to the system integration of biological sensing. This paper presents the results of fast electrolytic signal detection on silicon dioxide, which advances possible technologies for rapid DNA discrimination or external monitoring of cell action potentials.
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http://dx.doi.org/10.1109/IEMBS.2006.260209DOI Listing
March 2008