@article{ahmmed_reynolds_bozkurt_2024, title={A Subcutaneously Injectable Implant for Multimodal Physiological Monitoring in Animals}, url={https://doi.org/10.1109/JSEN.2024.3366195}, DOI={10.1109/JSEN.2024.3366195}, abstractNote={Unobtrusive acquisition of physiological and behavioral data from freely moving animals is important to many applications including animal research, veterinary science, animal husbandry, and pet monitoring. This article reports a miniaturized, injectable, and multimodal implant for real-time measurements of heart rate (HR), breathing rate (BR), movement, and subcutaneous temperature with future extensions to blood pressure and oxygen saturation. To estimate these vital signs, the presented device incorporates sensors of various modalities: photoplethysmography, electrocardiography, accelerometry, magnetometry, and thermometry. A rechargeable battery drives the system containing a system-on-chip with Bluetooth low energy capability and multiple sensor front-end circuits. The implant electronics are isolated from the animal’s extracellular fluid by a dual-layer encapsulation of biomedical epoxy and poly(methyl methacrylate) that fits into a six-gauge surgical needle to allow for subcutaneous injection. Electrically conductive epoxy is used to create electrodes on the surface of the encapsulation for biopotential measurements. With a 3-m wireless range from a custom receiver, this implant can continuously transmit data from all the sensors for 20 h, which can support two–three months of duty-cycled and intermittent recording between battery recharges. The system was tested in vivo where the acquired HR and BR estimations showed an error of less than two beats per minute (BPM) compared to the gold standard. Longer-term evaluation of tissue reaction showed an acceptable level of immune responses with minimal effect on the sensing performance. This novel system has the potential to provide new insights with greater depth in veterinary research and practice, and animal welfare management.}, journal={IEEE Sensors Journal}, author={Ahmmed, Parvez and Reynolds, James and Bozkurt, Alper}, year={2024} }
 @article{zhao_stephany_han_ahmmed_bozkurt_jia_2023, title={A Wireless Multimodal Physiological Monitoring ASIC for Injectable Implants}, ISSN={["1930-8833"]}, DOI={10.1109/ESSCIRC59616.2023.10268719}, abstractNote={This paper presents a wireless multimodal physiological monitoring ASIC fabricated in a CMOS 180 nm process. The application-specific integrated circuit (ASIC) is sized to be within the form factor of an injectable microchip implant and can measure electrocardiography (ECG), photoplethysmography (PPG), and body temperature. The low-power circuit design enables the ASIC to wirelessly receive the required power, 155.3 μW on average, via an inductive link. The ECG analog frontend (AFE) has input-referred noise (IRN) of 3.1 μVrms within 0. 3-1kHz. To measure PPG, the LED driver employs a switched-capacitor-based architecture as an energy-efficient and safe method to deliver current pulses in milliampere order to an LED. An integrator-based AFE amplifies the photodetector (PD) current with 47 pArms IRN within 0.1-10 Hz. Recorded physiological signals are digitized by a 10-bit successive approximation register (SAR) analog-to-digital converter (ADC) with an 8.79-bit effective number of bits (ENOB), followed by a backscatter-based data telemetry, which transmits data via intermediate-frequency (IF)-assisted load shift keying (LSK) modulation. The overall ASIC performance has been evaluated in vivo on anesthetized rats.}, journal={IEEE 49TH EUROPEAN SOLID STATE CIRCUITS CONFERENCE, ESSCIRC 2023}, author={Zhao, Linran and Stephany, Raymond G. and Han, Yiming and Ahmmed, Parvez and Bozkurt, Alper and Jia, Yaoyao}, year={2023}, pages={305–308} }
 @article{queener_ahmmed_victorio_twiddy_dehn_brewer_lobaton_bozkurt_pozdin_daniele_2023, place={Vienna, Austria}, title={Conformal Micropatterned Organic-Metal Electrodes for Physiological Recording}, ISSN={["1930-0395"]}, url={http://dx.doi.org/10.1109/sensors56945.2023.10324963}, DOI={10.1109/SENSORS56945.2023.10324963}, abstractNote={Conformal electrodes provide a soft and conforming interface with the skin for reduced impedance, comfortable skin contact, and improved signal quality compared to commercial electrodes. In this paper, we present conformal micropatterned organic-metal (CMOM) electrodes and our investigation on the effect of perforation micropatterning and PEDOT:PSS coating. CMOM electrodes were characterized then evaluated in vivo against commercial-off-the-shelf electrodes. PEDOT:PSS was found to reduce the overall impedance in each electrode variant, resulting in a >97% decrease in impedance at low frequencies. The change in impedance at high frequencies was not significant for the control or $30\ \mu \mathrm{m}$ vias electrodes, but the impedance was significantly greater following EPD for $60\ \mu \mathrm{m}$ vias electrodes.}, journal={2023 IEEE SENSORS}, author={Queener, Kirstie M. and Ahmmed, Parvez and Victorio, Mauro and Twiddy, Jack and Dehn, Ashley and Brewer, Alec and Lobaton, Edgar and Bozkurt, Alper and Pozdin, Vladimir and Daniele, Michael}, year={2023} }
 @article{ahmmed_reynolds_bozkurt_regmi_2023, title={Continuous heart rate variability monitoring of freely moving chicken through a wearable electrocardiography recording system}, volume={102}, ISSN={["1525-3171"]}, url={https://doi.org/10.1016/j.psj.2022.102375}, DOI={10.1016/j.psj.2022.102375}, abstractNote={Identification and quantification of stress and stress inducing factors are important components of animal welfare assessment and essential parts of poultry management. Measurement of the autonomic nervous system's influence on cardiac function using heart rate and heart rate variability (HR/HRV) indices can provide a non-invasive assessment of the welfare status of an animal. This paper presents a preliminary study showing the feasibility of continuous long-term measurement of HR/HRV indices in freely moving chicken. We developed and evaluated an electrocardiography (ECG) based HR/HRV recording system that can be used as a poultry wearable backpack for research studies. The backpack system was first validated against a commercial ECG amplifier, and the corresponding estimations of HR values matched well with each other. Then, an in vivo proof-of-concept experiment was conducted on floor-reared chickens to collect ECG data for 2 weeks. The extracted HR/HRV values show strong alignment with circadian patterns and well-defined sleep cycles. Wearable devices, like the backpack ECG system used in this study, may be best suited for application in freely moving poultry to get an insight into circadian abnormalities and sleep quality for stress and welfare management.}, number={2}, journal={POULTRY SCIENCE}, author={Ahmmed, P. and Reynolds, J. and Bozkurt, A. and Regmi, P.}, year={2023}, month={Feb} }
 @article{reynolds_williams_martin_readling_ahmmed_huseth_bozkurt_2022, title={A Multimodal Sensing Platform for Interdisciplinary Research in Agrarian Environments}, volume={22}, ISSN={["1424-8220"]}, url={https://doi.org/10.3390/s22155582}, DOI={10.3390/s22155582}, abstractNote={Agricultural and environmental monitoring programs often require labor-intensive inputs and substantial costs to manually gather data from remote field locations. Recent advances in the Internet of Things enable the construction of wireless sensor systems to automate these remote monitoring efforts. This paper presents the design of a modular system to serve as a research platform for outdoor sensor development and deployment. The advantages of this system include low power consumption (enabling solar charging), the use of commercially available electronic parts for lower-cost and scaled up deployments, and the flexibility to include internal electronics and external sensors, allowing novel applications. In addition to tracking environmental parameters, the modularity of this system brings the capability to measure other non-traditional elements. This capability is demonstrated with two different agri- and aquacultural field applications: tracking moth phenology and monitoring bivalve gaping. Collection of these signals in conjunction with environmental parameters could provide a holistic and context-aware data analysis. Preliminary experiments generated promising results, demonstrating the reliability of the system. Idle power consumption of 27.2 mW and 16.6 mW for the moth- and bivalve-tracking systems, respectively, coupled with 2.5 W solar cells allows for indefinite deployment in remote locations.}, number={15}, journal={SENSORS}, author={Reynolds, James and Williams, Evan and Martin, Devon and Readling, Caleb and Ahmmed, Parvez and Huseth, Anders and Bozkurt, Alper}, year={2022}, month={Aug} }
 @article{ahmmed_reynolds_levine_bozkurt_2021, title={An Accelerometer-based Sensing System to Study the Valve-gaping Behavior of Bivalves}, ISSN={2475-1472}, url={http://dx.doi.org/10.1109/LSENS.2021.3067506}, DOI={10.1109/LSENS.2021.3067506}, abstractNote={Bivalves are extremely sensitive to environmental conditions. The movement of their shells and the gap in-between the valves can serve as indicators of water pollutants entering surface water bodies. This letter proposes a novel sensing system to accurately calculate the valve-gaping angle in bivalves. The sensor unit is comprised of two inertial measurement units for each bivalve to estimate the angle between the two valves. Monitoring of multiple bivalves is possible with several water-insulated sensor units tethered with flexible cables to a central base station housing the processing unit. Miniaturization of the sensor packaging and flexibility of the wires ensured minimum hindrance to the animals’ natural behavior. The precision and accuracy of the angle measurement were tested with a benchtop servo motor setup simulating the gaping behavior. The standard deviation of measurements at a steady state was 0.78<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula>, and the average change in measurement during a 10<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> step was 9.98<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula>. Over 250 h of <italic>in vivo</italic> validation experiments demonstrated the consistency of the angle measurements using the presented method alongside a magnetic alternative, which had an average correlation coefficient of <inline-formula><tex-math notation="LaTeX">$-$</tex-math></inline-formula>0.89. The sensor system provides an accurate study of bivalve gaping behavior and facilitates the potential use of bivalves as environmental sentinels due to their valve-gaping being a biomarker for monitoring water pollution.}, journal={IEEE Sensors Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Ahmmed, Parvez and Reynolds, James and Levine, Jay F and Bozkurt, Alper}, year={2021}, pages={1–1} }
 @article{ahmmed_holder_foster_castro_patel_torfs_bozkurt_2021, title={Noncontact Electrophysiology Monitoring Systems for Assessment of Canine-Human Interactions}, ISSN={["1930-0395"]}, url={http://dx.doi.org/10.1109/sensors47087.2021.9639748}, DOI={10.1109/sensors47087.2021.9639748}, abstractNote={Canine-assisted interactions have enormous potential in coping with psychological disorders and stress. It has been actively used for improving the mood of hospitalized patients, especially those suffering from chronic diseases like cancer. However, little progress has been made to enable the assessment of these interactions between the patient and the animal in a quantitative and undisruptive way. In this paper, we present a capacitively coupled biopotential recording system custom-designed for animal-human dyads. This system uses noncontact electrodes to monitor the heart rate and its variability to evaluate the physiological basis of the animal-assisted therapies. Preliminary in vivo evaluation of the system in humans and canines demonstrates promising measurement accuracy. The mean absolute error of the estimated heart rate was less than 0.25 BPM in reference to a commercial electrocardiography device. The future integration of this system into ergonomic form factors could enable a better understanding of animal-human interactions during canine-assisted therapy sessions by realizing an unobtrusive and continuous monitoring platform.}, journal={2021 IEEE SENSORS}, publisher={IEEE}, author={Ahmmed, Parvez and Holder, Timothy and Foster, Marc and Castro, Ivan D. and Patel, Aakash and Torfs, Tom and Bozkurt, Alper}, year={2021} }
 @article{ahmmed_reynolds_hamada_regmi_bozkurt_2021, title={Novel 3D-printed Electrodes for Implantable Biopotential Monitoring}, ISSN={["1558-4615"]}, url={http://dx.doi.org/10.1109/embc46164.2021.9630055}, DOI={10.1109/embc46164.2021.9630055}, abstractNote={A major bottleneck in the manufacturing process of a medical implant capable of biopotential measurements is the design and assembly of a conductive electrode interface. This paper presents the use of a novel 3D-printing process to integrate conductive metal surfaces on a low-temperature co-fired ceramic base to be deployed as electrodes for electrocardiography (ECG) implants for small animals. In order to fit the ECG sensing system within the size of an injectable microchip implant, the electronics along with a pin-type lithium-ion battery are inserted into a cylindrical glass tube with both ends sealed by these 3D printed composite electrode discs using biomedical epoxy. In the scope of this paper, we present a proof-of-concept in vivo experiment for recording ECG from an avian animal model under local anesthesia to verify the electrode performance. Simultaneous recording with a commercial device validated the measurements, demonstrating promising accuracy in heart rate and breathing rate monitoring. This novel technology could open avenues for the mass manufacturing of miniaturized ECG implants.Clinical relevance— A novel manufacturing process and an implantable system are presented for continuous physiological monitoring of animals to be used by veterinarians, animal scientists, and biomedical researchers with potential future applications in human health monitoring.}, journal={2021 43RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY (EMBC)}, publisher={IEEE}, author={Ahmmed, Parvez and Reynolds, James and Hamada, Shu and Regmi, Prafulla and Bozkurt, Alper}, year={2021}, pages={7120–7123} }
 @article{songkakul_wu_ahmmed_reynolds_zhu_bozkurt_2021, title={Wearable Bioimpedance Hydration Monitoring System using Conformable AgNW Electrodes}, ISSN={["1930-0395"]}, url={http://dx.doi.org/10.1109/sensors47087.2021.9639469}, DOI={10.1109/sensors47087.2021.9639469}, abstractNote={Monitoring hydration level could be vital for maintaining physiological and cognitive performance during physical exertion and thermal stress. We present a custom miniaturized wearable bioimpedance spectroscopy (BIS) system consisting of a Bluetooth-enabled system-on-a-chip and an analog front-end circuit integrated with conformable, flexible, and stretchable silver-nanowire electrodes. This system is capable of performing four-electrode BIS at a range of frequencies between 5 kHz and 195 kHz, transmitting the data wirelessly to a data aggregator, and configuring the front-end circuit parameters over-the-air when needed. A 150 mAh lithium polymer battery can power the system for 18 hours. In this study, proof-of-concept in-vitro validation of the system generated promising results.}, journal={2021 IEEE SENSORS}, publisher={IEEE}, author={Songkakul, Tanner and Wu, Shuang and Ahmmed, Parvez and Reynolds, William D., Jr. and Zhu, Yong and Bozkurt, Alper}, year={2021} }
 @article{valero-sarmiento_ahmmed_bozkurt_2020, title={In Vivo Evaluation of a Subcutaneously Injectable Implant with a Low-Power Photoplethysmography ASIC for Animal Monitoring}, volume={20}, ISSN={["1424-8220"]}, url={https://doi.org/10.3390/s20247335}, DOI={10.3390/s20247335}, abstractNote={Photoplethysmography is an extensively-used, portable, and noninvasive technique for measuring vital parameters such as heart rate, respiration rate, and blood pressure. The deployment of this technology in veterinary medicine has been hindered by the challenges in effective transmission of light presented by the thick layer of skin and fur of the animal. We propose an injectable capsule system to circumvent these limitations by accessing the subcutaneous tissue to enable reliable signal acquisition even with lower light brightness. In addition to the reduction of power usage, the injection of the capsule offers a less invasive alternative to surgical implantation. Our current prototype combines two application-specific integrated circuits (ASICs) with a microcontroller and interfaces with a commercial light emitting diode (LED) and photodetector pair. These ASICs implement a signal-conditioning analog front end circuit and a frequency-shift keying (FSK) transmitter respectively. The small footprint of the ASICs is the key in the integration of the complete system inside a 40-mm long glass tube with an inner diameter of 4 mm, which enables its injection using a custom syringe similar to the ones used with microchip implants for animal identification. The recorded data is transferred wirelessly to a computer for post-processing by means of the integrated FSK transmitter and a software-defined radio. Our optimized LED duty cycle of 0.4% at a sampling rate of 200 Hz minimizes the contribution of the LED driver (only 0.8 mW including the front-end circuitry) to the total power consumption of the system. This will allow longer recording periods between the charging cycles of the batteries, which is critical given the very limited space inside the capsule. In this work, we demonstrate the wireless operation of the injectable system with a human subject holding the sensor between the fingers and the in vivo functionality of the subcutaneous sensing on a pilot study performed on anesthetized rat subjects.}, number={24}, journal={SENSORS}, author={Valero-Sarmiento, Jose Manuel F. and Ahmmed, Parvez and Bozkurt, Alper}, year={2020}, month={Dec} }
 @inproceedings{a wearable wrist-band with compressive sensing based ultra-low power photoplethysmography readout circuit_2019, url={https://ieeexplore.ieee.org/document/8771074}, DOI={10.1109/bsn.2019.8771074}, abstractNote={In this paper, we present our efforts towards packaging of a novel compressive sampling (CS) based ultra-low power photoplethysmography (PPG) application-specific integrated circuit (ASIC) into a wearable form factor. The system comprises of a custom PPG analog front-end circuit, integrated with a digital back-end to enable CS, and a commercial off-the-shelf (COTS) system-on-chip (SoC) for Bluetooth Low Energy (BLE) based wireless data transfer. The ASIC consumes $172 [\pmb \mu \mathrm{W}$ power to extract heart rate from the sparse PPG signal where the whole system consumes 1.66 mW power for continuous streaming of heart rate data over the COTS BLE radio. This work presents the first ever demonstration of a CS based PPG ASIC in wrist-band form factors and paves our way towards deploying and evaluating this custom PPG ASIC in future clinical studies. The modular architecture of the wristband platform allows for incorporation of other sensors for future correlated sensing studies between health and environment.}, booktitle={2019 IEEE 16th International Conference on Wearable and Implantable Body Sensor Networks (BSN)}, year={2019}, month={May} }
 @article{reynolds_ahmmed_bozkurt_2019, title={An Injectable System for Subcutaneous Photoplethysmography, Accelerometry, and Thermometry in Animals}, volume={13}, ISSN={["1940-9990"]}, url={https://doi.org/10.1109/TBCAS.2019.2923153}, DOI={10.1109/TBCAS.2019.2923153}, abstractNote={Obtaining physiological data from animals in a non-obtrusive and continuous manner is important to veterinary science. This paper demonstrates the design and deployment of a miniaturized capsule-based system for subdermal injection to provide real-time and continuous heart-rate, movement, and core-body-temperature measurements. The presented device incorporates sensors for photoplethysmography, motion detection, and temperature measurements. A bluetooth-low-energy enabled microcontroller configures the sensors, digitizes the sensor information, and wirelessly connects with external devices. The device is powered by a CR425 battery for this paper, and various other battery solutions are available based upon the use case. The design uses only commercially available integrated circuits in order to reduce the development cost and be modular. The encapsulation is a combination of medical epoxy and poly(methyl methacrylate) that fits within a 6-gauge hypodermic needle. The preliminary evaluation of the device included an in vitro assessment of its thermal response and measurement accuracy, the impact of one-month implantation on surrounding tissue, the power consumption with duty cycling of various sensors, and a measurement of physiological signals in a rat and a chicken. Having a form factor and implantation method similar to existing devices for animals, this novel system is a useful platform for both scientists and veterinarians to better study a diverse range of animals.}, number={5}, journal={IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Reynolds, James and Ahmmed, Parvez and Bozkurt, Alper}, year={2019}, month={Oct}, pages={825–834} }
 @inproceedings{reynolds_ahmmed_bozkurt_2018, title={Preliminary Evaluation of an Injectable Sensor for Subcutaneous Photoplethysmography in Animals}, url={https://ieeexplore.ieee.org/document/8584775}, DOI={10.1109/biocas.2018.8584775}, abstractNote={This paper demonstrates the construction and preliminary evaluation of a capsule system that can be easily injected under the skin of animals for real-time photoplethysmography. The presented device incorporates three light-emitting diodes, a photodiode, a microprocessor, and a Bluetooth Low Energy transceiver into a miniaturized package made of poly(methyl methacrylate). In order to provide a low-cost solution, this generation of the device is constructed with only commercial off-the-shelf electronic components. A low-power electronic design addresses concerns about the thermal effects on the surrounding tissue. The heart rate monitoring accuracy is comparable to that of traditional electrocardiography measured with subdermal needle electrodes on rat models. We expect this work to lay the foundation for a novel tool to provide biomedical researchers and veterinarians with a continuous and real-time measurement of heart rate through subcutaneous wireless photoplethysmography.}, booktitle={2018 IEEE Biomedical Circuits and Systems Conference (BioCAS)}, publisher={IEEE}, author={Reynolds, James and Ahmmed, Parvez and Bozkurt, Alper}, year={2018}, month={Oct} }
 @inproceedings{roy_ahmmed_rahman_ash-saki_harun-ur-rashid_2014, title={A novel adaptive volterra filter to compensate for speaker non-linearity}, DOI={10.1109/ICECE.2014.7026856}, abstractNote={The implementation of an adaptive Volterra filter to compensate for speaker non-linearity using a pipelined recurrent neural network based architecture is demonstrated. The proposed architecture consists of two stages: nonlinear stage performing a nonlinear second order Volterra (SOV) mapping from the input space to an intermediate space and a linear combiner performing a linear mapping from the intermediate space to the output space. The filter design is tested by implementing it on a dataplane processing unit configured for audio processing. The implemented algorithm is adjusted for Xtensa Processor and uses HiFi-2 DSP standard. The collected data confirms smaller error of the output with the speaker and also a very low settling time.}, booktitle={8th International Conference on Electrical and Computer Engineering}, author={Roy, T. and Ahmmed, P. and Rahman, M. S. and Ash-Saki, A. and Harun-Ur-Rashid, A. B. M.}, year={2014}, pages={258–261} }
 @inproceedings{ahmmed_ahmed_rafee_awal_choudhury_2014, title={Self-localization of a mobile robot using monocular vision of a chessboard pattern}, DOI={10.1109/ICECE.2014.7026828}, abstractNote={A computationally fast visual approach of autonomous robot localization with high degree of accuracy is demonstrated. Relative position and orientation of an autonomous robot with respect to a fixed reference point is determined by minimal processing of a monocular image employing projective geometry resulting in very low computational requirements. A three-layered sequential algorithm i.e. Detection-Pixel Level Analysis-Sub Pixel Accuracy, is used to speed up the process and to reduce computational bulk. The position coordinate of a point in a plane is obtained by analyzing the perspective projection of a reference structure on a monocular image perceived by a camera placed at that point. A chessboard pattern is suitably chosen as the reference structure which is placed at the origin of the plane.}, booktitle={8th International Conference on Electrical and Computer Engineering}, author={Ahmmed, P. and Ahmed, Z. and Rafee, M. I. J. and Awal, M. A. and Choudhury, S. M.}, year={2014}, pages={753–756} }
 @inproceedings{ahmmed_saha_sunny_hossain_rafee_2013, title={Modeling and simulation of a Microcontroller based power factor correction converter}, DOI={10.1109/ICIEV.2013.6572713}, abstractNote={A Microcontroller based power factor correction (PFC) converter is proposed, which is not affected by harmonic distortion in current and voltage wave shapes. This paper describes the design and simulation of a single-phase PFC converter using Atmel's AVR Microcontroller. It involves sensing and measuring the power factor from the load using ADC; implementing faster algorithm to process the data using discrete time filter which requires least amount of memory; and triggering appropriate capacitors in order to compensate the excessive reactive components. A power factor near to unity is thus achieved, which results higher efficiency and low-THD AC output. A provision for measuring the power is also discussed.}, booktitle={2013 International Conference on Informatics, Electronics and Vision (ICIEV)}, author={Ahmmed, P. and Saha, S. S. and Sunny, S. M. N. A. and Hossain, M. I. and Rafee, M. I. J.}, year={2013}, pages={1–4} }