@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} }
 @article{pamula_valero-sarmiento_yan_bozkurt_van hoof_van helleputte_yazicioglu_verhelst_2017, title={A 172 mu W Compressively Sampled Photoplethysmographic (PPG) Readout ASIC With Heart Rate Estimation Directly From Compressively Sampled Data}, volume={11}, ISSN={["1940-9990"]}, DOI={10.1109/tbcas.2017.2661701}, abstractNote={A compressive sampling (CS) photoplethysmographic (PPG) readout with embedded feature extraction to estimate heart rate (HR) directly from compressively sampled data is presented. It integrates a low-power analog front end together with a digital back end to perform feature extraction to estimate the average HR over a 4 s interval directly from compressively sampled PPG data. The application-specified integrated circuit (ASIC) supports uniform sampling mode (1x compression) as well as CS modes with compression ratios of 8x, 10x, and 30x. CS is performed through nonuniformly subsampling the PPG signal, while feature extraction is performed using least square spectral fitting through Lomb–Scargle periodogram. The ASIC consumes 172 $\mu$ W of power from a 1.2 V supply while reducing the relative LED driver power consumption by up to 30 times without significant loss of relevant information for accurate HR estimation.}, number={3}, journal={IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS}, author={Pamula, Venkata Rajesh and Valero-Sarmiento, Jose Manuel and Yan, Long and Bozkurt, Alper and Van Hoof, Chris and Van Helleputte, Nick and Yazicioglu, Refet Firat and Verhelst, Marian}, year={2017}, month={Jun}, pages={487–496} }
 @inproceedings{rajesh_valero-sarmiento_yan_bozkurt_van hoof_van helleputte_yazicioglu_verhelst_2016, title={A 172 mu W compressive sampling photoplethysmographic readout with embedded direct heart-rate and variability extraction from compressively sampled data}, volume={59}, booktitle={2016 ieee international solid-state circuits conference (isscc)}, author={Rajesh, P. V. and Valero-Sarmiento, J. M. and Yan, L. and Bozkurt, A. and Van Hoof, C. and Van Helleputte, N. and Yazicioglu, R. F. and Verhelst, M.}, year={2016}, pages={386–541} }
 @inproceedings{brugarolas_valero-sarmiento_bozkurt_essick_2016, title={Auto-adjusting mandibular repositioning device for in-home use}, DOI={10.1109/embc.2016.7591677}, abstractNote={Obstructive Sleep Apnea (OSA) is a form of respiratory dysfunction that affects 20% of adults in the world. Among the first-line treatments that are used to mitigate the effects of OSA are continuous positive airway pressure (CPAP) and mandibular repositioning devices (MRD). Although CPAP provides a more efficacious therapy than MRDs, recent studies suggest that both are comparable in overall effectiveness due to greater patient preference and adherence to MRD therapy. In this paper, we present the Auto-Positioner, a novel add-on for MRDs that adjusts the extent to which the mandible (lower jaw) is advanced in response to respiratory signals indicating labored breathing during sleep, and to changes in sleeping position known to affect individual patient's airway patency.}, booktitle={2016 38th annual international conference of the ieee engineering in medicine and biology society (embc)}, author={Brugarolas, R. and Valero-Sarmiento, J. M. and Bozkurt, A. and Essick, G. K.}, year={2016}, pages={4296–4299} }
 @inproceedings{brugarolas_valero-sarmiento_brna_2015, title={Wearable SpO(2) and sleep posture monitoring system for obstructive sleep apnea patients}, booktitle={2015 Virtual Conference on Application of Commercial Sensors}, author={Brugarolas, R. and Valero-Sarmiento, J. M. and Brna, A.}, year={2015} }