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Bakhshaee Babaroud, N. (author), Rice, S.J. (author), Camarena, M. (author), Serdijn, W.A. (author), Vollebregt, S. (author), Giagka, Vasiliki (author)In this paper, we present the surface modification of multilayer graphene electrodes with platinum (Pt) nanoparticles (NPs) using spark ablation. This method yields an individually selective local printing of NPs on an electrode surface at room temperature in a dry process. NP printing is performed as a post-process step to enhance the...journal article 2024
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Rashidi, A. (author), Varkevisser, F. (author), Giagka, Vasiliki (author), Lopes Marta da Costa, T.M. (author), Serdijn, W.A. (author)Electrical stimulation is proven to be an effective way of neuromodulation in bioelectronic medicine (e.g. cochlear implants, deep brain stimulators, etc.), delivering localized treatment by the means of electrical pulses. To increase the stimulation efficiency and neural-type selectivity, there is an increasing interest to employ non...abstract 2023
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Savoia, Alessandro S. (author), Giustiniano, Domenico (author), Prelini, Carlo (author), Saccher, M. (author), Rashidi, A. (author), Leotti, Alberto (author), Giagka, Vasiliki (author), Ferrera, Marco (author)Micromachined Ultrasonic Transducers (MUTs) are being explored as power converters in wirelessly powered biomedical implants. This paper investigates the role of mechanical support properties in piezoelectric MUTs (PMUTs) on their power conversion efficiency. For this purpose, a finite element model (FEM) of a PMUT array was developed and...conference paper 2023
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Saccher, M. (author), Schaijk, Rob van (author), Kawasaki, Shinnosuke (author), Klootwijk, Johan H. (author), Rashidi, A. (author), Giagka, Vasiliki (author), Savoia, Alessandro Stuart (author), Dekker, R. (author)Capacitive Micromachined Ultrasound Transducers (CMUTs) have many advantages compared to other ultrasonic transducer technologies, especially for implantable devices. However, they require a high bias voltage for efficient operation. To eliminate the need for an external bias voltage, a charge storage layer can be embedded in the dielectric....conference paper 2023
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Saccher, M. (author), Rashidi, A. (author), Savoia, Alessandro Stuart (author), Giagka, Vasiliki (author), Dekker, R. (author)In the domain of ultrasonically powered biomedical implants, there is an increasing interest in cm-scale ultrasonic receivers (RX). However, when a single-element transducer is used as the RX transducer, an uneven phase distribution across the RX area can significantly reduce the harvestable power. In this paper, we investigate the impact of...conference paper 2023
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Rashidi, A. (author), Saccher, M. (author), Karuthedath, Cyril Baby (author), Sebastian, Abhilash Thanniyil (author), Savoia, Alessandro Stuart (author), Lavigne, Frederik (author), Stubbe, Frederic (author), Dekker, R. (author), Giagka, Vasiliki (author)Aluminum Nitride (AlN) Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are gaining interest for biomedical implant power due to biocompatibility and lowtemperature processing. However, due to the low piezoelectric coefficient of AlN PMUTs, storage capacitors are often used to accumulate ultrasonic power transferred over an extended...conference paper 2023
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Panskus, R. (author), Holzapfel, L.F.M. (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)Recording neuronal activity triggered by electrical impulses is a powerful tool in neuroscience research and neural engineering. It is often applied in acute electrophysiological experimental settings to record compound nerve action potentials. However, the elicited neural response is often distorted by electrical stimulus artifacts,...conference paper 2023
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Holzapfel, L.F.M. (author), Giagka, Vasiliki (author)Implantable devices need to communicate information to the outside world. For deep-seated miniaturized implants ultrasound communication can be favourable. However, implants need to operate during movement, and the selected communication scheme should be assessed accordingly. In this work, we implemented a simple protocol to transfer data...conference paper 2023
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Späth, Jana M. (author), Kolovou Kouri, K. (author), Holzapfel, L.F.M. (author), Thewes, Roland (author), Giagka, Vasiliki (author)Safety is a critical consideration when designing an electrical neural stimulator, given the direct contact with neural tissue. This paper presents the design of a charge balancing system suitable for frequencies up to the kilohertz domain, to be used as an add-on system for stimulators over a wide range of frequencies, also covering nerve...conference paper 2023
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Pola, M. (author), Giagka, Vasiliki (author), Serdijn, W.A. (author), Demarchi, Danilo (author), Rashidi, A. (author)This paper presents a new communication method between micro-scale freely floating brain implants based on galvanic coupling (GC), called "Brain-Coupled Communication" (BCC). Since the transmission efficiency based on GC is highly dependent on the system’s geometry and the electromagnetic properties of the tissue, finite element models in COMSOL...conference paper 2023
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Rashidi, A. (author), Rivandi, H. (author), Grubor, M. (author), Agostinho, Andre (author), Sadio, Valter (author), Santos, Marcelino (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)This paper presents a novel multi-channel stimulation backend with a multi-bit delta-sigma control loop, which enables precise adjustment of the stimulation current through modulation of the supply voltage. This minimizes the overhead voltage of series circuitry to the stimulation load and avoids the associated energy loss. Additionally, to...conference paper 2023
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Velea, A. (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)In an attempt to reduce the side effects caused by the chemically-based drugs used to treat neurological disorders, the field of bioelectronics has been focusing on the development of smart and reliable solutions that could, ideally, interact with the tissue at a resolution of individual cells.1 Conventionally, electrically-based systems have...abstract 2022
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Kolovou Kouri, K. (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)During the last few decades, electrical neural stimulators have successfully been employed as a means of treatment for a wide range of neurological disorders. By targeting the peripheral and central nervous systems, electrical neurostimulators activate/inhibit neural activity by manipulating the stimulus- induced electric field arising at the...abstract 2022
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Saccher, M. (author), Kawasaki, S. (author), Proietti Onori, Martina (author), van Woerden, Geeske M. (author), Giagka, Vasiliki (author), Dekker, R. (author)Background<br/>Microelectrode arrays (MEA) enable the measurement and stimulation of the electrical activity of cultured cells. The integration of other neuromodulation methods will significantly enhance the application range of MEAs to study their effects on neurons. A neuromodulation method that is recently gaining more attention is focused...journal article 2022
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Pak, A. (author), Nanbakhsh, K. (author), Hölck, Ole (author), Ritasalo, Riina (author), Sousa, Maria (author), Van Gompel, Matthias (author), Pahl, Barbara (author), Wilson, J.M. (author), Kallmayer, Christine (author), Giagka, Vasiliki (author)Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP...journal article 2022
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Panskus, R. (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)Over the past decades, neuromodulation has been proven to be an effective treatment for several neurological disorders. Moreover, it continues to be a rapidly evolving field with a wide-ranging potential for biomedical applications. However, efficient and patient-specific targeted neuromodulation remains one of the biggest challenges for...abstract 2022
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Bakhshaee Babaroud, N. (author), Palmar, M. (author), Velea, A. (author), Coletti, C. (author), Weingärtner, S.D. (author), Vos, F.M. (author), Serdijn, W.A. (author), Vollebregt, S. (author), Giagka, Vasiliki (author)Multimodal platforms combining electrical neural recording and stimulation, optogenetics, optical imaging, and magnetic resonance (MRI) imaging are emerging as a promising platform to enhance the depth of characterization in neuroscientific research. Electrically conductive, optically transparent, and MRI-compatible electrodes can optimally...journal article 2022
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Varkevisser, F. (author), Rashidi, A. (author), Lopes Marta da Costa, T.M. (author), Giagka, Vasiliki (author), Serdijn, W.A. (author)This work proposes a guideline for designing more energy-efficient electrical stimulators by analyzing the frequency spectrum of the stimuli. It is shown that the natural low-pass characteristic of the neuron’s membrane limits the energy transfer efficiency from the stimulator to the cell. Thus, to improve the transfer efficiency, it is proposed...conference paper 2022
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Kolovou Kouri, K. (author), Rashidi, A. (author), Varkevisser, F. (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)In neuromodulation applications, conventional current mode stimulation is often preferred over its voltage mode equivalent due to its good control of the injected charge. However, it comes at the cost of less energy-efficient output stages. To increase energy efficiency, recent studies have explored non-rectangular stimuli. The current work...conference paper 2022
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Kolovou Kouri, K. (author), Soloukey, Sadaf (author), Harhangi, Biswadjiet (author), Serdijn, W.A. (author), Giagka, Vasiliki (author)Spinal Cord Injury (SCI) is characterized by a disruption of the spinal pathways connecting the brain to the rest of the body. This can result in an impairment or complete loss of sensory and/or motor functions, depending on the level and severity of the injury. The most common approach of attempting motor recovery using neuromodulation has been...abstract 2021