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Item type:Publication, Access status: without files , Electronic measurement systems for osteosynthesis implants and external fixatorsPublicationtype: Doctoral Thesis65 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , 3.35V High Voltage Electroforming System in 28nm with 5.3mV ripple and 46 % efficiency for HfO2-based Memristors(Elsevier, 2025-10-01); ; ; ; This work demonstrates an on-chip high voltage (HV) generation, which is a critical requirement for memristor electroforming (EF) but is typically absent in smaller technology nodes. Key achievements of this study includes: (1) the development of a three-stage charge pump (CP) with an efficiency of 46.5%, delivering an EF voltage VEF of 3.35V with a compliance current Icc of 184.9μA from a 1.8V supply voltage Vdd, without the need for HV-transistors in 28nm CMOS process, and is based on preliminary work presented at the 20th International Conference on Synthesis, Modeling, Analysis and Simulation Methods and Applications to Circuit Design (SMACD) in Volos, Greece (Shamookh et al., 2024); (2) the electrostatic discharge (ESD) protection, meeting the requirements of Class C3 CDM (±300V) and Class 1C HBM (±1.5kV) as per JEDEC standards (Semenov et al., 2008), employing three ESD diodes to handle positive (>3.3V) triggering ESD events and a single ESD diode for negative triggering ESD events above −1.87V; and (3) the on-chip EF architecture for a 64 × 64 memristor crossbar array, as an active matrix (AM), through source and gate control of the compliance transistor. A ripple detection stage monitors voltage ripple at the three-stage CP bit-line (BL), halting gate pulses to the active compliance transistor and triggering EF for the next memristor in the left-to-right sequence. The proposed design is scalable to any m×n array and adaptable to various memristor applications, paving the way for fully integrated EF solutions in advanced technology nodes.Publicationtype: Journal Article18 18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Spatially Localized Visual Perception Estimation by Means of Prosthetic Vision Simulation(Multidisciplinary Digital Publishing Institute (MDPI), 2024-11-18); Retinal prosthetic devices aim to repair some vision in visually impaired patients by electrically stimulating neural cells in the visual system. Although there have been several notable advancements in the creation of electrically stimulated small dot-like perceptions, a deeper comprehension of the physical properties of phosphenes is still necessary. This study analyzes the influence of two independent electrode array topologies to achieve single-localized stimulation while the retina is electrically stimulated: a two-dimensional (2D) hexagon-shaped array reported in clinical studies and a patented three-dimensional (3D) linear electrode carrier. For both, cell stimulation is verified in COMSOL Multiphysics by developing a lifelike 3D computational model that includes the relevant retinal interface elements and dynamics of the voltage-gated ionic channels. The evoked percepts previously described in clinical studies using the 2D array are strongly associated with our simulation-based findings, allowing for the development of analytical models of the evoked percepts. Moreover, our findings identify differences between visual sensations induced by the arrays. The 2D array showed drawbacks during stimulation; similarly, the state-of-the-art 2D visual prostheses provide only dot-like visual sensations in close proximity to the electrode. The 3D design could offer a technique for improving cell selectivity because it requires low-intensity threshold activation which results in volumes of stimulation similar to the volume surrounded by a solitary RGC. Our research establishes a proof-of-concept technique for determining the utility of the 3D electrode array for selectively activating individual RGCs at the highest density via small-sized electrodes while maintaining electrochemical safety.Publicationtype: Journal Article12 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Design optimization of high voltage generation for memristor electroforming in 28nm CMOS(IEEE, 2024-11); ; ; ; The process of electroforming (EF) a memristor involves setting the channel resistance via current compliance Icc. This EF phase varies in duration based on the EF voltage VEF, requiring high voltage (HV) as a trade-off with EF time. To achieve CMOS-memristor scalable co-integration, on-chip HV-generation is essential. This study presents an analytical design approach for a proposed three-stage charge pump (CP), focusing on achieving optimal balance among efficiency, output ripple, Icc, and minimal capacitor. The proposed 28 nm three-stage CP requires 1.8 V IO devices for 3.35 V output voltage and achieves 46.5% voltage conversion ratio (VCR). It includes a ripple reduction stage to ensure a ripple below 6mV with high current demands of up to 200 μ A, without an additional space for over-voltage protection within the CP core. Corners and Monte Carlo simulations are conducted to validate the robustness of the design. By eliminating HV-transistors or multi-phase clocks, the design effectively reduces system costs, enhancing the efficiency and scalability of emerging neuromorphic systems.Publicationtype: Conference Paper37 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Automatic length measurements in hexapod fixators using optical proximity sensorsHexapod fixators are a specialized type of external fixators, which are used in the treatment of complex bone fractures. A set of metallic rings, which are attached to the bone fragments using wires and which are connected to each other by six length-adjustable struts, so-called distractors, enables a flexible and precise repositioning of fractures in six degrees of freedom. The lengths of the distractors define the configuration of the hexapod fixator and typically have to be iteratively adjusted over a period of several weeks. However, since the distractors are hard to reach for the patients, the length control is error-prone, limits the patient’s autonomy and can even require prolonged hospitalization. To overcome these limitations, a new system for automatically measuring the distractor lengths is proposed, which utilizes optical proximity sensors and wirelessly transmits the results to a reader device. The system achieves a measurement accuracy of less than 1 mm over the full measurement range of 105 mm. It can be powered autonomously from a small button cell for several weeks. With dimensions of 24 mm x 10 mm, the electronics module adds only little volume and weight.Publicationtype: Conference Paper41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Challenges and Opportunities Applying Laser Beam Scanning Displays Based on Biaxial Resonantly Operated MEMS Scanners(2024-10); 54 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Rapid prototyping of molds for the encapsulation of electronic implants using additive manufacturing(Infinite Science Publishing, 2024-09-09); ; ; ; Designing encapsulations for medical implants with integrated electronics is very challenging because a solution for several different and partly opposing requirements like biocompatibility, low water permeability, mechanical stability and small dimensions has to be found. This work focusses on epoxy encapsulations, which are conventionally cast using silicone molds. For making these molds, a pattern has to be CNC machined and the silicone mold has to be cast from it. In this paper, a rapid prototyping method is proposed, which uses additively manufactured molds made by an inkjet 3D printer that operates with a silicone-based material. A proof of concept is presented for an electronic osteosynthesis implant, which is successfully encapsulated following the rapid prototyping method and compared to results obtained with the conventional method. The demonstrator was immersed in isotonic saline solution for three weeks without any negative effects on the functionality. The rapid prototyping approach required only 15% of the time needed by the conventional mold making process based on silicone casting and used less material. This shortens design cycles for the optimization of the encapsulation for electronic implants and enables to evaluate more design variations with little additional effort. Moreover, designs with more degrees of freedom are available in the additive manufacturing process. For casting the encapsulation, the same material as for the final implant can be used so that many properties like water permeability and mechanical stability can be evaluated in the early development phase.Publicationtype: Journal Article44 22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Evaluation of On-the-fly Scanning Effects on Complex Field Retrieval Using a Single Probe(2024-09); ; The on-the-fly (OTF) scanning method has become a popular technique for rapidly characterizing electromagnetic (EM) near-fields. A recent advancement in OTF methods enables high-resolution retrieval of complex fields using a single probe. This work investigates the scanning effects occurring in combination with this technique. Firstly, Faraday's law of induction is employed to study the behavior of moving conductors in dynamic EM fields. Theoretical analysis reveals three distinct dependencies of the probe signal: frequency, probe movement, and the spatial distribution of the complex field. Subsequently, the scanning effects are numerically evaluated on a realistic microstrip line (MSL) structure exhibiting a dynamic field variation exceeding 70 dB. The results demonstrate that OTF scanning can achieve an accuracy surpassing 99.9% at any scanning speed below 10 m/s across the kHz to GHz range. In this regime, the primary source of OTF measurement error is the field magnitude distribution, which is largely independent of frequency. Finally, the MSL is measured at 100 MHz using a near-field scanner based on an industry robot with a maximum movement speed of 0.36 m/s. Compared to the OTF scanning effects, position tracing errors and signal acquisition accuracy have a more significant influence on the measurement. This highlights the efficiency and practical applicability of the single probe OTF scanning technique.Publicationtype: Conference Paper17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 3.35V High Voltage Electroforming Generator in 28nm with 5.3mV ripple and 46% efficiency for HfO₂-based Memristors(IEEE, 2024-07); ; A high voltage (HV) that is usually not available in modern nodes is required to form memristors. A scalable implementation requires the HV to be generated on chip and this work proposes such a generator. In a 28 nm CMOS process, a three-stage charge pump (CP)) is designed in the absence of HV transistors. For the HfO2 based memristor electroforming (EF), a developed CP runs with an efficiency of 46.5% at an output voltage of 3.35 V and a load current of 184.9 μ A from a 1.8 V supply. The optimum design strategy for a cross-coupled charge pump (CC-CP) is explained for a low ripple <6 mV, while at the same time ensuring lower capacitor value and high reliability. The results of an over-voltage analytical investigation have important ramifications for lowering the overall area without compromising output voltage or CP efficiency. Monte Carlo simulation for 200 samples were also performed to verify the design's robustness. However, the proposed design can be readily extended to any memristor application or material, thereby paving the way for the integration of fully integrated chips (ICs) for memristor EF in smaller technology nodes.Publicationtype: Conference Paper26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Magnetoelastic constraint on sensor-intrinsic noise(IEEE, 2024-05); ; ; ; Intrinsic magnetic noise limits the functionality of most magnetic field sensors. This study investigates the impact of intrinsic magnetic noise on the performance of magnetoelectric magnetic field sensors, at the example of two sensor concepts based on the ΔE effect and the converse magneto electric effect, respectively. Our analysis shows that they exhibit comparable behavior in terms of noise and operational limitations. In both cases, the magnetic properties of the magnetostrictive layer determine the theoretical minimum of the equivalent magnetic noise density. The range of operational parameters with which this minimum can be achieved is constrained by the magnetic noise source linked to the nonlinearity of the magnetostrictive properties. This previously unidentified noise source significantly degrades sensor performance and imposes a strict limit on the acceptable noise level of the nonmagnetic noise sources in the sensor system. Although this noise source is particularly evident in highly magnetostrictive materials, it can be relevant to a wide range of devices incorporating magnetic materials.Publicationtype: Conference Paper27