Robert Puers

KU Leuven | ku leuven · Department of Electrical Engineering (ESAT)

Detecting a variety of biological samples accurately and swiftly in an integrated way is of great practical significance. Currently, biofluorescent spectrum detection still largely relies on microscopic spectrometers. In this study, we propose an integrable method to detect biofluorescent spectrums with designed liquid crystal tunable filter (LCTF)...

This paper presents the design and fabrication method to render a silicon-on-insulator (SOI)-based pMUT array bendable. The proposed method can be applied to silicon-based pMUT arrays with different acoustical specifications. A bendable array based on the proposed method is highly conformal to the target structure. The bendable structure is made ou...

Objectives To test the hypothesis that an implantable sensing system containing accelerometers can detect small‐scale autonomous movements, also termed micromotions, which might be relevant to bladder physiology. Methods We developed a 6‐mm submucosal implant containing a pressure sensor (MS5637) and a triaxial accelerometer (BMA280). Sensor proto...

This paper presents a novel fabrication process that allows integration of polydimethylsiloxane (PDMS)-based microfluidic channels and metal electrodes on a wafer with a micrometer-range alignment accuracy. This high level of alignment accuracy enables integration of microwave and microfluidic technologies, and furthermore accurate microwave dielec...

When screening microbial populations or consortia for interesting cells, their selective retrieval for further study can be of great interest. To this end, traditional fluorescence activated cell sorting (FACS) and optical tweezers (OT) enabled methods have typically been used. However, the former, although allowing cell sorting, fails to track dyn...

The detection and analysis of circulating tumor cells (CTCs) plays a crucial role in clinical practice. However, the heterogeneity and rarity of CTCs make their capture and separation from peripheral blood very difficult while maintaining their structural integrity and viability. We previously demonstrated the effectiveness of the Magnetic Cell Cen...

Objective: Long-term electrophysiological recordings of neural activity in freely behaving animals are indispensable to advance the understanding of complex brain function. It is a technical challenge to chronically monitor the detailed activity across multiple distributed brain regions in freely behaving animals over a period of months. Here we p...

Traditional urodynamics have poor correlation with urological symptoms. Ambulatory urodynamics may improve this correlation but the need for a transurethral catheter and the time-consuming nature of this examination limits its use. Therefore, the objective of this study was to develop a wireless real-time bladder pressure measurement device for rep...

This paper presents the design, fabrication, and characterization of a pMUT array to be used in underwater sensor networks. A 1 μm Lead Zirconate Titanate (PZT) layer was used as the piezoelectric material. The array consists of 8x8 pMUT elements with a diameter of 410 μm and Si thickness of 6 μm. The fabricated array generates 1360 Pa/V @ 1 cm und...

Unobtrusive monitoring of drivers’ physiological parameters is a topic gaining interest, potentially allowing to improve the performance of safety systems to prevent accidents, as well as to improve the driver’s experience or provide health-related services. In this article, two unobtrusive sensing techniques are evaluated: capacitively coupled sen...

Vitamin B-12 (cobalamin) deficiency in humans is a worldwide problem emanating from varied causes such as insufficient dietary intake or malabsorption of the micronutrient due to an underlying condition (absence or failure of intrinsic factor, atrophic gastritis, post-operative bariatric surgery, inflammatory bowel disease, cobalt deficiency etc.)....

Capacitively-coupled ECG (ccECG) and bioimpedance (ccBIOZ) measurements are highly sensitive to motion artefacts. This limits their use in real-life situations. This work presents an array-based system for the simultaneous acquisition of ccECG and ccBIOZ, together with a quality-based electrode scanning approach for ccECG. This allows to increase t...

This article gives a condensed review of the MEMS actuators that have seen light in the past three decades. Since the electrostatic drive comes almost natural when creating mechanical devices with the available MEMS technology, greater importance is highlighted. Nevertheless, by introducing more non-IC related materials, other devices are presented...

This protocol provides information for the invasive urodynamic measurement of bladder pressure, by urethral catheter as well as wireless device (bladder pill).

In this paper, a miniaturized microwave resonator is designed and fabricated. A loop mode resonance is created when the permittivity difference of the two materials loaded in the two fluidic channels are sufficiently large. A highly concentrated electrical field is generated in a microfluidic channel loaded with deionized water to achieve high sens...

This paper presents the design and fabrication process of a spherical-omnidirectional ultrasound transducer for underwater sensor network applications. The transducer is based on the vibration of two hemispheres with a thickness of 1 mm and an outer diameter of 10 mm, which are actuated by two piezoelectric ring elements. Since the ultrasound wave...

Polymer microneedles that get resorbed after insertion in the body have several interesting applications, for example in the insertion of ultra-flexible electrode arrays in neural tissue. In this work, we explore the use of molds created by etching in (3 1 1) silicon as a basis for the fabrication of such microneedles. Such molds can be etched anis...

In the quest for chronically reliable and bio-tolerable brain interfaces there has been a steady evolution towards the use of highly flexible, polymer-based electrode arrays. The reduced mechanical mismatch between implant and brain tissue has shown to reduce the evoked immune response, which in turn has a positive effect on signal stability and no...

iNtroductioN: the increasing popularity of inertial sensors in clinical practice is not supported by precise information on their reliability or guidelines for their use in rehabilitation. the authors investigated the state of the literature concerning the use of inertial sensors for gait analysis in both healthy and pathological adults comparing t...

Achieving a stable, long-term connection with millions of neurons within living organisms remains one of the dreams of neuroscience. Silicon shank based probes lead the field in terms of pure channel count. On the other hand, polymer neural probes offer superior biocompatibility, ruggedness and lower cost. This work tries to merge these technologie...

A miniature sensor and control system is developed to facilitate human eye ciliary muscle movement detection and to drive the corresponding liquid crystal based lens to create an autofocusing lens for cataract patients. The movement of the ciliary muscle is detected by a marker that detunes a Colpitts oscillator. The change in oscillation frequency...

We report the design and implementation of a unique, wafer sized stretchable and bendable monolithic silicon matrix structure. The achieved stretchability allows for simultaneous omnidirectional folding, required to conform the structure to complex curved 3D surfaces. Moreover, it also enables dynamic mechanical deformation of the structure to cope...

Ultra-flexible electrode arrays with a cross-sectional area of only a few μm² show great promise for long-term, high resolution neural interfacing without detrimental scar tissue formation. However, due to their low stiffness, insertion is a challenge. In this work, we investigate microneedles consisting of quickly biodegradable, short-chained, aci...

This paper presents an optimized way of lead zirconate titanate (PZT) deposition in orderto selectively grow three different (100/001), (110), and (111) crystal orientation in two differentthickness ranges, thinner and thicker than 400 nm. The thickness of the PZT layer is also optimizedto not diminish the generated bending moment more than 10%. A...

In recent years, Teflon-on-glass microwells have been successfully implemented in bead-based digital bioassays for the sensitive detection of single target molecules. Their hydrophilic-in-hydrophobic (HIH) nature enables the isolation and analysis of individual beads, carrying the target molecules, which can be further manipulated accurately throug...

A simplified dielectric material characterization technique that combines an equivalent impedance algorithm and a general “line–line” trace method is introduced. The technique is applicable to every type of transmission lines. Due to the convenient fabrication and the allowance of integration with various polymers, coplanar waveguide transmission l...

Requiring neither labels nor complicated data processing technique, electrical techniques are very attractive and promising in biological/pharmaceutical research. Traditionally, impedance spectroscopy in the kHz frequency range is used for measuring cell growth and other dynamic cell culture responses. This paper reports, for the first time, real-t...

We report the design and implementation of a unique, wafer sized stretchable and bendable monolithic silicon matrix structure. The achieved stretchability not only allows for one directional folding, but is capable of bending in two directions simultaneously, which is required to conform the structure to complex shapes such as spheres, tori, hyperb...

Detection methods that do not rely on the amplification of DNA but can reach sensitivity, specificity and throughput of gold standard methods, such as qPCR, have been extensively explored in recent years. Here, we present a hydrophilic-in-hydrophobic (HIH)-microwell array platform that empowers a panel of different amplification-free DNA bioassays:...

This paper investigates the effects on the blood compatibility of surface nanostructuring of Parylene-C coating. The proposed technique, based on the consecutive use of O₂ and SF₆ plasma, alters the surface roughness and enhances the intrinsic hydrophobicity of Parylene-C. The degree of hydrophobicity of the prepared surface can be precisely contro...

Objective: This study describes the design and microfabrication of a foldable thin-film neural implant and investigates its suitability for electrical recording of deep-lying brain cavity walls. Approach. A new type of foldable neural electrode array is presented, which can be inserted through a cannula. The microfabricated electrode is specifica...

Sleep-related conditions require high-cost and low-comfort diagnosis at the hospital during one night or longer. To overcome this situation, this work aims to evaluate an unobtrusive monitoring technique for sleep apnea. This paper presents, for the first time, the evaluation of contactless capacitively-coupled electrocardiography (ccECG) signals f...

This paper describes a unique technique to manufacture highly stretchable and implantable interconnects. A possible application is presented, where the interconnects are intended to create a network of nodes sensing biological parameters in e.g. the bladder wall. The interconnects are fabricated by embedding nickel-plated carbon fibres bundles firs...

This paper proposes a novel packaging solution which integrates micro-machined 3D horn antennas with millimeter-wave and THz tranceivers. This packaging solution is shown to be a valid competitor to existing technologies like metallic split-block waveguides and low temperature cofired ceramics. Three different fabrication methods based on two-photo...

In this paper we report on the use of dextran as a temporary, fast dissolving stiff coating for flexible neural probes. Although polymer-based neural implants offer several advantages, compared to their rigid silicon counterparts, they pose significant challenges during implantation. Due to their extreme flexibility, they have the tendency to buckl...

We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated i...

Showcasing the fabrication and characterization of micrometer sized, 3D porous Pt monoliths via atomic layer deposition on Zeotile-4 mesoporous silica by a team of researchers from the Belgian universities KU Leuven, University of Antwerp, and University of Gent. The exceptionally 3D porous platinum structure consists of robust and easy to handle...

A semi-flexible polymer microtensiometer for local surface pressure measurements of Langmuir monolayers is presented. The current device geometry and read-out method via image analysis result in a theoretical accuracy of ±0.02mN⋅m(-1) for a dynamic range between 0 and 75mN⋅m(-1). The tensiometer sensitivity and dynamic range are easily tunable as t...

This paper presents an array of five aluminum nitride (AlN) based piezoelectric micromachined ultrasound transducers (pMUTs) with different dimensions operating at 540–2360 kHz in air. Due to the damping effect of water or oil on the vibration of each individual pMUT, their frequency response tends to merge and significantly increases the bandwidth...

An implantable sensor system has been developed to explore the physiological behaviour of the bladder wall. It consists of a 3-axis digital accelerometer and a pressure sensor on the upper side of a flexible polyimide printed circuit board. On the bottom side, two metallic hooks prevent migration of the device in the bladder wall while simultaneous...

The design and implementation of a medical implantable device for bladder monitoring is presented. A network of accelerometers is to be implanted in-between the outside bladder muscle and the mucous membrane. A pressure sensor is also implanted in this submucosal layer to obtain intraluminal pressure readings. The sensor system is powered by an imp...

A robust and easy to handle 3D porous platinum structure was created via replicating the 3D channel system of an ordered mesoporous silica material using atomic layer deposition (ALD) over micrometer distances. After ALD of Pt in the silica material, the host template was digested using hydrogen fluoride (HF). A fully connected ordered Pt nanostruc...

Acceleration signals, collected from the inner and the outer heart wall, offer a mean of assessing cardiac function during surgery. Accelerometric measurements can also provide detailed insights into myocardial motion during exploratory investigations. Two different implantable accelerometers to respectively record endocardial and epicardial vibrat...

A robust and low cost ionic liquid based strain sensor is fabricated for high strain measurements in biomedical applications (up to 40 % and higher). A tubular 5 mm long silicone microchannel with an inner diameter of 310 µm and an outer diameter of 650 µm is filled with an ionic liquid. Three ionic liquids have been investigated: 1-butyl-1-methylp...

Objective: This study investigates the suitability of a thin sheet of extracellular matrix (ECM) proteins as a resorbable coating for temporarily reinforcing fragile or ultra-low stiffness thin-film neural implants to be placed on the brain, i.e. microelectrocorticographic (µECOG) implants. Approach: Thin-film polyimide-based electrode arrays we...

Monitoring elite athletes in real-time remains challenging. A lot of research has been conducted towards the application of inertial measurement systems for the quantification of performance in sports applications. The challenge however, remains in creating systems that meet high comfort standards in order to be able to apply them on a daily basis....

An implantable accelerometer has been developed to monitor the cardiac function and the heart wall motion. The device, to be stitched on the pericardium, can also provide an insight on amplitude and frequency components of the acceleration on different locations on the heart. A commercially available three-axis accelerometer was mounted on a miniat...

We report a novel process that allows depositing hierarchically porous platinum, i.e. platinum with structured pores from about 1 micron down to 3 nm in porosity, in situ on flexible microelectrodes. The process is based on molecular self-assembly of a porous silica zeotile, which is then deposited on the electrode contacts of flexible platinum ele...

This work presents progress on development of the “Bladder pill”, a pressure monitoring implant for urological diagnosis. The device, measuring as little as 5x30 mm, uses resonant inductive coupling for wireless powering and communication via an omnidirectional “3-D” receiving coil. The transmitting coil along with the battery-powered control and d...

In this work a new type of foldable neural electrode is presented. The microfabricated electrode is specifically designed for Deep Brain Stimulation of the cavity wall of thalamic lesions resulting from brain infarcts. On implantation, the electrode is introduced through a cannula, after which the flower-like structure unfolds, contacting the cavit...

This paper presents silicon nitride (SixNy) photonic integrated circuits (PICs) with high performance at a wavelength of 450 nm, which, therefore, is suitable for neuronal stimulation with optogenetics. These PICs consist of straight and bent waveguides, and grating couplers that are fabricated in a complementary metal-oxide-semiconductor (CMOS)-co...

A three step Deep Reactive Ion Etch (DRIE) process is developed to etch trenches of 10μm wide to a depth of 130μm into silicon with an etch rate of 2.5μm min⁻¹. The aim of this process is to obtain sidewalls with an angle close to 90°. The process allows the etching of multiple trenches with high aspect ratios that are closely placed together. A th...

Aluminum nitride (AlN) thin film was grown by plasma enhanced atomic layer deposition using trimethylaluminum and ammonia precursors. A method was found to have crystalline thin film AlN with almost zero thickness variation and a truly one layer deposition of atoms per each cycle of the process. The growth rate saturated at ~ 1 Å/cycle, and the thi...

We present a high density CMOS neural probe with active electrodes (pixels), consisting of dedicated in-situ circuits for signal source amplification. The complete probe contains 1356 neuron sized (20×20 μm²) pixels densely packed on a 50 μm thick, 100 μm wide and 8 mm long shank. It allows simultaneous high-performance recording from 67...

Monolithic solar water splitting devices consist of photovoltaic materials integrated with electrocatalysts and produce solar hydrogen by water splitting upon solar illumination in one device. Upscaling of monolithic solar water splitting devices is obstructed by high ohmic losses in the electrolyte due to long ionic transport distances. A new desi...

This work explores the benefits of linear-mode avalanche photodiodes (APDs) in high-speed CMOS imaging as compared to different approaches present in literature. Analysis of APDs biased below their breakdown voltage employed in single-photon counting mode is also discussed, showing a potentially interesting alternative to existing Geiger-mode APDs....

The aim of this study is to investigate the intravascular application of a micro-electro-mechanical system (MEMS) pressure sensor to directly measure the hemodynamic characteristics of a ventricular assist device (VAD). A bio- and hemo-compatible packaging strategy is implemented, based on a ceramic thick film process. A commercial sub-millimeter p...

In this paper, we investigate the possibilities of using water droplets to support and move a platform, making use of the principle of electrowetting. A new way for making micro-conveyors is thereby developed. The most important element in designing such a micro-conveyor system is the load that it can carry. This paper focuses on the static part, a...

A compact wireless power and communication development system for implantable devices was designed and tested with two receiver circuits based on a 433 MHz separate RF link and a uni-directional near-field communication link that uses the powering field. The power transmitter was designed around a Royer oscillator with additional hardware for power...

The detection of single molecules in magnetic microbead microwell array formats revolutionized the development of digital bio-assays. However, retrieval of individual magnetic beads from these arrays has not been realized until now despite having great potential for studying captured targets at the individual level. In this paper, optical tweezers...

A system was designed to acquire experimental data from custom sensors in a conventional operating room. Available clinical equipment is usually incapable of reading out such experimental sensor systems and/or handling the resulting data stream. The proposed system integrates these prototype sensors and provides a data-alignment method based on ECG...

A robust wireless system for capacitive ECG is presented, which measures electrode-body capacitive impedance, acceleration, and gyroscope signals from the electrodes to be used in motion artifact reduction algorithms. The system dynamically adapts its robustness and signal quality according to the environmental conditions. Optimizations including b...

Noise performance of avalanche photodiodes in light detection is typically described by the excessive noise factor, taking into account only the increase of the variance of the output electron count distribution with respect to the input. This approach is attractive since the excessive noise factor, to