Research Interests:
A 3D-packaging technology is developed which focuses on stacking and interconnecting multiple thinned dies, in order to obtain a functional multi-chip package within the volume of single standard-thickness die. This can be achieved by... more
A 3D-packaging technology is developed which focuses on stacking and interconnecting multiple thinned dies, in order to obtain a functional multi-chip package within the volume of single standard-thickness die. This can be achieved by laminating multiple layers of spin-on polyimide based ultrathin chip packages (UTCPs). The use of thin-film technology allows realizing multiple fan-outs with a fine pitch, interconnected with through-hole vias. This novel 3D integration technology has a broad range of industrial and medical electronic applications.
Research Interests:
Research Interests:
Research Interests:
Research Interests: Polymer and Nucleation
Research Interests:
ABSTRACT We developed a miniaturized pump (8 mm diameter, 1 mm thickness) which generates a flow rate of 2 μL/min at a pressure of 3 MPa. It consists of a stack of several conductive polymer (CP) layers intercalated with electrolyte... more
ABSTRACT We developed a miniaturized pump (8 mm diameter, 1 mm thickness) which generates a flow rate of 2 μL/min at a pressure of 3 MPa. It consists of a stack of several conductive polymer (CP) layers intercalated with electrolyte layers. The stack is housed in a polycarbonate case specially conceived for integration in a lab-on-chip device. The actuator operates at a bias lower than 2V. A maximum strain of 13% is measured in the single CP layer when it expands against atmospheric pressure; this strain is reduced by only a factor of 3 when pressure increases to 15 MPa. Using the stacked actuator, a maximum strain of 5% is measured.
Research Interests: Materials Science, Microfluidics, Chip, Actuator, Strain, and 3 moreDevices, Fluidics, and Polycarbonate
Research Interests:
Research Interests:
Barrier layers for the long-term encapsulation of implantable medical devices play a crucial role in the devices’ performance and reliability. Typically, to understand the stability and predict the lifetime of barriers (therefore, the... more
Barrier layers for the long-term encapsulation of implantable medical devices play a crucial role in the devices’ performance and reliability. Typically, to understand the stability and predict the lifetime of barriers (therefore, the implantable devices), the device is subjected to accelerated testing at higher temperatures compared to its service parameters. Nevertheless, at high temperatures, reaction and degradation mechanisms might be different, resulting in false accelerated test results. In this study, the maximum valid temperatures for the accelerated testing of two barrier layers were investigated: atomic layer deposited (ALD) Al2O3 and stacked ALD HfO2/Al2O3/HfO2, hereinafter referred to as ALD-3. The in-house developed standard barrier performance test is based on continuous electrical resistance monitoring and microscopic inspection of Cu patterns covered with the barrier and immersed in phosphate buffered saline (PBS) at temperatures up to 95 °C. The results demonstrate...
Research Interests:
Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging... more
Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO2/Al2O3/HfO2 (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further...
Research Interests:
Research Interests:
Tuning the electrode impedance through the DC biasing of iridium oxide is presented. Impedance reduction of up to two orders of magnitude was reproducibly observed in 20 microm diameter microelectrodes at a biasing of 1V.
Research Interests:
ABSTRACT A Lab-on-Chip system is proposed, capable of SNP (Single Nucleotide Polymorphism) detection in DNA. One of the core components is an advanced filter consisting of an ordered array of Si micro-pillars enabling fast and effective... more
ABSTRACT A Lab-on-Chip system is proposed, capable of SNP (Single Nucleotide Polymorphism) detection in DNA. One of the core components is an advanced filter consisting of an ordered array of Si micro-pillars enabling fast and effective separation of 5 DNA segments with different length using chromatographic techniques. Also a dedicated micro-pump is fabricated based on conductive polymer actuation, generating the required high pressure to sustain the fluid flow through the total system. For the detector, a known detector principle is applied, but pronounced miniaturization is carried out in order to make a small and portable system.
Research Interests:
Research Interests: Computer Science, Materials Science, Electroencephalography, Medicine, Electrocardiography, and 12 moreCoating, Fabrication, Surface Properties, Reproducibility of Results, Electrodes, Sensitivity and Specificity, Electrode, Equipment Design, Equipment Failure Analysis, Electric Impedance, Needles, and Electrical Impedance
Research Interests:
Research Interests:
Dry electrodes are attractive for biopotential recordings to avoid the drawbacks related to wet gel electrodes. Commercially available EEG systems with hard metal-based dry electrodes are uncomfortable and even painful. Two types of... more
Dry electrodes are attractive for biopotential recordings to avoid the drawbacks related to wet gel electrodes. Commercially available EEG systems with hard metal-based dry electrodes are uncomfortable and even painful. Two types of polymer-based dry electrodes for higher user comfort are presented. Our dry electrodes are compared with wet gel electrodes regarding impedance, and EEG & ECG recording. Very promising results are obtained for ECG and EEG, resp. without and with pre-amplification.status: accepte
Research Interests:
Research Interests:
In this paper we describe the successful integration of 50nm half pitch single damascene copper trenches in BD II (k=2.5) low-k dielectric on 300mm wafers, focusing on integration issues encountered during development.
Research Interests:
KULeuven. ...
Research Interests:
We have studied the effect of nanopillar patterning on the saturation magnetization of the CoFeB free layer in MgO magnetic tunnel junctions. Before patterning, the free layer magnetization is measured by ferromagnetic resonance and is... more
We have studied the effect of nanopillar patterning on the saturation magnetization of the CoFeB free layer in MgO magnetic tunnel junctions. Before patterning, the free layer magnetization is measured by ferromagnetic resonance and is found to be close to the bulk value, with no detectable interface anisotropy. After patterning, the shape anisotropy and the frequency of the main spin wave mode indicate that the free layer magnetization is substantially reduced. Current dependent measurements indicate that this is not due to Joule heating. Size dependent measurements indicate that the magnetization reduction most likely arises from process damage during the etching step.
Research Interests:
We demonstrate spin-torque induced coherent auto-oscillation in magnetic tunnel junctions of composition PtMn/CoFe/Ru/CoFeB/MgO/CoFeB and of low resistance-area product. At the generation threshold, we observe a strong line narrowing down... more
We demonstrate spin-torque induced coherent auto-oscillation in magnetic tunnel junctions of composition PtMn/CoFe/Ru/CoFeB/MgO/CoFeB and of low resistance-area product. At the generation threshold, we observe a strong line narrowing down to 6 MHz at 300 K and a dramatic increase in oscillator power, yielding spectrally pure oscillations with extremely low flicker noise. The induced auto-oscillations are observed even at zero applied field. The frequency of the oscillation mode, and its dependence with easy and hard axis fields are consistent with an acoustical excitation of the two layers of the synthetic ferrimagnet subsystem. Setting the synthetic ferrimagnet into auto-oscillation requires the current polarity that transfers electrons from the synthetic ferrimagnet to the free layer. In auto-oscillation mode, line jitter is observed such that it is the line envelope that is measured in most cases. The line properties for applied fields near the instability boundaries of the Stone...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Conventional ECG and EEG gel electrodes are widely used in health care applications. These electrodes deliver high-quality signals due to their low impedance, but they have important drawbacks, such as time-consuming electrode set-up for... more
Conventional ECG and EEG gel electrodes are widely used in health care applications. These electrodes deliver high-quality signals due to their low impedance, but they have important drawbacks, such as time-consuming electrode set-up for EEG followed by a painful removal, skin irritation by the gel, signal degradation due to drying of the gel, etc. To solve this, various types of dry electrodes attract attention last years. Hard metal dry electrodes show low impedance, but most are not comfortable for the patient. Flexible polymer-based electrodes are presented in this work to avoid the disadvantages of gel electrodes while significantly improving user comfort. Different additives are mixed in these polymers and optimized to improve various relevant properties. An important electrode property is low impedance, which directly affects signal quality and influences the sensitivity to motion artifacts. The polymer composition influences also the mechanical properties, as well as the material flow during molding and hence the electrode fabrication yield. Moreover, various electrode shapes are tested to achieve appropriate mechanical properties and increase user comfort. For ECG & EEG applications, the best performing dry electrodes are selected and results are compared with wet electrode signals .
Research Interests:
Research Interests:
Research Interests:
Within our internal FITEP technology platform (FITEP: Flexible Implantable Thin Electronic Package), a novel implantable packaging technology is under development in order to realize a very small, flexible, biomimetic package for... more
Within our internal FITEP technology platform (FITEP: Flexible Implantable Thin Electronic Package), a novel implantable packaging technology is under development in order to realize a very small, flexible, biomimetic package for electronic implants. This new platform enables a radical miniaturization of the final implanted device, which opens many new possibilities for the medical world, since it will be possible to insert electronic sensors in very small locations, such as arteries, nerves, glands,... The device encapsulation consists of a multilayer of biocompatible polymers and ultrathin ceramic diffusion barriers deposited using ALD techniques (ALD: atomic layer deposition) in order to fabricate a very thin and flexible but also highly hermetic device packaging. Concerning the selection of biocompatible polymers, polyimide can offer a profound mechanical support for the various device components, while Parylene with its excellent step coverage creates a highly conformal coating...
Research Interests:
Research Interests:
Research Interests:
Detailed testing has shown that active dry electrodes made from conductive polymers can be applied for user-friendly, high quality EEG recordings. Using a dedicated elastic interconnect technique, the dry electrodes can be integrated in a... more
Detailed testing has shown that active dry electrodes made from conductive polymers can be applied for user-friendly, high quality EEG recordings. Using a dedicated elastic interconnect technique, the dry electrodes can be integrated in a headset ensuring good skin contact. Combined with an elegant headset design, a promising solution is offered for user-friendly EEG monitoring outside the hospital.
Research Interests:
Several requirements exist for medical devices for long term implantation. Firstly, the foreign body reaction and/or inflammation occurring upon implantation should remain mild and short in time. Moreover, the device needs to be... more
Several requirements exist for medical devices for long term implantation. Firstly, the foreign body reaction and/or inflammation occurring upon implantation should remain mild and short in time. Moreover, the device needs to be biocompatible during the total implantation duration, hence not causing reactions which decrease the patient’s health. Finally, the device needs to work properly and safe during the total period of implantation, not suffering from corrosion or chemical degradation. To meet these requirements, diffusion of body fluids into the package should be avoided as well as diffusion of toxic device materials into the body, hence a hermetic packaging method is an absolute necessity. Here, a flexible hermetic packaging is presented using alternating polyimide and atomic layer deposited (ALD) metal oxides. Good adhesion between the inorganic ALD layers and the polyimide is required to avoid the creation of lateral diffusion pads. To obtain this, surface modifications of b...
Research Interests:
Polyimide is commonly used for packaging of medical devices due to its thermal and chemical stability, mechanical strength and flexibility and low moisture absorption [1]. Although it is known to be biocompatible [2], a cold plasma... more
Polyimide is commonly used for packaging of medical devices due to its thermal and chemical stability, mechanical strength and flexibility and low moisture absorption [1]. Although it is known to be biocompatible [2], a cold plasma treatment has been applied for the activation of BPDA-PPD polyimide in order to enhance the interaction and integration of the device with the surrounding tissue to minimize the foreign body reaction after implantation. The influence of different parameters of the plasma activation on the surface composition of polyimide has been studied (exposure time, discharge power, plasma gas) as well as the hydrophobic recovery of optimal treatments over the 24 h following the exposure. For all gases (air, He, N2, Ar) short treatment times (1.0-32.0 s) and low discharge powers (1.5-3.0 W) revealed to be enough to introduce oxygen-containing functional groups, with an increase of 40-70% in the O/C ratio. Hydrophobic recovery stabilized fast (2.0-4.0 h after exposure)...
Research Interests:
Taking EEG out of the traditional, clinical environment into people’s homes will require a paradigm shift, in which a set of technological challenges needs to be tackeled, from electrodes and analog readout to application and headset... more
Taking EEG out of the traditional, clinical environment into people’s homes will require a paradigm shift, in which a set of technological challenges needs to be tackeled, from electrodes and analog readout to application and headset design. In this work, the challenges associated to the electronical and mechanical aspects of a wearable EEG acquisition unit are summarized.
Research Interests:
Our biocompatible packaging concept for implantable electronic systems combines biocompatibility, hermeticity and extreme miniaturization. In a first phase, all chips are encapsulated in order to realize a bi-directional diffusion barrier... more
Our biocompatible packaging concept for implantable electronic systems combines biocompatibility, hermeticity and extreme miniaturization. In a first phase, all chips are encapsulated in order to realize a bi-directional diffusion barrier preventing body fluids to leach into the package causing corrosion, and preventing IC materials such as Cu to diffuse into the body, causing various adverse effects. Various clean room materials are tested with respect to their suitability as encapsulation material. In a second phase of the packaging process, all chips of the final device should be electrically connected, applying a biocompatible metallization scheme using eg. gold or platinum. Device assembly is the final packaging step, during which all system components will be interconnected. To provide sufficient mechanical support, all these components are embedded using a biocompatible elastomer such as PDMS.
Research Interests:
There is an increasing interest in atomic layer deposition (ALD) on polymers for the development of membranes, electronics, (3D) nanostructures and specially for the development of hermetic packaging of the new generation of flexible... more
There is an increasing interest in atomic layer deposition (ALD) on polymers for the development of membranes, electronics, (3D) nanostructures and specially for the development of hermetic packaging of the new generation of flexible implantable micro-devices. This evolution demands a better understanding of the ALD nucleation process on polymers, which has not been reported in a visual way. Herein, a visual study of ALD nucleation on polymers is presented, based on the different dry etching speeds between polymers (fast) and metal oxides (slow). An etching process removes the polyimide with the nucleating ALD acting as a mask, making the nucleation features visible through secondary electron microscopy analyses. The nucleation of both Al2O3 and HfO2 on polyimide was investigated. Both materials followed an island-coalescence nucleation. First, local islands formed, progressively coalescing into filaments, which connected and formed meshes. These meshes evolved into porous layers th...
Research Interests:
Advanced bionic prosthetics that can restore both the motor functionality and sensory perception of an amputee, require high-resolution recording and stimulation interfaces targeting the peripheral nervous system (PNS). To provide high... more
Advanced bionic prosthetics that can restore both the motor functionality and sensory perception of an amputee, require high-resolution recording and stimulation interfaces targeting the peripheral nervous system (PNS). To provide high nerve fiber selectivity, we propose a low-noise (3.67μVrms) low-power (2.24mW) and high-density CMOS microelectrode probe for intra-neural implantation. The probe is composed of two ICs, encapsulated in a biocompatible and hermetic package, each featuring 64 recording and 16 stimulation electrodes. A backend IC digitizes the recorded signals at 31.25kS/s and provides spike detection.
Research Interests:
Objective. In this work, the development of an active high-density transverse intrafascicular micro-electrode (hd-TIME) probe to interface with the peripheral nervous system is presented. Approach. The TIME approach is combined with an... more
Objective. In this work, the development of an active high-density transverse intrafascicular micro-electrode (hd-TIME) probe to interface with the peripheral nervous system is presented. Approach. The TIME approach is combined with an active probe chip, resulting in improved selectivity and excellent signal-to-noise ratio. The integrated multiplexing capabilities reduce the number of external electrical connections and facilitate the positioning of the probe during implantation, as the most interesting electrodes of the electrode array can be selected after implantation. The probe chip is packaged using thin-film manufacturing techniques to allow for a minimally invasive electronic package. Special attention is paid to the miniaturization, the mechanical flexibility and the hermetic encapsulation of the device. Main results. A customized probe chip was designed and packaged using a flexible, implantable thin electronic package (FITEP) process platform. The platform is specifically developed for making slim, ultra-compliant, implantable complementary metal-oxide-semiconductor based electronic devices. Multilayer stacks of polyimide films and HfO2/Al2O3/HfO2 layers deposited via atomic layer deposition act as bidirectional diffusion barriers and are key to the hermetic encapsulation. Their efficacy was demonstrated both by water vapor transmission rate tests and accelerated immersion tests in phosphate buffered saline at 60 °C. Using the hd-TIME probe, an innovative implantation method is developed to prevent the fascicles from moving away when the epineurium is pierced. In addition, by transversally implanting the hd-TIME probe in the proximal sciatic nerve of a rat, selective activation within the nerve was demonstrated. Significance. The FITEP process platform can be applied to a broader range of integrated circuits and can be considered as an enabler for other biomedical applications.
Research Interests:
A biocompatible packaging process for implantable electronic systems is under development at imec, combining biocompatibility, hermeticity, extreme miniaturization and cost aspects. In a first phase of this packaging sequence, hermetic... more
A biocompatible packaging process for implantable electronic systems is under development at imec, combining biocompatibility, hermeticity, extreme miniaturization and cost aspects. In a first phase of this packaging sequence, hermetic chip sealing is performed by encapsulating all chips to realize a bi-directional diffusion barrier preventing body fluids to leach into the package causing corrosion, and preventing IC materials such as Cu to diffuse into the body, causing various adverse effects. For cost effectiveness, this chip sealing is performed as post-processing at wafer level, using modifications of standard clean room (CR) fabrication techniques. Well known conductive and insulating CR materials are investigated with respect to their biocompatibility, biostability, diffusion barrier properties and sensitivity to corrosion. Material selection and integration aspects are modified until good properties are obtained. In a second phase of the packaging process, all chips of the f...
Research Interests:
Research Interests:
A comfortable, wearable wireless ECG monitoring system is proposed. The device is realized using the combination of two proprietary advanced technologies for electronic packaging and interconnection : the UTCP (Ultra-Thin Chip Package)... more
A comfortable, wearable wireless ECG monitoring system is proposed. The device is realized using the combination of two proprietary advanced technologies for electronic packaging and interconnection : the UTCP (Ultra-Thin Chip Package) technology and the SMI (Stretchable Mould Interconnect) technology for elastic and stretchable circuits. Introduction of these technologies results in small fully functional devices, exhibiting a significant increase in user comfort compared to devices fabricated with more conventional packaging and interconnection technologies.