Martin Schuettler - Academia.edu (original) (raw)

Papers by Martin Schuettler

1st Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine and Biology. Proceedings (Cat. No.00EX451), 2000

In order to restore hand function in spinal cord injured people by functional electrical stimnlat... more In order to restore hand function in spinal cord injured people by functional electrical stimnlation of arm nerves, we developed an lllpolar neural cuff type electrode with integrated multiplexer circuit. This circuit reduces the number of necessary interconnection leads to a stimulator from twelve to four. Cable reduction was intended to reduce the risk of cable breakage which is one of the main reasons for implant failure. The multiplexer cuff electrode was fabricated applying a combination of micromacbining, hybrid integration and traditional silicone technology, which enabled one to make the system robust, mechanically flexible and small in size.

IFMBE Proceedings, 2009

ABSTRACT Neural interfaces are most commonly of electrical/electrochemical nature, employing meta... more ABSTRACT Neural interfaces are most commonly of electrical/electrochemical nature, employing metal electrodes that allow sensing of neural activity or stimulation of nerve cells by introduction of electrical currents. Some interfaces require additional ports for localized release of chemical agents, such as drugs that alter the behavior of the neural system, or dies that allow labeling of regions in the observed tissue for subsequent histological studies. In this paper we present a fabrication procedure for neural electrode arrays based on laser-ablation of medical grade silicone rubber and platinum foil, to which an additional laser-process is added in order to integrate fluidic channels into the silicone substrate. A variety of channels were produced having cross sectional areas ranging from approx. 40 · 80 µm2 to 130 · 170 µm2. In order to characterize the main fluidic properties of such channels, the pressure/flow rate ratio was measured and the burst pressure for two different channel geometries was determined. As a proof of concept, a prototype of a microfluidic nerve electrode was fabricated, having 4 metal electrodes and one fluidic channel that branches to each of the metal electrodes, ending in nozzles located at the rim of each electrode surface. The fluid dynamics were visualized by injecting died solvent into the channel inlet; a simultaneous escape of the fluid on each electrode site was observed.

Towards Practical Brain-Computer Interfaces, 2012

ABSTRACT

2007 3rd International IEEE/EMBS Conference on Neural Engineering, 2007

The electrode-tissue interface is of principal importance in neuroprosthesis. Indeed the successe... more The electrode-tissue interface is of principal importance in neuroprosthesis. Indeed the successes of the cochlear implant and other therapeutic devices are directly attributable to the design and fabrication techniques of their interfaces with neural tissue, that is, the electrode or electrode array. Traditional fabrication techniques are often labor-intensive and do not lend themselves to automation thereby increasing the cost of

2011 5th International IEEE/EMBS Conference on Neural Engineering, 2011

The introduction of micromachining technologies into design and development of interfaces to the ... more The introduction of micromachining technologies into design and development of interfaces to the peripheral nervous systems more than 20 years ago led to novel silicon and polymer based microimplants. Polyimide has been chosen as candidate for flexible implants. In this work, the investigations on different designs, the material stability and different aspects of biocompatibility as well as the functional outcome

ABSTRACT This paper reports development and characterisation of a novel hermetic packaging method... more ABSTRACT This paper reports development and characterisation of a novel hermetic packaging method for neuroprosthetic implants based on a ceramic hybrid onto which a metal cap is electroplated. In an automated accelerated lifetime test the packages are immersed in saline solution, while encapsulated humidity sensors measure intrusion of vapour. Assuming an Arrhenius relationship, a time of 66 days within the human body before onset of vapour intrusion can be predicted. The hermeticity of the packaging concept is further investigated by helium leak tests. The results demonstrate that the choice of glob-top material and process parameters is very critical.

In this work, we describe the fabrication of a polymer-based shaft electrode which can conduct li... more In this work, we describe the fabrication of a polymer-based shaft electrode which can conduct light as well as fluids to a target brain region and record electrical neural signals from the same tissue volume simultaneously. This multifunctional neural probe is intended to facilitate optogenetic in vivo experiments.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2006

Obtaining neural information from nerve cuff recordings for use as feedback signals for neural pr... more Obtaining neural information from nerve cuff recordings for use as feedback signals for neural prostheses is slowly becoming state-of-the-art. Traditional tripolar cuff recordings cannot provide information on the fiber type contributing to the compound electro neurogram. In order to get this data we employed a novel nerve cuff carrying eleven electrode contacts equally distributed along its axis. Connecting this cuff to a custom made low-noise ten-channel amplifier, a data acquisition system and applying some basic data processing routines, we were able to generate profiles that show, for the first time, the different propagation velocities that contribute to the whole nerve signal.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008

A laser technology for manufacturing implantable electrode arrays, using spin-on polydimethylsilo... more A laser technology for manufacturing implantable electrode arrays, using spin-on polydimethylsiloxane (PDMS) and platinum foil as materials, was investigated in respect to its scaling limitations. The following aspects were analyzed: Minimal width and centre-to-centre distance of platinum tracks, the ability of spin-on PDMS to flow between platinum tracks with very narrow gaps and the electrical insulation properties of thin spin-coated PDMS.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2009

An easy and fast method for fabrication of neural electrode arrays is the patterning of platinum ... more An easy and fast method for fabrication of neural electrode arrays is the patterning of platinum foil and spin-on silicone rubber using a laser. However, the mechanical flexibility of such electrode arrays is limited by the integrated tracks that connect the actual electrode sites and the contacts to which wires are welded. Changing the design from straight lines to meanders, the tracks can be stretched to a certain extend defined by the shape of the meanders. Horse-shoe-like designs described by an opening angle theta = 60 degrees and ratio between curvature radius r and track width w of r/w = 3.6 permitted stretching of 14.4% before track breakage. For r/w = 11.7 a maximum elongation at break of 19.7% was measured. Larger opening angles theta provided even better flexibility but with increasing theta, the tensile strength and the electrical conductance of a single track is compromised and the maximum integration density (tracks per area) decreases.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011

A blister test apparatus has been developed, which allows a quantitative adhesion analysis of thi... more A blister test apparatus has been developed, which allows a quantitative adhesion analysis of thin-film metallizations on polymers manufactured in cleanroom conditions suitable for micromachining of neural electrode arrays. The device is capable of pressurizing metallic membranes at wafer level, monitoring the pressure and the height of the developing blister while detecting the moment of delamination, allowing the calculation of the adhesion energy between metal film and polymer. The machine is designed for quantitative long-term studies of materials used in neural microelectrode arrays.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2012

Future brain-computer-interfaces (BCIs) for severely impaired patients are implanted to electrica... more Future brain-computer-interfaces (BCIs) for severely impaired patients are implanted to electrically contact the brain tissue. Avoiding percutaneous cables requires amplifier and telemetry electronics to be implanted too. We developed a hermetic package that protects the electronic circuitry of a BCI from body moisture while permitting infrared communication through the package wall made from alumina ceramic. The ceramic package is casted in medical grade silicone adhesive, for which we identified MED2-4013 as a promising candidate.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2014

In this paper, we introduce a technique for double-sealed ceramic packages for the long-term prot... more In this paper, we introduce a technique for double-sealed ceramic packages for the long-term protection of implanted electronics against body fluids. A sequential sealing procedure consisting of a first step, during which the package is sealed with epoxy, protecting the implant electronics from aggressive flux fumes. These result from the application of the actual moisture barrier which is a metal seal applied in a second step by soft soldering. Epoxy sealing is carried out in helium atmosphere for later fine leak testing. The solder seal is applied on the laboratory bench. After the first sealing step, a satisfactory barrier for moisture is already achieved with values for helium leakage of usually LHe = 6·10(-8) mbar 1 s(-1). After solder sealing, a very low leakage rate of LHe ≤ 1·10(-12) mbar 1 s(-1) was found, which was the lower detection limit of the measurement setup, suggesting excellent hermeticity and hence moisture barrier. Presuming an implant package volume of V ≥ 0.5 ...

2013 6th International IEEE/EMBS Conference on Neural Engineering (NER), 2013

ABSTRACT Strong permanent adhesion between thin-film polyimide (BPDA-PPD) and silicone rubber (ME... more ABSTRACT Strong permanent adhesion between thin-film polyimide (BPDA-PPD) and silicone rubber (MED-1000) was achieved through deposition of a chemically-transitive intermediate adhesion promoting layer. Plasma-enhanced chemical vapor deposition (PECVD) of SiC and SiO2 was used to grow a thin 50 nm layer directly on a 5 μm thin polyimide substrate. The deposition at low pressures permitted the fabrication of an adaptive covalent bond transition from sp2-hybridized carbon (in polyimide) towards the sp3 bonding in SiC, continuing to SiO2 which provides a good bonding partner for one-component poly-dimethyl siloxane (PDMS). The fabricated laminates together with reference probes containing no adhesion promoting layer were subjected to intense accelerated aging at 125°C and 130 kPa (pressure cooker) over 96 hrs in phosphate buffered saline solution. While the reference polyimide-PDMS laminates failed just after 30 min in the pressure cooker, no failure was detected on samples using the proposed adhesion promoter technique. Mechanical loading of the samples resulted in cohesive crack formation at the polyimide, propagating across the bulk with no evidence of adhesive failure between any of the materials. The strong permanent adhesion brings the fabrication of hybrid neural interfaces one step forward, achieving the combination of thin-film manufacturing and PDMS.

2013 6th International IEEE/EMBS Conference on Neural Engineering (NER), 2013

ABSTRACT We developed an implantable wireless, hermetically sealed brain-computer interface which... more ABSTRACT We developed an implantable wireless, hermetically sealed brain-computer interface which is intended to stay functional within the body for decades. Such an ambitious task demands interconnection technologies of high reliability and reproducibility. Investigating soft-soldering, poor wetting behavior of SnAg solder and destructive influences of additional fluxing materials excluded the lead-free compound from our list of suitable sealing and interconnection materials. We developed a robust and reliable welded interconnection method, which allows us to join a multichannel electrode array, even if materials such as MP35N are involved, which are inherently difficult to solder. For solder-sealing of the implant package with leakage rates in the desired range of

Peripheral nerve lesions lead to nerve degeneration and flaccid paralysis. The first objective in... more Peripheral nerve lesions lead to nerve degeneration and flaccid paralysis. The first objective in functional reha- bilitation of these diseases must be the preservation of the neuro-muscular junction by biological means. Sec- ondly, stimulation by means of neural prostheses may restore some function of the paralyzed limb. First suc- cess in implanting embryonic cells to preserve skeletal muscle has been reported. The combination of biologi- cal cells and technical microdevices to biohybrid sys- tems might become a new research field in neural pros- thetics. In this paper, a microdevice for a biohybrid sys- tem is presented that meets the most important technical requirements: adaptation to the distal nerve stump, suit- ability to combine the microstructure with a containment for cells, and integrated information transducers for cell stimulation and monitoring.

Sensors and Actuators A: Physical, 2002

A method for manufacturing¯exible neural implants with low-ohmic wire traces and improved stimula... more A method for manufacturing¯exible neural implants with low-ohmic wire traces and improved stimulation electrodes is presented together with the results of electrical characterization. The main objective is to reduce the resistance of the wire traces compared to currently used interconnects which are made from sputtered gold. This is achieved by electroplating to obtain a gold layer with a thickness of 2±3 mm. The resistance of the electroplated wire traces shows a reduction by a factor 30 and more compared to the sputtered wire traces. The electrode properties also improve (the electrode impedance is reduced to about a half due to the higher roughness of the gold surface) while the tests of the mechanical stability shows no increase in resistance when bending the implant up to 150,000 times in physiologic saline solution (0.9% NaCl) at 37 8C.

Sensors and Actuators A: Physical, 2005

Biomedical microimplants are used as neural prostheses to restore body functions after paraplegia... more Biomedical microimplants are used as neural prostheses to restore body functions after paraplegia by means of functional electrical stimulation (FES). This paper describes an approach of the integration of organic transistors into flexible biomedical microimplant for FES use. Encapsulation is used to ensure the electrical functionality of implants (insulation) and to protect them from the harsh environments in the human

Medical & Biological Engineering & Computing, 2011

Electrical impedance tomography (EIT) is a recently developed medical imaging method which has th... more Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. Previous modelling suggested that applied current needed to be below 100 Hz but the signal-to-noise ratio (SNR) recorded with scalp electrodes during evoked responses was too low to permit imaging. A novel method in which contemporaneous evoked potentials are subtracted is presented with current applied at 225 Hz to cerebral cortex during evoked activity; although the signal is smaller than at DC by about 109, the principal noise from the EEG is reduced by about 10009, resulting in an improved SNR. It was validated with recording of compound action potentials in crab walking leg nerve where peak changes of-0.2% at 125 and 175 Hz tallied with biophysical modelling. In recording from rat cerebral cortex during somatosensory evoked responses, peak impedance decreases of-0.07 ± 0.006% (mean ± SE) with a SNR of [50 could be recorded at 225 Hz. This method provides a reproducible and artefact free means for recording resistance changes during neuronal activity which could form the basis for imaging fast neural activity in the brain.

Medical & Biological Engineering & Computing, 2008

Using a multi-electrode nerve-signal recording cuff and a method of signal processing described p... more Using a multi-electrode nerve-signal recording cuff and a method of signal processing described previously, activity in axons with different propagation velocities can be distinguished, and the relative amplitude of the small-fibre signals increased. This paper is, largely, an analysis of the selectivity and noise of this system though impedance measurements from an actual cuff are included. The signal processor includes narrow band-pass filters. It is shown that the selectivity and noise both increase with the centre frequencies of these filters. A convenient approach is to make the filter frequencies inversely related to the artificial time delays so that the filter &amp;#39;Q&amp;#39;s are approximately constant and the noise densities are equal for all velocity filters. Numerical calculations, using formulae for this system and for the conventional tripole, based on a fixed cuff size and tissue resistivity, find the number of action potentials per second that must pass through the cuff so that the signal power equals the noise power. For slow fibres (20 m/s), the rate is 14 times lower for the multi-electrode cuff than the tripole, a significant advantage for recording from these fibres.