2006 IEEE Workshop on Microelectronics and Electron Devices, 2006. WMED '06., 2006
For the conventional Utah electrode array (UEA) to be able to function without transcutaneous wir... more For the conventional Utah electrode array (UEA) to be able to function without transcutaneous wire connections, a kind of power source is needed in an integrated form with the UEA. To develop such wireless neural interfaces, inductive coupling between two coils was used to deliver power to the integrated electronics. The power receiver coil was microfabricated as a polymer based component, and its electrical characteristics and performance in power transmission were investigated in dry condition
20th International Conference on VLSI Design held jointly with 6th International Conference on Embedded Systems (VLSID'07), 2007
We have developed a single-chip neural recording system with wireless power delivery and telemetr... more We have developed a single-chip neural recording system with wireless power delivery and telemetry. The 0.5-µm CMOS IC is designed to be bonded to the back of a 100-channel Utah Electrode Array. A pad near each amplifier allows connection of the chip to the MEMS ...
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010
Neural electrodes represent the direct interface between the biological and the electronic system... more Neural electrodes represent the direct interface between the biological and the electronic system. Electrodes are used for both recording of neural signals and stimulation of nerves and muscles. It is critical that the electrode material is biocompatible and electrically and mechanically stable so that the electrode neither dissolve/degrade while stimulation of neural tissue, nor change its properties. In this study,
2010 Proceedings 60th Electronic Components and Technology Conference (ECTC), 2010
Microfabricated microelectrode arrays are used to record and stimulate neurons and nerve axons in... more Microfabricated microelectrode arrays are used to record and stimulate neurons and nerve axons in the central and peripheral nervous systems. Advances in silicon micromachining have brought forth new configurations of microelectrode structures, such as the Utah Electrode Array (UEA). This paper presents a novel monolithic integration technology to realize a flexible neural interface in which a biocompatible polymer (Parylene-C) mechanically
Reliable chronic operation of implantable medical devices such as the Utah Electrode Array (UEA) ... more Reliable chronic operation of implantable medical devices such as the Utah Electrode Array (UEA) for neural interface requires elimination of transcutaneous wire connections for signal processing, powering and communication of the device. A wireless power source that allows integration with the UEA is therefore necessary. While (rechargeable) micro batteries as well as biological micro fuel cells are yet far from meeting the power density and lifetime requirements of an implantable neural interface device, inductive coupling between two coils is a promising approach to power such a device with highly restricted dimensions. The power receiving coils presented in this paper were designed to maximize the inductance and quality factor of the coils and microfabricated using polymer based thin film technologies. A flexible configuration of stacked thin film coils allows parallel and serial switching, thereby allowing to tune the coil's resonance frequency. The electrical properties of...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Stimuli responsive hydrogels show a strong ability to change in volume with changes in selected e... more Stimuli responsive hydrogels show a strong ability to change in volume with changes in selected environmental properties. This tendency of these hydrogels to change in volume is captured as pressure-change in confined cavities of pressure sensors. An array of pressure sensors on a single chip may carry hydrogels sensitive to multiple, selected metabolic markers and continuously monitor multiple vital parameters simultaneously. Currently, such sensors are capable of continuously monitoring pH, ionic strength, glucose levels and temperature in the sensor environment. In this paper, we report the effect of temperature changes on the performance of ionic strength sensor. A formulation of hydrogel that renders it sensitive to changes in ionic strength was UV polymerized in situ in piezoresistive pressure sensors with different membrane sizes. The sensor sensitivity, response time and stability are investigated as a function of temperature in vitro. The effect of temperature on these sens...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2010
In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels... more In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels, confined in micro-pressure sensors, to the changes in environmental glucose concentration. The glucose concentrations were incrementally varied between 20 and 0mM in 0.15M PBS solution at 7.4 pH and bovine serum at 7.4 pH at room temperature and response of the sensor was recorded. The micro sensors demonstrate a response time of 10 minutes in both PBS and serum. Tissue response after 55 days of subcutaneous implantation of a EtO sterilized sensor in mice is presented. The preliminary analysis of the surrounding tissue shows inflammation which is believed not to interfere with the sensor performance.
Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah ... more Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah electrode array (UEA), intended for recording and stimulating neural tissue. Fabrication of the UEA is primarily based on the use of dicing and wet etching to achieve high aspect ratio (15:1) penetrating electrodes. An important step in the array fabrication is the etching of electrodes to produce needle-shape electrodes with sharp tips. Traditional etching processes are performed on a single array, and the etching conditions are not optimized. As a result, the process leads to variable geometries of electrodes within an array. Furthermore, the process is not only time consuming but also labor-intensive. This report presents a wafer-scale etching method for the UEA. The method offers several advantages, such as substantial reduction in the processing time, higher throughput and lower cost. More importantly, the method increases the geometrical uniformity from electrode to electrode withi...
Electroactive Polymer Actuators and Devices (EAPAD) 2011, 2011
With the rapid development of micro systems technology and microelectronics, smart electronic sys... more With the rapid development of micro systems technology and microelectronics, smart electronic systems are emerging for the continuous surveillance of relevant parameters in the body and even for closed-loop systems with a sensor feedback to drug release systems. With respect to diabetes management, there is a critical societal need for a sensor that can be used to continuously measure a patient's blood glucose concentration twenty four hours a day on a long-term basis. In this work, thin films of "stimuli-responsive" or "smart" hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain "chemomechanical sensors" that can serve as selective and versatile wireless biomedical sensors. The sensitivity of hydrogels with regard to the concentration of glucose in solutions with physiological pH, ionic strength and temperature was investigated in vitro. The response of the glucose-sensitive hydrogel was studied at different regimes of the glucose concentration change and at different temperatures. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated.
Electroactive Polymer Actuators and Devices (EAPAD) 2010, 2010
ABSTRACT This work is motivated by a demand for inexpensive, robust and reliable biochemical sens... more ABSTRACT This work is motivated by a demand for inexpensive, robust and reliable biochemical sensors with high signal reproducibility and long-term-stable sensitivity, especially for medical applications. Micro-fabricated sensors can provide continuous monitoring and on-line control of analyte concentrations in ambient aqueous solutions. The piezoresistive biochemical sensor containing a special biocompatible polymer (hydrogel) with a sharp volume phase transition in the neutral physiological pH range near 7.4 can detect a specific analyte, for example glucose. Thereby the hydrogel-based biochemical sensors are useful for the diagnosis and monitoring of diabetes. The response of the glucose-sensitive hydrogel was studied at different regimes of the glucose concentration change and of the solution supply. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated. Additionally, the influence of various recommended sterilization methods on the gel swelling properties and on the mechano-electrical transducer of the pH-sensors has been evaluated in order to choose the most optimal sterilization method for the implantable sensors. It has been shown that there is no negative effect of gamma irradiation with a dose of 25.7 kGy on the hydrogel sensitivity. In order to achieve an optimum between sensor signal amplitude and sensor response time, corresponding calibration and measurement procedures have been proposed and evaluated for the chemical sensors.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2006
One requirement of a chronically implantable, wireless neural interface device is the integration... more One requirement of a chronically implantable, wireless neural interface device is the integration of electronic circuitry with the microelectrode array. Since the electronic IC dissipates a certain amount of power, it will affect the temperature in the tissues surrounding the implant site. In this paper, the thermal influence of an integrated, 3-dimensional Utah electrode array, to be implanted in the brain was investigated with simulations using the finite element method (FEM). A temperature increase in the brain tissue was predicted using preliminary simulations with simplified models. The model and method used in the simulations were verified by simple in vitro experiments.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
In an integrated wireless neural interface based on the Utah electrode array, the implanted elect... more In an integrated wireless neural interface based on the Utah electrode array, the implanted electronics is supplied with power through inductive coupling between two coils. This inductive power link would be affected by conductive and dielectric media surrounding the implant coil. In this study, the influences of the integration of implant coil on silicon based IC/electrode, thin film parylene coating, and physiological medium surrounding the coil were investigated systematically and quantitatively. A few different versions of implant coils were made by winding fine wire with a diameter of around 50 microm. The parasitic influences affecting the inductive power link were empirically investigated by measuring the electrical properties of coils in different configurations and in different media. The distance of power transmission between the transmit and receive coils was measured when the receive coil was in air and immersed in saline solution to simulate an implanted physiological e...
Electronic Components and Technology Conference, 2008
This paper presents a novel design and development of a self-aligning latch-up mechanism for out ... more This paper presents a novel design and development of a self-aligning latch-up mechanism for out of plane, high density, three dimensional penetrating micro electrode array used for neural prosthesis. The microsystem consists of two components; male and female. The male component has 100 neural electrodes with one row of edge column having a "mushroom" geometry, and corner posts at the
Active and Passive Smart Structures and Integrated Systems 2007, 2007
The advent of micro and nanotechnologies along with integrated circuit technologies has led to ma... more The advent of micro and nanotechnologies along with integrated circuit technologies has led to many exciting solutions in medical field. One of the major applications of microsystems is microelectrodes interfacing neurons for large scale in vivo sensing, deep brain stimulation and recording. For biomedical microsystems, material selection is a challenge because biocompatibility has to be considered for implantable electronic devices.
2006 IEEE Workshop on Microelectronics and Electron Devices, 2006. WMED '06., 2006
For the conventional Utah electrode array (UEA) to be able to function without transcutaneous wir... more For the conventional Utah electrode array (UEA) to be able to function without transcutaneous wire connections, a kind of power source is needed in an integrated form with the UEA. To develop such wireless neural interfaces, inductive coupling between two coils was used to deliver power to the integrated electronics. The power receiver coil was microfabricated as a polymer based component, and its electrical characteristics and performance in power transmission were investigated in dry condition
20th International Conference on VLSI Design held jointly with 6th International Conference on Embedded Systems (VLSID'07), 2007
We have developed a single-chip neural recording system with wireless power delivery and telemetr... more We have developed a single-chip neural recording system with wireless power delivery and telemetry. The 0.5-µm CMOS IC is designed to be bonded to the back of a 100-channel Utah Electrode Array. A pad near each amplifier allows connection of the chip to the MEMS ...
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010
Neural electrodes represent the direct interface between the biological and the electronic system... more Neural electrodes represent the direct interface between the biological and the electronic system. Electrodes are used for both recording of neural signals and stimulation of nerves and muscles. It is critical that the electrode material is biocompatible and electrically and mechanically stable so that the electrode neither dissolve/degrade while stimulation of neural tissue, nor change its properties. In this study,
2010 Proceedings 60th Electronic Components and Technology Conference (ECTC), 2010
Microfabricated microelectrode arrays are used to record and stimulate neurons and nerve axons in... more Microfabricated microelectrode arrays are used to record and stimulate neurons and nerve axons in the central and peripheral nervous systems. Advances in silicon micromachining have brought forth new configurations of microelectrode structures, such as the Utah Electrode Array (UEA). This paper presents a novel monolithic integration technology to realize a flexible neural interface in which a biocompatible polymer (Parylene-C) mechanically
Reliable chronic operation of implantable medical devices such as the Utah Electrode Array (UEA) ... more Reliable chronic operation of implantable medical devices such as the Utah Electrode Array (UEA) for neural interface requires elimination of transcutaneous wire connections for signal processing, powering and communication of the device. A wireless power source that allows integration with the UEA is therefore necessary. While (rechargeable) micro batteries as well as biological micro fuel cells are yet far from meeting the power density and lifetime requirements of an implantable neural interface device, inductive coupling between two coils is a promising approach to power such a device with highly restricted dimensions. The power receiving coils presented in this paper were designed to maximize the inductance and quality factor of the coils and microfabricated using polymer based thin film technologies. A flexible configuration of stacked thin film coils allows parallel and serial switching, thereby allowing to tune the coil's resonance frequency. The electrical properties of...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Stimuli responsive hydrogels show a strong ability to change in volume with changes in selected e... more Stimuli responsive hydrogels show a strong ability to change in volume with changes in selected environmental properties. This tendency of these hydrogels to change in volume is captured as pressure-change in confined cavities of pressure sensors. An array of pressure sensors on a single chip may carry hydrogels sensitive to multiple, selected metabolic markers and continuously monitor multiple vital parameters simultaneously. Currently, such sensors are capable of continuously monitoring pH, ionic strength, glucose levels and temperature in the sensor environment. In this paper, we report the effect of temperature changes on the performance of ionic strength sensor. A formulation of hydrogel that renders it sensitive to changes in ionic strength was UV polymerized in situ in piezoresistive pressure sensors with different membrane sizes. The sensor sensitivity, response time and stability are investigated as a function of temperature in vitro. The effect of temperature on these sens...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2010
In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels... more In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels, confined in micro-pressure sensors, to the changes in environmental glucose concentration. The glucose concentrations were incrementally varied between 20 and 0mM in 0.15M PBS solution at 7.4 pH and bovine serum at 7.4 pH at room temperature and response of the sensor was recorded. The micro sensors demonstrate a response time of 10 minutes in both PBS and serum. Tissue response after 55 days of subcutaneous implantation of a EtO sterilized sensor in mice is presented. The preliminary analysis of the surrounding tissue shows inflammation which is believed not to interfere with the sensor performance.
Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah ... more Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah electrode array (UEA), intended for recording and stimulating neural tissue. Fabrication of the UEA is primarily based on the use of dicing and wet etching to achieve high aspect ratio (15:1) penetrating electrodes. An important step in the array fabrication is the etching of electrodes to produce needle-shape electrodes with sharp tips. Traditional etching processes are performed on a single array, and the etching conditions are not optimized. As a result, the process leads to variable geometries of electrodes within an array. Furthermore, the process is not only time consuming but also labor-intensive. This report presents a wafer-scale etching method for the UEA. The method offers several advantages, such as substantial reduction in the processing time, higher throughput and lower cost. More importantly, the method increases the geometrical uniformity from electrode to electrode withi...
Electroactive Polymer Actuators and Devices (EAPAD) 2011, 2011
With the rapid development of micro systems technology and microelectronics, smart electronic sys... more With the rapid development of micro systems technology and microelectronics, smart electronic systems are emerging for the continuous surveillance of relevant parameters in the body and even for closed-loop systems with a sensor feedback to drug release systems. With respect to diabetes management, there is a critical societal need for a sensor that can be used to continuously measure a patient's blood glucose concentration twenty four hours a day on a long-term basis. In this work, thin films of "stimuli-responsive" or "smart" hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain "chemomechanical sensors" that can serve as selective and versatile wireless biomedical sensors. The sensitivity of hydrogels with regard to the concentration of glucose in solutions with physiological pH, ionic strength and temperature was investigated in vitro. The response of the glucose-sensitive hydrogel was studied at different regimes of the glucose concentration change and at different temperatures. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated.
Electroactive Polymer Actuators and Devices (EAPAD) 2010, 2010
ABSTRACT This work is motivated by a demand for inexpensive, robust and reliable biochemical sens... more ABSTRACT This work is motivated by a demand for inexpensive, robust and reliable biochemical sensors with high signal reproducibility and long-term-stable sensitivity, especially for medical applications. Micro-fabricated sensors can provide continuous monitoring and on-line control of analyte concentrations in ambient aqueous solutions. The piezoresistive biochemical sensor containing a special biocompatible polymer (hydrogel) with a sharp volume phase transition in the neutral physiological pH range near 7.4 can detect a specific analyte, for example glucose. Thereby the hydrogel-based biochemical sensors are useful for the diagnosis and monitoring of diabetes. The response of the glucose-sensitive hydrogel was studied at different regimes of the glucose concentration change and of the solution supply. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated. Additionally, the influence of various recommended sterilization methods on the gel swelling properties and on the mechano-electrical transducer of the pH-sensors has been evaluated in order to choose the most optimal sterilization method for the implantable sensors. It has been shown that there is no negative effect of gamma irradiation with a dose of 25.7 kGy on the hydrogel sensitivity. In order to achieve an optimum between sensor signal amplitude and sensor response time, corresponding calibration and measurement procedures have been proposed and evaluated for the chemical sensors.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2006
One requirement of a chronically implantable, wireless neural interface device is the integration... more One requirement of a chronically implantable, wireless neural interface device is the integration of electronic circuitry with the microelectrode array. Since the electronic IC dissipates a certain amount of power, it will affect the temperature in the tissues surrounding the implant site. In this paper, the thermal influence of an integrated, 3-dimensional Utah electrode array, to be implanted in the brain was investigated with simulations using the finite element method (FEM). A temperature increase in the brain tissue was predicted using preliminary simulations with simplified models. The model and method used in the simulations were verified by simple in vitro experiments.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
In an integrated wireless neural interface based on the Utah electrode array, the implanted elect... more In an integrated wireless neural interface based on the Utah electrode array, the implanted electronics is supplied with power through inductive coupling between two coils. This inductive power link would be affected by conductive and dielectric media surrounding the implant coil. In this study, the influences of the integration of implant coil on silicon based IC/electrode, thin film parylene coating, and physiological medium surrounding the coil were investigated systematically and quantitatively. A few different versions of implant coils were made by winding fine wire with a diameter of around 50 microm. The parasitic influences affecting the inductive power link were empirically investigated by measuring the electrical properties of coils in different configurations and in different media. The distance of power transmission between the transmit and receive coils was measured when the receive coil was in air and immersed in saline solution to simulate an implanted physiological e...
Electronic Components and Technology Conference, 2008
This paper presents a novel design and development of a self-aligning latch-up mechanism for out ... more This paper presents a novel design and development of a self-aligning latch-up mechanism for out of plane, high density, three dimensional penetrating micro electrode array used for neural prosthesis. The microsystem consists of two components; male and female. The male component has 100 neural electrodes with one row of edge column having a "mushroom" geometry, and corner posts at the
Active and Passive Smart Structures and Integrated Systems 2007, 2007
The advent of micro and nanotechnologies along with integrated circuit technologies has led to ma... more The advent of micro and nanotechnologies along with integrated circuit technologies has led to many exciting solutions in medical field. One of the major applications of microsystems is microelectrodes interfacing neurons for large scale in vivo sensing, deep brain stimulation and recording. For biomedical microsystems, material selection is a challenge because biocompatibility has to be considered for implantable electronic devices.
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