J. Hendricks - Academia.edu (original) (raw)
Papers by J. Hendricks
In Vitro and In Vivo Evaluation of PEDOT Microelectrodes for Neural Stimulation and Recording
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2011
Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural Prosthetic Devices
Frontiers in Neuroengineering Series, 2007
7 Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural ... more 7 Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural Prosthetic Devices Dong-Hwan Kim, Sarah Richardson-Burns, Laura Povlich, Mohammad Reza Abidian, Sarah Spanninga, Jeffrey L. Hendricks, and David C. Martin contents 7.1 Introduction................................................................................................. 177 7.2 Overview of Neural Prosthetic Devices............................................. ... ... 178 Indwelling Neural Implants devices have worked reasonably well in acute applications, chronically implanted electrodes have had ...
Poly(3,4-ethylenedioxythiophene) (PEDOT) polymer coatings facilitate smaller neural recording electrodes
Journal of Neural Engineering, 2011
Biomaterials, 2007
In this paper we describe interactions between neural cells and the conducting polymer poly(3,4et... more In this paper we describe interactions between neural cells and the conducting polymer poly(3,4ethylenedioxythiophene (PEDOT) toward development of electrically conductive biomaterials intended for direct, functional contact with electrically-active tissues such as the nervous system, heart, and skeletal muscle. We introduce a process for polymerizing PEDOT around living cells and describe a neural cell-templated conducting polymer coating for microelectrodes and a hybrid conducting polymer-live neural cell electrode. We found that neural cells could be exposed to working concentrations (0.01 M) of the EDOT monomer for as long as 72 hours while maintaining 80% cell viability. PEDOT could be electrochemically deposited around neurons cultured on electrodes using 0.5-1 μA/mm 2 galvanostatic current. PEDOT polymerized on the electrode and surrounded the cells, covering cell processes. The polymerization was impeded in regions where cells were well-adhered to the substrate. The cells could be removed from the PEDOT matrix to generate a neural cell-templated biomimetic conductive substrate with cell-shaped features that were cell-attracting. Live cells embedded within the conductive polymer matrix remained viable for at least 120 hours following polymerization. Dying cells primarily underwent apoptotic cell death. PEDOT, PEDOT+live neurons, and neuron-templated PEDOT coatings on electrodes significantly enhanced the electrical properties as compared to the bare electrode as indicated by decreased electrical impedance of 1-1.5 orders of magnitude at 0.01-1 kHz and significantly increased charge transfer capacity. PEDOT coatings showed a decrease of the phase angle of the impedance from roughly 80 degrees for the bare electrode to 5-35 degrees at frequencies >0.1 kHz. Equivalent circuit modeling indicated that PEDOT-coated electrodes were best described by R(C(RT)) circuit. We found that an RC parallel circuit must be added to the model for PEDOT+live neuron and neurontemplated PEDOT coatings.
Nanotechnology, 2011
A simple approach for creating periodic nano-cavities and periodic stripes of nano-cavity arrays ... more A simple approach for creating periodic nano-cavities and periodic stripes of nano-cavity arrays on poly (3,4-ethylene dioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) thin films using a combination of optical near-field enhancement through self-assembled silica nanospheres and laser interference lithography is presented. Monolayers of close-packed silica nanospheres (800, 600, and 430 nm in diameter) are self-assembled on 2 μm thick PEDOT-PSS electropolymerized films and are subsequently irradiated with 10 ns pulses of 355 nm wavelength laser light. Over areas spanning 2 cm 2 , circular nano-cavities with central holes of size 50-200 nm and surrounding craters of size 100-400 nm are formed in the PEDOT-PSS films directly underneath the nanospheres due to strong enhancement (11-18 fold) of the incident light in the near-field, which is confirmed through Mie scattering theory. Predictions from theoretical simulations examining the combined effects of near-field enhancement and interference are in good agreement with the experimental results. The results illustrate the versatility of the described technique for creating nano-cavity arrays or nano-pores in PEDOT-PSS over large areas with designed periodicity and hole size.
Journal of Neural Engineering, 2007
A number of biomedical devices require extended electrical communication with surrounding tissue.... more A number of biomedical devices require extended electrical communication with surrounding tissue. Significant improvements in device performance would be achieved if it were possible to maintain communication with target cells despite the reactive, insulating scar tissue that forms at the device-tissue interface. Here, we report that the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) can be polymerized directly within living neural tissue resulting in an electrically conductive network that is integrated within the tissue. Nano and microscale PEDOT filaments extend out from electrode sites, presumably forming within extracellular spaces. The cloud of PEDOT filaments penetrates out into the tissue far enough that it should be possible to bypass fibrous scar tissue and contact surrounding healthy neurons. These electrically functional, diffuse conducting polymer networks grown directly within tissue signify a new paradigm for creating soft, low impedance implantable electrodes.
Microscopy and Microanalysis, 2006
We are actively investigating the use of conducting polymers such as poly(3,4ethylenedioxythiophe... more We are actively investigating the use of conducting polymers such as poly(3,4ethylenedioxythiophene) (PEDOT) for functionalizing the surfaces of biomedical devices designed to interface with living tissue. These include microfabricated electrodes intended for insertion into the cortex, as well as deep brain stimulators, retinal implants, and cochlear implants. These materials must accommodate the dramatic differences in mechanical properties, biological activity, and mechanisms of charge transport across the abiotic-biotic interface from engineered device to living cells.
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2011
Cortical neural prostheses require chronically implanted small-area microelectrode arrays that si... more Cortical neural prostheses require chronically implanted small-area microelectrode arrays that simultaneously record and stimulate neural activity. It is necessary to develop new materials with low interface impedance and large charge transfer capacity for this application and we explore the use of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) for the same. We subjected PEDOT coated electrodes to voltage cycling between 0.6 and 0.8 V, 24 h continuous biphasic stimulation at 3 mC cm 2 and accelerated aging for four weeks. Characterization was performed using cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient measurements. We found that PEDOT coated electrodes showed a charge injection limit 15 times higher than Platinum Iridium (PtIr) electrodes and electroplated Iridium Oxide (IrOx) electrodes when using constant current stimulation at zero voltage bias. In vivo chronic testing of microelectrode arrays implanted in rat cortex revealed that PEDOT coated electrodes show higher signal-to-noise recordings and superior charge injection compared to PtIr electrodes.
In Vitro and In Vivo Evaluation of PEDOT Microelectrodes for Neural Stimulation and Recording
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2011
Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural Prosthetic Devices
Frontiers in Neuroengineering Series, 2007
7 Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural ... more 7 Soft, Fuzzy, and Bioactive Conducting Polymers for Improving the Chronic Performance of Neural Prosthetic Devices Dong-Hwan Kim, Sarah Richardson-Burns, Laura Povlich, Mohammad Reza Abidian, Sarah Spanninga, Jeffrey L. Hendricks, and David C. Martin contents 7.1 Introduction................................................................................................. 177 7.2 Overview of Neural Prosthetic Devices............................................. ... ... 178 Indwelling Neural Implants devices have worked reasonably well in acute applications, chronically implanted electrodes have had ...
Poly(3,4-ethylenedioxythiophene) (PEDOT) polymer coatings facilitate smaller neural recording electrodes
Journal of Neural Engineering, 2011
Biomaterials, 2007
In this paper we describe interactions between neural cells and the conducting polymer poly(3,4et... more In this paper we describe interactions between neural cells and the conducting polymer poly(3,4ethylenedioxythiophene (PEDOT) toward development of electrically conductive biomaterials intended for direct, functional contact with electrically-active tissues such as the nervous system, heart, and skeletal muscle. We introduce a process for polymerizing PEDOT around living cells and describe a neural cell-templated conducting polymer coating for microelectrodes and a hybrid conducting polymer-live neural cell electrode. We found that neural cells could be exposed to working concentrations (0.01 M) of the EDOT monomer for as long as 72 hours while maintaining 80% cell viability. PEDOT could be electrochemically deposited around neurons cultured on electrodes using 0.5-1 μA/mm 2 galvanostatic current. PEDOT polymerized on the electrode and surrounded the cells, covering cell processes. The polymerization was impeded in regions where cells were well-adhered to the substrate. The cells could be removed from the PEDOT matrix to generate a neural cell-templated biomimetic conductive substrate with cell-shaped features that were cell-attracting. Live cells embedded within the conductive polymer matrix remained viable for at least 120 hours following polymerization. Dying cells primarily underwent apoptotic cell death. PEDOT, PEDOT+live neurons, and neuron-templated PEDOT coatings on electrodes significantly enhanced the electrical properties as compared to the bare electrode as indicated by decreased electrical impedance of 1-1.5 orders of magnitude at 0.01-1 kHz and significantly increased charge transfer capacity. PEDOT coatings showed a decrease of the phase angle of the impedance from roughly 80 degrees for the bare electrode to 5-35 degrees at frequencies >0.1 kHz. Equivalent circuit modeling indicated that PEDOT-coated electrodes were best described by R(C(RT)) circuit. We found that an RC parallel circuit must be added to the model for PEDOT+live neuron and neurontemplated PEDOT coatings.
Nanotechnology, 2011
A simple approach for creating periodic nano-cavities and periodic stripes of nano-cavity arrays ... more A simple approach for creating periodic nano-cavities and periodic stripes of nano-cavity arrays on poly (3,4-ethylene dioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) thin films using a combination of optical near-field enhancement through self-assembled silica nanospheres and laser interference lithography is presented. Monolayers of close-packed silica nanospheres (800, 600, and 430 nm in diameter) are self-assembled on 2 μm thick PEDOT-PSS electropolymerized films and are subsequently irradiated with 10 ns pulses of 355 nm wavelength laser light. Over areas spanning 2 cm 2 , circular nano-cavities with central holes of size 50-200 nm and surrounding craters of size 100-400 nm are formed in the PEDOT-PSS films directly underneath the nanospheres due to strong enhancement (11-18 fold) of the incident light in the near-field, which is confirmed through Mie scattering theory. Predictions from theoretical simulations examining the combined effects of near-field enhancement and interference are in good agreement with the experimental results. The results illustrate the versatility of the described technique for creating nano-cavity arrays or nano-pores in PEDOT-PSS over large areas with designed periodicity and hole size.
Journal of Neural Engineering, 2007
A number of biomedical devices require extended electrical communication with surrounding tissue.... more A number of biomedical devices require extended electrical communication with surrounding tissue. Significant improvements in device performance would be achieved if it were possible to maintain communication with target cells despite the reactive, insulating scar tissue that forms at the device-tissue interface. Here, we report that the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) can be polymerized directly within living neural tissue resulting in an electrically conductive network that is integrated within the tissue. Nano and microscale PEDOT filaments extend out from electrode sites, presumably forming within extracellular spaces. The cloud of PEDOT filaments penetrates out into the tissue far enough that it should be possible to bypass fibrous scar tissue and contact surrounding healthy neurons. These electrically functional, diffuse conducting polymer networks grown directly within tissue signify a new paradigm for creating soft, low impedance implantable electrodes.
Microscopy and Microanalysis, 2006
We are actively investigating the use of conducting polymers such as poly(3,4ethylenedioxythiophe... more We are actively investigating the use of conducting polymers such as poly(3,4ethylenedioxythiophene) (PEDOT) for functionalizing the surfaces of biomedical devices designed to interface with living tissue. These include microfabricated electrodes intended for insertion into the cortex, as well as deep brain stimulators, retinal implants, and cochlear implants. These materials must accommodate the dramatic differences in mechanical properties, biological activity, and mechanisms of charge transport across the abiotic-biotic interface from engineered device to living cells.
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2011
Cortical neural prostheses require chronically implanted small-area microelectrode arrays that si... more Cortical neural prostheses require chronically implanted small-area microelectrode arrays that simultaneously record and stimulate neural activity. It is necessary to develop new materials with low interface impedance and large charge transfer capacity for this application and we explore the use of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) for the same. We subjected PEDOT coated electrodes to voltage cycling between 0.6 and 0.8 V, 24 h continuous biphasic stimulation at 3 mC cm 2 and accelerated aging for four weeks. Characterization was performed using cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient measurements. We found that PEDOT coated electrodes showed a charge injection limit 15 times higher than Platinum Iridium (PtIr) electrodes and electroplated Iridium Oxide (IrOx) electrodes when using constant current stimulation at zero voltage bias. In vivo chronic testing of microelectrode arrays implanted in rat cortex revealed that PEDOT coated electrodes show higher signal-to-noise recordings and superior charge injection compared to PtIr electrodes.