Micromachined three-dimensional electrode arrays for transcutaneous nerve tracking

We report the development of metal transfer micromolded (MTM) three-dimensional microelectrode arrays (3D MEAs) for a transcutaneous nerve tracking application. The measurements of electrode?skin?electrode impedance (ESEI), electromyography (EMG) and nerve conduction utilizing these minimally invasive 3D MEAs are demonstrated in this paper. The 3D MEAs used in these measurements consist of a metalized micro-tower array that can penetrate the outer layers of the skin in a painless fashion and are fabricated using MTM technology. Two techniques, an inclined UV lithography approach and a double-side exposure of thick negative tone resist, have been developed to fabricate the 3D MEA master structure. The MEAs themselves are fabricated from the master structure utilizing micromolding techniques. Metal patterns are transferred during the micromolding process, thereby ensuring reduced process steps compared to traditional silicon-based approaches. These 3D MEAs have been packaged utilizing biocompatible Kapton? substrates. ESEI measurements have been carried out on test human subjects with standard commercial wet electrodes as a reference. The 3D MEAs demonstrate an order of magnitude lower ESEI (normalized to area) compared to wet electrodes for an area that is 12.56 times smaller. This compares well with other demonstrated approaches in literature. For a nerve tracking demonstration, we have chosen EMG and nerve conduction measurements on test human subjects. The 3D MEAs show 100% improvement in signal power and SNR/?area as compared to standard electrodes. They also demonstrate larger amplitude signals and faster rise times during nerve conduction measurements. We believe that this microfabrication and packaging approach scales well to large-area, high-density arrays required for applications like nerve tracking. This development will increase the stimulation and recording fidelity of skin surface electrodes, while increasing their spatial resolution by an order of magnitude or more. Although biopotential electrode systems are not without their challenges, the non-invasive access to neural information, along with the potential for automation with associated electronic and software development, is precisely what makes this technology an excellent candidate for the next generation in diagnostic, therapeutic, and prosthetic devices.

[1]  C. Dwyer,et al.  Allergic contact dermatitis from TENS gel , 1994, Contact dermatitis.

[2]  Cheng-Ning Huang,et al.  The Review of Applications and Measurements in Facial Electromyography , 2004 .

[3]  P. Vettiger,et al.  Fabrication of photoplastic high-aspect ratio microparts and micromolds using SU-8 UV resist , 1998 .

[4]  M. Allen,et al.  Three dimensional metal pattern transfer for replica molded microstructures , 2009 .

[5]  Yong-Kyu Yoon,et al.  Multidirectional UV Lithography for Complex 3-D MEMS Structures , 2006, Journal of Microelectromechanical Systems.

[6]  J. Garra,et al.  Dry etching of polydimethylsiloxane for microfluidic systems , 2002 .

[7]  Jung-Hwan Park,et al.  Tapered Conical Polymer Microneedles Fabricated Using an Integrated Lens Technique for Transdermal Drug Delivery , 2007, IEEE Transactions on Biomedical Engineering.

[8]  Harry A. Miller,et al.  Biomedical electrode technology: theory and practice , 1974 .

[9]  Tzyy-Ping Jung,et al.  Noninvasive Neural Prostheses Using Mobile and Wireless EEG , 2008, Proceedings of the IEEE.

[10]  C. Grimbergen,et al.  Investigation into the origin of the noise of surface electrodes , 2002, Medical and Biological Engineering and Computing.

[11]  R. Knight,et al.  An Active, Microfabricated, Scalp Electrode-array For EEG Recording , 1995, Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95.

[12]  James C. White,et al.  A comparison of EMG procedures in the carpal tunnel syndrome with clinical‐EMG correlations , 1988, Muscle & nerve.

[13]  Roland Zengerle,et al.  Multi-layer SU-8 lift-off technology for microfluidic devices , 2005 .

[14]  Terry J. Housh,et al.  Mechanomyographic and electromyographic responses of the superficial muscles of the quadriceps femoris during maximal, concentric isokinetic muscle actions , 2000 .

[15]  S. Nishimura,et al.  Clinical application of an active electrode using an operational amplifier , 1992, IEEE Transactions on Biomedical Engineering.

[16]  Göran Stemme,et al.  Characterization of micromachined spiked biopotential electrodes , 2002, IEEE Transactions on Biomedical Engineering.

[17]  David Juncker,et al.  Soft and rigid two-level microfluidic networks for patterning surfaces , 2001 .

[18]  E. Scherder,et al.  Effects of short-term transcutaneous electrical nerve stimulation on memory and affective behaviour in patients with probable Alzheimer's disease , 1995, Behavioural Brain Research.

[19]  W Uter,et al.  Contact dermatitis from propylene glycol in ECG electrode gel , 1996, Contact dermatitis.

[20]  Polymer inking as a micro- and nanopatterning technique , 2003 .

[21]  F. Granella,et al.  Headache and Cervical Spine Disorders: Classification and Treatment with Transcutaneous Electrical Nerve Stimulation , 1986, Headache.

[22]  K.D. Wise,et al.  Silicon microsystems for neuroscience and neural prostheses , 2005, IEEE Engineering in Medicine and Biology Magazine.

[23]  Robert T. Knight,et al.  An active, microfabricated, scalp electrode array for EEG recording , 1996 .

[24]  C. Disselhorst-Klug,et al.  Non-invasive approach of motor unit recording during muscle contractions in humans , 2000, European Journal of Applied Physiology.

[25]  Seong-O Choi,et al.  An Electrically Active Microneedle Electroporation Array for Intracellular Delivery of Biomolecules , 2007 .

[26]  John A. Rogers,et al.  Nanotransfer printing by use of noncovalent surface forces: Applications to thin-film transistors that use single-walled carbon nanotube networks and semiconducting polymers , 2004 .

[27]  L. Kirkup,et al.  A direct comparison of wet, dry and insulating bioelectric recording electrodes. , 2000, Physiological measurement.

[28]  Peter Vettiger,et al.  High-aspect-ratio, ultrathick, negative-tone near-UV photoresist and its applications for MEMS , 1998 .

[29]  Tzyy-Ping Jung,et al.  A brain-machine interface using dry-contact, low-noise EEG sensors , 2008, 2008 IEEE International Symposium on Circuits and Systems.

[30]  Peter Enoksson,et al.  Micromachined electrodes for biopotential measurements , 2001 .