Response of brain tissue to chronically implanted neural electrodes.

http://drugdelivery.chbe.gatech.edu/Papers/2004/Prausnitz%20ADDR%202004.pdf

Microneedles for transdermal drug delivery.

Part I: Background and Fundamentals Introduction, Mohamed Gad-el-Hak, University of Notre Dame Scaling of Micromechanical Devices, William Trimmer, Standard MEMS, Inc., and Robert H. Stroud, Aerospace Corporation Mechanical Properties of MEMS Materials, William N. Sharpe, Jr., Johns Hopkins University Flow Physics, Mohamed Gad-el-Hak, University of Notre Dame Integrated Simulation for MEMS: Coupling Flow-Structure-Thermal-Electrical Domains, Robert M. Kirby and George Em Karniadakis, Brown University, and Oleg Mikulchenko and Kartikeya Mayaram, Oregon State University Liquid Flows in Microchannels, Kendra V. Sharp and Ronald J. Adrian, University of Illinois at Urbana-Champaign, Juan G. Santiago and Joshua I. Molho, Stanford University Burnett Simulations of Flows in Microdevices, Ramesh K. Agarwal and Keon-Young Yun, Wichita State University Molecular-Based Microfluidic Simulation Models, Ali Beskok, Texas A&M University Lubrication in MEMS, Kenneth S. Breuer, Brown University Physics of Thin Liquid Films, Alexander Oron, Technion, Israel Bubble/Drop Transport in Microchannels, Hsueh-Chia Chang, University of Notre Dame Fundamentals of Control Theory, Bill Goodwine, University of Notre Dame Model-Based Flow Control for Distributed Architectures, Thomas R. Bewley, University of California, San Diego Soft Computing in Control, Mihir Sen and Bill Goodwine, University of Notre Dame Part II: Design and Fabrication Materials for Microelectromechanical Systems Christian A. Zorman and Mehran Mehregany, Case Western Reserve University MEMS Fabrication, Marc J. Madou, Nanogen, Inc. LIGA and Other Replication Techniques, Marc J. Madou, Nanogen, Inc. X-Ray-Based Fabrication, Todd Christenson, Sandia National Laboratories Electrochemical Fabrication (EFAB), Adam L. Cohen, MEMGen Corporation Fabrication and Characterization of Single-Crystal Silicon Carbide MEMS, Robert S. Okojie, NASA Glenn Research Center Deep Reactive Ion Etching for Bulk Micromachining of Silicon Carbide, Glenn M. Beheim, NASA Glenn Research Center Microfabricated Chemical Sensors for Aerospace Applications, Gary W. Hunter, NASA Glenn Research Center, Chung-Chiun Liu, Case Western Reserve University, and Darby B. Makel, Makel Engineering, Inc. Packaging of Harsh-Environment MEMS Devices, Liang-Yu Chen and Jih-Fen Lei, NASA Glenn Research Center Part III: Applications of MEMS Inertial Sensors, Paul L. Bergstrom, Michigan Technological University, and Gary G. Li, OMM, Inc. Micromachined Pressure Sensors, Jae-Sung Park, Chester Wilson, and Yogesh B. Gianchandani, University of Wisconsin-Madison Sensors and Actuators for Turbulent Flows. Lennart Loefdahl, Chalmers University of Technology, and Mohamed Gad-el-Hak, University of Notre Dame Surface-Micromachined Mechanisms, Andrew D. Oliver and David W. Plummer, Sandia National Laboratories Microrobotics Thorbjoern Ebefors and Goeran Stemme, Royal Institute of Technology, Sweden Microscale Vacuum Pumps, E. Phillip Muntz, University of Southern California, and Stephen E. Vargo, SiWave, Inc. Microdroplet Generators. Fan-Gang Tseng, National Tsing Hua University, Taiwan Micro Heat Pipes and Micro Heat Spreaders, G. P. "Bud" Peterson, Rensselaer Polytechnic Institute Microchannel Heat Sinks, Yitshak Zohar, Hong Kong University of Science and Technology Flow Control, Mohamed Gad-el-Hak, University of Notre Dame) Part IV: The Future Reactive Control for Skin-Friction Reduction, Haecheon Choi, Seoul National University Towards MEMS Autonomous Control of Free-Shear Flows, Ahmed Naguib, Michigan State University Fabrication Technologies for Nanoelectromechanical Systems, Gary H. Bernstein, Holly V. Goodson, and Gregory L. Snider, University of Notre Dame Index

The MEMS Handbook

Arrays of micrometer-scale needles could be used to deliver drugs, proteins, and particles across skin in a minimally invasive manner. We therefore developed microfabrication techniques for silicon, metal, and biodegradable polymer microneedle arrays having solid and hollow bores with tapered and beveled tips and feature sizes from 1 to 1,000 μm. When solid microneedles were used, skin permeability was increased in vitro by orders of magnitude for macromolecules and particles up to 50 nm in radius. Intracellular delivery of molecules into viable cells was also achieved with high efficiency. Hollow microneedles permitted flow of microliter quantities into skin in vivo, including microinjection of insulin to reduce blood glucose levels in diabetic rats.

/pdf/microfabricated-needles-for-transdermal-delivery-of-1j0yuh8xqv.pdf

Microfabricated needles for transdermal delivery of macromolecules and nanoparticles: Fabrication methods and transport studies

A review of microfluidic devices for cellomics is presented. After a brief description of the historical background of Lab-on-Chip (LOC) devices, different areas are reviewed. Devices for cell sampling are presented, followed by cell trapping and cell sorting devices based upon mechanical and electrical principles. Subsequently, a popular type of cell sorters, flow cytometers, is considered, followed by a chapter describing devices for cell treatment: cell lysis, poration/gene transfection and cell fusion devices. Finally a number of microfluidic devices for cellular studies are reviewed. The large amount of very recent publications treated in this review indicates the rapidly growing interest in this exciting application area of LOC.

/pdf/microfluidic-devices-for-cellomics-a-review-1hng9wltnz.pdf

Microfluidic devices for cellomics: a review

A bulk-micromachined multichannel silicon probe capable of selectively delivering chemicals at the cellular level as well as electrically recording from and stimulating neurons in vivo has been developed. The process buries multiple flow channels in the probe substrate, resulting in a hollow-core device, Microchannel formation requires only one mask in addition to those normally used for probe fabrication and is compatible with on-chip signal-processing circuitry. Flow in these microchannels has been studied theoretically and experimentally. For an effective channel diameter of 10 /spl mu/m, a channel length of 4 mm, and water as the injected fluid, the flow velocity at 11 torr is about 1.3 mm/s, delivering 100 pl in 1 s. Intermixing of chemicals, with the tissue fluid due to natural diffusion through the outlet orifice becomes significant for dwell times in excess of about 30 min, and a shutter is proposed for chronic use. The probe has been used for acute monitoring of the neural responses to various chemical stimuli in guinea pig superior and inferior colliculus.

A multichannel neural probe for selective chemical delivery at the cellular level

Microchannels for conducting and expelling a fluid are embedded in a surface of a silicon substrate. A channel seal is made of plural cross structures formed integrally with the silicon substrate. The cross structures are arranged sequentially over each channel, each cross structure having a chevron shape. The microchannel is sealed by oxidizing at least partially the cross structures, whereby the spaces therebetween are filled. A dielectric seal which overlies the thermally oxidized cross structures forms a complete seal and a substantially planar top surface to the silicon substrate. The dielectric seal is formed of a low pressure chemical vapor deposition (LPCVD) dielectric layer. The channel is useful in the production of an ink jet print in head, and has a polysilicon heater overlying the dielectric seal. A current passing through the heater causes a corresponding increase in the temperature of the ink in the microchannel, causing same to be expelled therefreom. After expulsion of the fluid, the microchannel is refilled by capillary action. Control circuitry, including bonding pads and sensors, can be formed integrally on the silicon substrate. In drug or chemical delivery systems, sensors and/or stimulation circuitry for sensing or inducing neural and other response can be formed directly in the silicon substrate which contains the microchannel. The sensor is disposed in close proximity to the chemical distribution nozzle, facilitating neural and other studies. Microvalve arrangements can be formed with the microchannel, controlled by the on-chip circuitry.

Microchannel system for fluid delivery

This paper describes a high-resolution monolithic nozzle array for inkjet printing. The nozzles are fabricated using a bulk anisotropic etching technology to undercut a network of highly-boron-doped silicon support ribs, forming an array of microchannels which are then sealed using thermal oxidation and LPCVD dielectrics. Closely-spaced trapezoidal or triangular nozzles are realized after cutting the wafer perpendicular to the microtubes. With a 21-/spl mu/m nozzle width and a 4-/spl mu/m nozzle-to-nozzle separation, a resolution of 1016 dots per inch (d/in) can be achieved. Polysilicon heaters are integrated on top of each microchannel so that when activated, the underlying ink is vaporized and a drop of ink is expelled to impinge on the paper. The fabrication of this device requires only five masks and is compatible with the addition of on-chip circuitry for multiplexing the heater control signals. Heat transfer efficiency to the ink is enhanced by the high thermal conductivity of the silicon ribs in the channel ceiling, while the bulk silicon maintains high interchannel isolation. Current pulses 20 /spl mu/s wide with a power density of 3.35/spl times/10/sup 8/ W/m/sup 2/ have been used in initial printing tests, resulting in 20-/spl mu/m diameter ink dots on a piece of paper which was set 2 mm away from the nozzle. The energy required to fire an ink drop is 11.5 /spl mu/J.

A high-resolution silicon monolithic nozzle array for inkjet printing

This paper describes a microheater structure and its integration on a silicon microprobe. The 30-/spl mu/m-diameter microstructure can be used to heat local areas of tissue or to measure local tissue temperature with an accuracy of <0.3/spl deg/C. The polysilicon microheater is suspended on a dielectric membrane to reduce undesired heat conduction to the probe substrate. The heating efficiency is 4.4/spl deg/C/mW in still water and 2.2/spl deg/C/mW in guinea pig cortex. Six milliwatts applied for 2 min in cortex produces a temperature of 50/spl deg/C, creating a well-defined 50-/spl mu/m-wide lesion for determining probe position histologically. Fabrication of the heaters requires no additional masking or processing steps in addition to those normally used for recording or stimulating probes.

Jingkuang Chen

Papers

A multichannel neural probe for selective chemical delivery at the cellular level

Microchannel system for fluid delivery

A high-resolution silicon monolithic nozzle array for inkjet printing

A silicon probe with integrated microheaters for thermal marking and monitoring of neural tissue