Past Projects

MicroSensors and MicroActuators Group > Past Projects
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Rapid, point-of-care diagnostic measurement of cytokines in vivo would advance patient care. A desirable approach to this measurement would be a transdermal or transvascular sensor fabricated in the shape of a needle, in which the sensing portion is formed on the needle tip and extends into the body medium of interest upon insertion. When contemplating the sensing approach for such a sensor, it is important to maintain a high degree of specificity to the protein of interest. Electronic-based sensing is a promising approach for femtomolar level specific detection of proteins due to its low cost, ease of miniaturization, and label-free operation. We’re developing a wafer-level microfabricated, needle-shaped impedance sensor for rapid, label-free detection of cytokines and other biomarkers. The sensor, consisting of a 20 μm x 20 μm micro-well array comprising 25 individual 2 μm-diameter wells embedded in a sensing tip, is lithographically configured on a laser micromachined fused silica needle. Label-free specific detection is achieved via functionalizing the microwells with antibody and monitoring the impedance change across the sensor electrodes due to the binding of target protein to the antibody.

Conference paper:

  1. N. Song, P. Xie, H. Oh, W. Shen, M. Javanmard and M. G. Allen, ” Wafer-Level Micromachining of Insertable, Label-free Cytokine Sensing Platforms”, BMES Annual Meeting, Philadelphia, USA, Oct. 2019.
  2. Song, P. Xie, M. Javanmard and M. G. Allen, “Microwell-array on a Flexible needle: a Transcutaneous Insertable Impedance Sensor for Label-Free Cytokine Detection”, MEMS 2018, Belfast, UK, Jan. 2018. (PDF).

Human brains are bottom-up synthesized machines that utilize highly complex networks of simple computational units i.e. neurons for cognitive processing. Artificial neural networks, which borrow aspects of this network topology, have already successfully demonstrated human-level classification performances in image and speech recognition tasks. However, implementing these networks on existing computer architectures with markedly different topologies leads to increased power consumption and sub-optimal operating speed. Recent efforts have evolved specialized transistor-based “neuromorphic” circuits that sacrifice the scalability of bottom-up fabrication technologies for the determinism of their top-down counterparts. In contrast, we are designing all-passive, transistor-free circuits that are amenable to the inherently stochastic but scalable bottom-up fabrication approaches. We are investigating the performance of these circuits on benchmark datasets and we are exploring simple fabrication techniques to realize them. The results of our research, we believe, will establish new methods for designing systems that embody intelligence at the physical level.    

Buried Interconnects

3-D Silicon Integration

Project Overview

Through-wafer interconnect technology, in which metal interconnections extend through a portion of the bulk silicon wafer, has gained noticeable research momentum in the field of integrated circuit (IC) fabrication, packaging, and micro-electro-mechanical systems (MEMS). In addition to the evident efficiency in utilizing the front and backside of the substrate, through-wafer interconnect provides compact packaging and many other advantages resulting from shorter connection distance compared to conventional interconnection technologies. Such characteristics as reduced total resistance, lower parasitics, reduced delay of signal, and low power consumption can be especially beneficial for radio-frequency (RF) and power devices. In collaboration with National Semiconductor, we are developing a new interconnect topoloy in which the through-wafer vias are shorter and copper circuitry is embedded within the unused volume of the silicon substrate.

In-Silicon Copper Circuitry

For the fabrication of buried interconnects, a combined silicon etch process and a spray coating process optimized for deep trenches were used. A simple bottom-up plating process was applied for the filling of through-wafer vias having reduced height of microns. The fabricated daisy-chain structure has been verified by cross-section observation of the final structure and electrical characterization. The proposed structure and fabrication process can be useful for applications that require through-wafer interconnection or wafer-level packaging that require integrated electrical interconnections. The unique approach of thick metallization inside deep vertical trenches and height control of the through-wafer via obviates the need for substrate lapping/polishing and secondary bonding processes, while maintaining a lower resistance of interconnects. A cross-sectional SEM view of a copper chain structure is shown in this image. The three different layers of electroplated copper structures are visible (light grey) and connected as designed, without any void formed in the via.
National Semiconductor

Publications

  1. C.-H. Ji, F. Herrault, P. Hopper, P. Smeys, P. Johnson, M.G. Allen, “Electroplated Metal Buried Interconnect and Through-Wafer Metal-Filled Via Technology for High-Power Integrated Electronics,” IEEE Transactions on Advanced Packaging, Vol. 32, Issue 3, pp. 695-702, Aug. 2009. (PDF)
  2. C.-H Ji, F. Herrault, and M.G. Allen, “A metallic buried interconnect process for through-wafer interconnection,” Journal of Micromechanics and Microengineering, v 18, n 7, p 085016 (10 pp.), Aug. 2008. (PDF)

Biodegradable Materials

Biomedical Implants

Project Overview

 
Biodegradable metallic and polymeric materials are typically sensitive to many standard chemicals used in microfabrication technologies. We are currently developing advanced fabrication approaches to augment the processing capabilities of such materials at the micro-scale.
 

Microfabricated Magnesium

 
 

Publications

  1. M. Tsang, F. Herrault, R.H. Shafer, and M.G. Allen, “Methods for the microfabrication of magnesium,” IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 347-350, Jan. 2013. (PDF)
  2. J.-H. Park, M.G. Allen, and M.R. Prausnitz, “Biodegradable polymer microneedles: fabrication, mechanics and transdermal drug delivery,” Journal of Controlled Release, 104:51-66, 2005. (PDF)

Collagen Microfibers

Advanced Microfabrication for Natural Materials

Project Overview

Emerging biomaterials based upon analogues of native extracellular matrix proteins provide an opportunity to create protein scaffolds that mimic tissue mechanical behavior and guide cellular responses. However, in order to reproduce macroscale tissue properties, protein analogues must be endowed with appropriate microstructural features. In particular, the crimped or wavy microstructure of native collagen fibers, with a periodicity of 10 – 200 mm, contributes in a significant manner to the compliance, strength, and durability of soft tissues.

IProtein-Based Micro/Nano Fibers

We developed a template-based technique for the fabrication of polymer micro/nanofiber composites, exercising control over the fiber dimensions and alignment. Unlike conventional spinning-based methods of fiber production, the presented approach is based on micro-transfer molding. It is a parallel processing technique capable of producing fibers with control over both in-plane and out-of-plane geometries, in addition to packing density and layout of the fibers. Collagen has been used as a test polymer to demonstrate the concept. Hollow and solid collagen fibers with various spatial layouts have been fabricated. Produced fibers have widths ranging from 2 to 50 microns, and fiber thicknesses ranging from 300 to 3000 nm. Also, three-dimensionality of the process has been demonstrated by producing in-plane serpentine fibers with designed arc lengths, out-of-plane wavy fibers, fibers with focalized particle encapsulation, and porous fibers with desired periodicity and pore sizes.

 

Publications

 
  1. J.M. Caves, V.A. Kumar, W. Xu, N. Naik, M.G. Allen, and E.L. Chaikof, “Microcrimped collagen fiber-elastin composites,” Advanced Materials, v 22, n 18, p 2041-2044, May 2010. (PDF)
  2. N. Naik, J. Caves,V. Kumar,E. Chaikof, and M.G. Allen, “A template-based fabrication technique for spatially-designed polymer micro/nanofiber composites,” Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS 2009), pp. 1869-1872, June 2009. (PDF)
 
 

Lamination Technologies

Advanced Microfabrication

Project Overview

 
Many nanomanufacturing approaches can be classified into two categories: precisely-controlled assembly approaches that rely on nano-scale manipulation techniques (e.g., AFM or e-beam lithography), and volumetric chemical syntheses (e.g., emulsion-based production of nanoparticles). The former approach has the advantage of exquisite control of the location and structure of the fabricated nanostructures, but is typically restricted to a surface patterned via serial processes. The latter approach allows larger volumes of nanostructures to be realized, at the expense of the exquisite control of the former. We are devoting efforts in electroplating-based volumetric nanomanufacturing to create highly-structured multilayer metallic materials, with precisely designed characteristic lengths in the hundreds of nanometers but volumes of manufactured material in the macro range. This electroplating-based approach also enables batch fabrication of nanostructures, combining the advantages of precisely-controlled assembly approaches and nano-scale manipulation techniques.

 

 

 

Microfabricated Laminations

 

In order to create a multilayer structure with sub-micron characteristic lengths, alternating layers of two or more metals are sequentially electroplated through a standard photoresist mold defined using photolithography techniques. The figure shows a conceptual rendering of the robotically-assisted electroplating setup. By automatically alternating the plating materials and controlling the electrodeposition time and current density, it is possible to create a thick (several hundreds of microns) structure that consists of sub-micron-thick layers of metallic materials. Post-electrodeposition, one or more metals are selectively etched away, creating a scaffold consisting of high-lateral-aspect-ratio metallic films. The metallic layers can be supported by metallic or polymer posts depending on the targeted application. For example, in highly-laminated magnetic cores, the layers must be electrically insulated from each other to efficiently reduce eddy current losses, preventing the use of metallic posts. Conceptually, this approach solely relies on established large area microfabrication techniques such as electroplating and chemical etching to develop a nanostructured material with improved performance.

 

 

 
 

Publications

 
  1. J. Kim, M. Kim, P. Galle, F. Herrault, R. Shafer, J.Y. Park, and M.G. Allen, “Nanolaminated permalloy core for high-flux high-frequency ultracompact power conversion,” Transactions on Power Electronics,v 28, n 9, p 4376-4383, Sept. 2013. (PDF)
  2. M. Kim, F. Herrault, J. Kim, J.K. Kim, and M.G. Allen, “Monolithically-fabricated laminated inductors with electrodeposited silver windings,” IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 873-876, Jan. 2013. (PDF)
  3. A. Armutlulu, Y. Fang, S.H. Kim, C.H. Ji, S.A. Bidstrup Allen, and M.G. Allen, ” A MEMS-enabled 3D zinc-air microbattery with improved discharge characteristics based on a multilayer metallic substructure,” Journal of Micromechanics and Microengineering, v 21, n 10, Oct. 2011. (PDF)
  4. F. Herrault, W.P. Galle, R.H. Shafer, and M.G. Allen, “Electroplating-based approaches for volumetric nanomanufacturing,” Technologies for Future Micro-Nano Manufacturing, Aug. 2011. (PDF)
  5. W.P. Galle, S.-H. Kim, U. Shah, and M.G. Allen, “Micromachined capacitors based on sequential multilayer electroplating,” 23nd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010), Jan. 2010. (PDF)
  6. A. Armutlulu, Y. Fang, S.-H. Kim, C.-H. Ji, S.A. B. Allen, and M.G. Allen, “High-current Zn-Air microbattery based on a micromachined multilayer lateral metallic scaffold,” 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2010), p 107-110, 2010. (PDF)
 
 
 
 

Metal Transfer Micromolding

Advanced Microfabrication

Project Overview

Electrically and biologically functional 3-D microstructures have a wide range of potential applications in biomedical, chemical, physical, and electronic areas. One way to implement these microstructures is to use non-conducting materials such as polymer or ceramic for structural fabrication, and use electrically conducting materials such as metal, conductive polymer, conductive oxide etc. for layer deposition and patterning, which will allow the device to have electrical functionality. As a result, we developed MEMS-based molding fabrication technologies to create 3-D metallic and polymeric structures.

MTM Process

A three-dimensional (3-D) metal transfer micromolding (MTM) fabrication process for manufacturable, high-aspect- ratio MEMS structures with a patterned metal layer for electrical and biological functionalities has been developed. The mechanism of MTM lies in the differences in adhesion strengths between mold-metal and replica-metal interfaces. This is an extension of a non-covalent 2-D nanotransfer printing (nTP) process and enables a simultaneous replication of high-aspect-ratio 3-D structures from a mold in a single polymer molding process. The conductive layer is patterned at this same step, enabling the resulting structure to have a patterned electrically/biologically functional 3-D metallic layer defined on the high-aspect-ratio polymer structure. This metallic layer on the polymer device has been utilized as a bio-compatible site for cell culturing, an electrode for spontaneous recording from cells and for RF MEMS functionalities. Thus combining the virtues of a conventional micromolding process such as the large-area, high-throughput, and low-cost with simultaneous transfer of patterned metal layer, the MTM process can be applied to a wide range of applications in the chemical, high-frequency, and biomedical areas.
 

Publications

 
  1. S. Rajaraman, S.-O. Choi, M.A. McClain, J.D. Ross, M.C. LaPlaca, and M.G. Allen, “Metal-transfer-micromolded three-dimensional microelectrode arrays for in-vitro brain-slice recordings,” Journal of Microelectromechanical Systems, v 20, n 2, p 396-409, April 2011. (PDF)
  2. Y. Zhao, Y.K. Yoon, S.O. Choi, X. Wu, Z. Liu, and M.G. Allen, “Three dimensional metal pattern transfer for replica molded microstructures,” Applied Physics Letters, vol. 94, no. 2, 023301, 2009. (PDF)
  3. S. Rajaraman, Y. Zhao, X. Wu, S.-H. Kim, and M.G. Allen, “Metal transfer micromolding (MTM) process for high-aspect-ratio 3-D structures with functional metal surfaces,” International Symposium on Flexible Automation (ISFA 2008), Atlanta, USA, June 2008. (PDF)
  4. S. Rajaraman, M.A. McClain, S.-O Choi, J.D. Ross, S.P. DeWeerth, M.C. LaPlaca, and M.G. Allen, “Three-dimensional metal transfer micromolded microelectrode arrays (MEAS) for in-vitro brain slice recordings,” Transducers 2007: The 14th International Conference on Solid-State Sensors, Actuators and Microsystems, pp.1251-1254, Lyon, France, June 2007. (PDF)
  5. Y. Zhao, Y.-K. Yoon, X. Wu, and M.G. Allen, “Metal-transfer-micromolding of air-lifted RF components,” Transducers 2007: The 14th International Conference on Solid-State Sensors, Actuators and Microsystems, Lyon, France, June 2007. (PDF)
  6. Y. Zhao, Y.-K. Yoon, and M.G. Allen, “Metal-transfer-micromolded RF components for System-On-Package (SOP),” 57 Electronic Components and Technology Conference (ECTC ’07), 2007. (PDF)
  7. S-O. Choi, S. Rajaraman, Y-K. Yoon, X. Wu, and M.G. Allen, “3-D metal patterned microstructure using inclined UV exposure and metal transfer micromolding technology,” Solid-State Sensor, Actuator, and Microsystems Workshop (Hilton Head 2006), June 2006. (PDF)
  8. X. Wu, Y. Zhao, Y.-K. Yoon, S.-O Choi, J.-H. Park and M.G. Allen, “Enhanced wettability polymer micromolding by a 3-D metal transfer process,” ACS conference, March 2006. (PDF)

 

UV-LED Lithography

Microfabrication technologies

Project Overview

 
UV lithography systems based on mercury lamp sources have traditionally been used in micro/nano patterning. Modifications of these basic systems, such as deep UV lithography and addition of UV filters, can further enhance fine resolution patterning. In MEMS, mercury-lamp-based UV lithography has been further extended to encompass unconventional methods including thermal reflow processes, multidirectional UV lithography, diffuser lithography, and timed-development and-thermal-reflow process. Recent advances in light emitting diode technology have resulted in LEDs that emit in the near ultraviolet. Such UV-LEDs have been used not only in conventional applications and sterilization, but also as a microfabrication tool. Examples include a single UV-LED for direct write lithography, and an array of LEDs in which the spatially nonuniform emission of the LEDs was exploited for microlens array fabrication. Since the UV-LED has the advantages of simple operation and relatively low cost, yet produces high quality near-monochromatic light, it shows great potential for use in microfabrication.

UV-LED Performance Evaluation

UV lithography based on an array of UV-LEDs for conventional and three-dimensional exposure of thin and thick photoresists has been developed. The UV-LED approach shows the ability to create structures comparable to those from conventional mercury lamp sources with comparable exposure times (see published paper for comparison results). Further, the UV-LED approach has several advantages including simplicity of operation, low power consumption, and reduced system cost. Typical thicknesses of SU-8 resist, namely 15, 50, 70, and 100 ?m, were successfully patterned. The UV-LED approach has also been successfully demonstrated in advanced 3-D lithography, including single and multiple static inclined exposure and dynamic exposure schemes, and timed-development-and-thermal-reflow process. Additional work to create complex polymer microstructures via a combination of inclined rotational lithography technique and UV-LED exposure tool is currently under investigation.
 
 

Publications

 
  1. J.K. Kim, S.J. Paik, F. Herrault, and M.G. Allen, “UV-LED lithography for 3-D high aspect ratio microstructure patterning,” 14th Solid State Sensors, Actuators, and Microsystems Workshop, p 481-484, June 2012. (PDF)
  2. J.K. Kim, M.G. Allen, and Y.-K. Yoon, “Computer controlled dynamic mode multidirectional UV lithography for 3-D microfabrication,” Journal of Micromechanics and Microengineering, v 21, n 3, p 035003, March 2011. (PDF)
 
 
 
 

Biodegradable Sensors

Biomedical Implants

Project Overview

 
Implantable resonant passive sensors were proposed more than five decades ago as a solution to wirelessly measure physical parameters in vivo. Since then, non-degradable MEMS-fabricated passive resonant sensors have been demonstrated for chronic implantable applications to monitor blood pressure and other physiological conditions. Although such sensors show great promise for chronic applications, some acute or shorter-term medical applications (e.g., wound or bone healing) could also benefit from implantable monitoring sensors. Typically these sensors should be extracted when no longer needed. In these applications, if instead the sensor could be made completely biodegradable, this extraction could be avoided.

 

 

 

Biodegradable Pressure Sensors

We are developing wireless RF pressure sensor made entirely of biodegradable materials and fabricated via MEMS technologies. The sensor utilizes RF interrogation while simultaneously maintaining its all-biodegradable character. The pressure sensor consists of a sensing cavity, bounded by two electrodes forming the variable capacitor and connected in series with an inductor coil. The inductor coil not only acts as an essential component of the resonant sensor, but also provides means for magnetically coupling the sensor to an external (e.g., outside the body) coil. When pressure is applied to the sensor, the gap between the two capacitive electrodes is reduced and the capacitor value increases. The resulting pressure-induced change in the LC resonant frequency can be measured wirelessly using the external coil. Metallic zinc, known to be biocompatible, was also found to be degradable in saline and was subsequently used as the sensor conductor material, while biodegradable polymers (PLA and PCL) were used as dielectrics and structural materials. Alternative MEMS fabrication approaches using embossing and multi-layer folding were combined with traditional techniques to fabricate the pressure sensor. Experimentally, the fabricated sensor (shown in this image) made of biodegradable materials demonstrated linear frequency response with external applied pressure. A sensitivity of – 290 kHz/kPa was measured in the 0-30 kPa pressure range.
 
 
 

Publications

  1. M. Luo, C. Song, F. Herrault, and M.G. Allen, “A microfabricated RF wireless pressure sensor made completely of biodegradable materials,” 14th Solid State Sensors, Actuators, and Microsystems Workshop, p 38-41, June 2012. (PDF)
 

MEMS-based batteries

Energy Storage

Project Overview

Currently, there is a growing need for energy storage devices, both micro- and macroscale, that are expected to have the capability of rapid charge and discharge rates with a minimum loss in energy storage. Conventional batteries possess high energy density enabling them to supply energy to systems for long periods of time, yet often lack similarly high power density resulting in limited energy transfer rates. Supercapacitors, on the other hand, are capable of very fast charge and discharge rates due to their extremely high power density; however, the amount of energy they can store is quite low compared to their battery counterparts. To bridge the application gap between these two energy storage mechanisms, batteries with rapid charge and discharge capabilities are required.
 

Microfabricated High-Surface-Area Batteries

We have designed and fabricated ordered, high-surface-area, three-dimensional microstructures (see photo). The primary application is for current collectors for the electrochemically active material of corresponding energy storage devices. The microstructures are fabricated through sequential electroplating of sacrificial and structural layers in a photoresist mold, followed by selective removal of the sacrificial layers (see “Lamination Technologies” research page). Nickel oxyhydroxide (NiOOH) was chosen as a secondary battery chemistry and deposited on the MEMS-enabled microstructures, forming functional electrodes for electrochemical energy storage devices. The electrodes are tested by charging and discharging galvanostatically at various rates ranging from 2 C to 120 C where x-C is the rate of complete charge or discharge for 1/x hours. It was shown that the electrode was able to retain 90 % of its capacity at a charge rate of 120 C.
 

Publications

  1. A. Armutlulu, S.A. Bidstrup Allen, and M.G. Allen, “3D microstructures for fast charge and discharge batteries,” PowerMEMS 2012, p 203-206, Dec. 2012. (PDF)
  2. J.K. Kim, A. Armutlulu, M. Kim, S. Paik, S.A. Bidstrup Allen, and M.G. Allen “A fabric-based Ni-Zn battery using a microfiber substrate and separator,” PowerMEMS 2012, p , Dec. 2012. (PDF)
  3. A. Armutlulu, Y. Fang, S.H. Kim, C.H. Ji, S.A. Bidstrup Allen, and M.G. Allen, ” A MEMS-enabled 3D zinc-air microbattery with improved discharge characteristics based on a multilayer metallic substructure,” Journal of Micromechanics and Microengineering, v 21, n 10, Oct. 2011. (PDF)
  4. A. Armutlulu, Y. Fang, S.-H. Kim, C.-H. Ji, S.A. B. Allen, and M.G. Allen, “High-current Zn-Air microbattery based on a micromachined multilayer lateral metallic scaffold,” 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2010), p 107-110, 2010. (PDF)
 
 
 
 

Air-Flow Sensors

Flight Control Applications

Project Overview

Flow sensors are of paramount importance in flight control applications involving unmanned aerial vehicles (UAVs). They essentially consist of out-of-plane structures, such as artificial cilia, or in-plane shear stress sensors. Most of these devices are fabricated using silicon, which limits the achievable height of the cilia to well below the boundary layer thickness. This gives little or no information about the flow fluctuations in the main stream. The design of our sensors is based on the wind receptor hair in insects. Air flow around the hair causes a drag force induced deflection, which in turn activates a sensory response, providing the insect with information about variations in the local flow field.

 

Piezoresistive Air-Flow Sensors

We developed out-of-plane micromachined piezoresistive flow sensor arrays based on laser micromachining of polymer films, microstencil printing, and stress-engineered curvature. The developed process is suitable for low cost, large-area sensor array fabrication, and can leverage traditional flex-circuit fabrication. Each device is composed of an out-of-plane curved microtuft
formed from laser-machined polyimide and PECVD-deposited silicon dioxide, and a conductive elastomer piezoresistor with a measured gage factor of 7.3 located at the base of the microtuft. The fabrication sequence also enables backside interconnects without adding further process complexity, which facilitates integration and enables the sensing of airflow with minimum interference due to the sensing circuitry. Individual microtufts as small as 1.5 mm in length and 0.4 mm in width, with 70-micron-wide piezoresistor lines have been fabricated, and operation has been demonstrated in wind tunnel.
 

Publications

  1. C. Song, A.R. Aiyar, S.-H. Kim, and M.G. Allen, “Exploitation of aeroelastic effects for drift reduction, in an all-polymer air flow sensor,” Sensors and Actuator: A Physical, v 165, n 1, p 66-72, Jan. 2011. (PDF)
  2. A.R. Aiyar, C. Song, S.-H. Kim and M. G. Allen, “An all-polymer air-flow sensor array using a piezoresistive composite elastomer,” Smart Materials and Structures, 18, 115002, 2009. (PDF)
  3. C. Song, A. R. Aiyar, S.-H. Kim, and M.G. Allen, “Exploitation of aeroelastic effects for drift reduction in an all-polymer air flow sensor,” Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS 2009), pp. 1545-1548, June 2009. (PDF)
  4. A. Aiyar, C. Song, S.-H. Kim, and M.G. Allen, “An all polymer air-flow sensor array using a piezoresistive composite elastomer,” 22nd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2009), pp. 447-451, Jan. 2009. (PDF)

 

Microneedle Patch

 

Project Overview

 
The Georgia Institute of Technology, Kwangwoon University, South Korea, and Infopia, South Korea, have teamed up to develop a wireless-continuous glucose self-monitoring system using micro/nano fusion technology for the application of ubiquitous health life. The achievement of the proposed goals will leverage realization of a smart u-healthcare service, consisting of sensing in normal life; monitoring and wireless communication; and analysis and diagnosis. The system is intended to increase ease of use of glucose monitoring. The key competitive approach is to increase the ease of use of these monitors by improving non-invasiveness, increase the duration of sensor efficacy, and enable automatic measurement without patient intervention. Ultimately, these devices will result in improved patient compliance as well as provide a key competitive advantage for the developed technologies over existing approaches. This project is funded by the Korea Institute for Advancement of Technology (KIAT) of the Ministry of Knowledge Economy (MKE), Republic of Korea, under the International Collaborative R&D program.

 

 

 

Microneedle Patch

 

We are working towards developing a technology for the painless, self-monitoring of blood glucose concentrations using a patch-type smart microneedle module. The system consists of a patch-type smart microneedle module with integration of minimally-invasive microneedles and micro/nano porous sensing microelectrodes; and a handheld monitor module that remotely receives sensing results and analyzes the data. A 3-D microstructure with sharp tip end and high aspect ratio penetrates skin in a minimally invasive manner, and micro/nano porous sensing microelectrodes detect glucose molecules in the body. The 3-D microneedle structure and isolated microelectrodes are fabricated at Georgia Tech and are integrated with micro/nano porous electrodes developed in collaboration with Kwangwoon University.

Collaboration: Kwangwoon University, South Korea, and Infopia, South Korea

Sponsor: Korea Institute for Advancement of Technology (KIAT)

 
 

Publications

Small-Scale Reed Actuators

Heat Transfer Enhancement Technology

Project Overview

As electronic system technology advances � with continual increases in requirements leading to increasing demand for higher power consumption � there has been increasing pressure on the thermal engineering and heat rejection technologies used. Many systems are driving conflicting needs for high performance as well as reduced size and weight. While new technologies improve performance or reduce size and weight of the systems, the power consumption of these systems often increases with each improvement. As a result, the performance of the heat rejection technology has become a dominant limitation in many applications. We worked in collaboration with Pr. A. Glezer’s research group at Georgia Tech and United Technology Research Center towards d. This project was funded by the DARPA MACE program.
 
Flow-Powered Passive Reed Actuators

Publications

  1. F. Herrault, P.A. Hidalgo, C.-H. Ji, A. Glezer, and M.G. Allen, “Cooling performance of micromachined self-oscillating reed actuators in heat transfer channels with integrated diagnostics,” IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 1217-1220, Jan. 2012. (PDF)
  2. P. Hidalgo, F. Herrault, A. Glezer, M.G. Allen, S. Kaslusky, and B. S.Rock, “Heat transfer enhancement in high-power heat sinks using active reed technology,” 16th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), Page(s): 1-6, v 19, Oct. 2010. (PDF)

Silicon Nanoneedles

Intracellular Drug Delivery

Project Overview

 
Investigation into cellular functions requires the ability to apply specific and controlled treatment to cells. Such treatment includes the delivery of biological effectors across cell membranes using various approaches such as chemical, mechanical or electrical perturbations to cells. In addition to investigation, gene correction represents an active treatment in which genetic diseases and cancer may be treated by correcting the causative mutations in the genetic code. For example, sickle cell disease is the most common inherited blood disorder caused by a mutation of a single nucleotide of a gene. The disease can be alleviated by transforming defective blood-forming cells into normal ones by inserting corrective genes. As a result, we are developing, in collaboration with the Laboratory for Drug Delivery at Georgia Tech, nanoneedles for intracellular drug delivery. This project is funded by the National Institute of Health (NIH).T


 

Micromachined Silicon Nanoneedles

 

We are working, in collaboration with researchers of Dr. M.R. Prausnitz’s research group at Georgia Tech, towards developing highly-dense needle arrays with sharp nano-tips for intracellular gene and drug delivery, with the ultimate goal of gene correction in a high-throughput manner. The nanoneedles are fabricated using silicon micromachining technology including isotropic dry etching, anisotropic dry etching and thermal-oxidation-based tip sharpening. The silicon nanoneedle array with needle tip diameters in tens of nanometers enables pinpoint injection of individual cells in a high throughput manner without causing cell death by puncture. The image shows a dense array of such silicon needles with nano-tips. In-vitro intracellular delivery tests demonstrate that the nanoneedle array can effectively deliver molecular probes into cells by cell membrane penetration.


Collaboration: Laboratory for Drug Delivery – Pr. M. Prausnitz – Georgia Tech

Sponsor: National Institute of Health (NIH)

 

Publications

  1. S.J. Paik, S. Park, V. Zamitsyn, S. Choi, X. Guo, M. Prausnitz, and M.G. Allen, “A highly dense nanoneedle array for intracellular gene delivery,” 14th Solid State Sensors, Actuators, and Microsystems Workshop, p 149-152, June 2012. (PDF)

Elastomeric Microelectrodes

Neural Recordings

Project Overview

Conventional neuroelectrodes have a bulk conductive metal core that makes them much stiffer than the tissue from which they record or stimulate. The difference in mechanical properties causes chronic microtrauama and presents difficulties for conformal contact with irregular features. Using advanced microfabrication technologies, we aim to develop flexible microelectrodes for neural recordings.

 

Highly-Compliant Microcable Neuroelectrodes

We develop a fabrication process flow for arrays of electrically functional, elastomer microcables. Elastomeric electronics is generally comprised of an elastomer that integrates an electrical conductor in some fashion, commonly by mixing conductive particulates into the bulk elastomer. Using bulk electrically conductive elastomers in micropatterned devices presents challenges in controlled, precise patterning of the conductive media and in incorporating the conductive component with selectively insulated and exposed regions. Thin-film gold metallization of silicone rubber addresses these considerations as gold is frequently patterned in microfabricated devices and silicone can tolerate some but not all standard process techniques. Gold has relatively soft and non-brittle mechanical properties, which are advantageous for use in elastomer electronics. It also does not form a surface oxide, making it suitable for features such as the electrical access nodes for this application. PDMS shape and topography is being defined using a spun-cast micromolding technology.

Publications

  1. M.A. McClain, I.P. Clements, R.H. Shafer, R.V. Bellamkonda, M.C. Laplaca, and M.G. Allen, “Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS,” Biomedical Microdevices, v 13, n 2, p 361-373, April 2011. (PDF)
  2. M.A. McClain, M.C. LaPlaca, and M.G. Allen, “Spun-cast micromolding for etchless micropatterning of electrically functional PDMS structures,” Journal of Micromechanics and Microengineering, v 19, n 10, p 107002 (6 pp.), Oct. 2009. (PDF)
  3. M. McClain, M. C LaPlaca, and M.G. Allen, “An integrated elastomer mesh and microelectrode array for neurophysiology,” Georgia Life Sciences Summit, September 2008.
  4. M.A. McClain, M.C. LaPlaca, and M.G. Allen, “The development of strand-like microelectrode arrays for in vitro neuron culture,” Society for Neuroscience, Nov. 2007.

Air-Core Inductors

Power Supply on a Chip

Project Overview

Today’s power converters are large and inefficient because they are based on decades-old technologies and rely on expensive, bulky, and failure-prone components. Within the next 20 years, 80% of the electricity used in the U.S. will flow through these devices, so there is a critical need to improve their size and efficiency. MIT is teaming with Georgia Institute of Technology, Dartmouth College, and the University of Pennsylvania (UPenn) to create more efficient power circuits for energy-efficient light-emitting diodes (LEDs) through advances in 3 related areas. First, the team is using semiconductors made of high-performing gallium nitride grown on a low-cost silicon base (GaN-on-Si). These GaN-on-Si semiconductors conduct electricity more efficiently than traditional silicon semiconductors. Second, the team is developing new magnetic materials and structures to reduce the size and increase the efficiency of an important LED power component, the inductor. This advancement is important because magnetics are the largest and most expensive part of a circuit. Finally, the team is creating an entirely new circuit design to optimize the performance of the new semiconductors and magnetic devices it is using. This project is funded by the ARPA-e ADEPT program.

Microfabricated Air-Core Inductors

Air-core magnetics offer the advantage of avoiding the high losses most ferromagnetic materials contribute at very high frequencies. Although some air-core designs have high winding losses and produce external magnetic fields that are a liability for electromagnetic interference and induced power losses in nearby materials, toroidal configurations can be self shielding and can be designed for low losses. We are working towards two approaches: 1. Microfabricated air-core inductors on low-loss substrates; and 2. Silicon-embedded inductors. The collage shows various 3-D microfabricated inductors with inductances ranging from 0.05 to 0.7 uH. The inductor designs are compatible with flip-chip bonding technologies for integrated PowerSoc. In collaboration with MIT, Dartmouth college, and UPenn, we are currently evaluating these inductors in high-voltage high-frequency circuits.

Collaboration: MIT

Sponsor: ARPA-e

 
 

Publications

 
  1. X. Yu, M. Kim, F. Herrault, C.-H. Ji, J. Kim, and M.G. Allen, “Silicon-embedding approaches to 3-D toroidal inductor fabrication,” Journal of Microelectromechanical Systems, in press.
  2. M. Araghchini, J. Chen, V. Doan-Nguyen, D.V. Harburg, D. Jin, J. Kim, M. Kim, S. Lim, B. Lu, D. Piedra, J. Qiu, J. Ranson, M. Sun, X. Yu, H. Yun, M.G. Allen, J.A. del Alamo, G. DesGroseilliers, F. Herrault, J.H. Lang, C.G. Levey, C.B. Murray, D. Otten, T. Palacios, D.J. Perreault, and C.R. Sullivan, “A technology overview of the powerchip development program,” Transactions on Power Electronics,v 28, n 9, p 4182-4201, Sept. 2013. (PDF)
  3. J.K. Kim, F. Herrault, X. Yu, M. Kim, R.H. Shafer, and M.G. Allen, “Microfabrication of air core inductors with metal-encapsulated polymer vias,” Journal of Micromechanics and Microengineering, v 23, n 3, p 035006 (7 pp.), March 2013. (PDF)
  4. J.K. Kim, F. Herrault, X. Yu, and M.G. Allen, “Microfabrication of air-core toroidal inductor with very high aspect ratio metal-encapsulated polymer vias,” PowerMEMS 2012, p 30-33, Dec. 2012. (PDF)
  5. X. Yu, M. Araghchini, F. Herrault, J.K. Kim. J.H. Lang, and M.G. Allen, “Fabrication, modeling and performance analysis of silicon-embedded 3-D toroidal inductors,” PowerMEMS 2012, p 58-61, Dec. 2012. (PDF)
  6. M. Araghchini, M. Kim, X. Yu, F. Herrault, M.G. Allen, and J.H. Lang, “Modeling and measured verification of loss in MEMS toroidal inductors,” IEEE Energy Conversion Congress and Exposition (ECCE), p 3293-3300, Sept. 2012. (PDF)
  7. D.V. Harburg, X. Yu, F. Herrault, C.G. Levey, M.G. Allen, and C.R. Sullivan, “Micro-fabricated thin-film inductors for on-chip power conversion,” 2012 7th International Conference on Integrated Power Electronics Systems (CIPS), p. 6ff, March 2012. (PDF)
  8. X. Yu, M.S. Kim, F. Herrault, C.-H. Ji, J.K. Kim, and M.G. Allen, “Silicon-embedded 3D toroidal air-core inductor with through-wafer interconnect for on-chip integration,” IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 325-328, Jan. 2012. (PDF)
  9. Y.-K. Yoon, J.-W. Park, and M.G. Allen, “Polymer-core conductor approaches for RF MEMS” Journal of Microelectromechanical Systems, v. 14, n. 5, Oct, 2005. (PDF)

Laminated Metallic Magnetic Cores

Power Supply on a Chip

Project Overview

 
We are working in collaboration with Texas Instruments towards creating compact, low-profile power adapters and power bricks using materials and tools adapted from other industries and from grid-scale power applications. Adapters and bricks convert electrical energy into useable power for many types of electronic devices, including laptop computers and mobile phones. These converters are often called wall warts because they are big, bulky, and sometimes cover up an adjacent wall socket that could be used to power another electronic device. The magnetic components traditionally used to make adapters and bricks have reached their limits; they cannot be made any smaller without sacrificing performance. In this research project, we are taking a cue from grid-scale power converters that use iron alloys as magnetic cores. These low-cost alloys can handle more power than other materials, but the iron must be stacked in insulated plates to maximize energy efficiency. In order to create compact, low-profile power adapters and bricks, these stacked iron plates must be extremely thin, only hundreds of nanometers in thickness, in fact. To make plates this thin, we are using manufacturing tools used in microelectromechanics and other small-scale industries. This project is funded by the ARPA-e ADEPT program.
 

Laminated Metallic Magnetic Cores

Collaboration: Texas Instruments

Sponsor: ARPA-e

 
 

Publications

 
  1. J. Kim, M. Kim, P. Galle, F. Herrault, R. Shafer, J.Y. Park, and M.G. Allen, “Nanolaminated permalloy core for high-flux high-frequency ultracompact power conversion,” Transactions on Power Electronics,v 28, n 9, p 4376-4383, Sept. 2013. (PDF)
  2. M. Kim, F. Herrault, J. Kim, J.K. Kim, and M.G. Allen, “Monolithically-fabricated laminated inductors with electrodeposited silver windings,” IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 873-876, Jan. 2013. (PDF)
  3. J. Kim, J.K. Kim, M. Kim, F. Herrault, and M.G. Allen, “Integrated toroidal inductors with nanolaminated metallic magnetic cores,” PowerMEMS 2012, p 18-21, Dec. 2012. (PDF)
  4. F. Herrault, W.P. Galle, R.H. Shafer, and M.G. Allen, “Electroplating-based approaches for volumetric nanomanufacturing,” Technologies for Future Micro-Nano Manufacturing, Aug. 2011. (PDF)
  5. W.P. Galle, S.-H. Kim, U. Shah, and M.G. Allen, “Micromachined capacitors based on sequential multilayer electroplating,” 23nd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010), Jan. 2010. (PDF)
  6. P. Galle, X. Wu, L. Milner, S.-H. Kim, P. Johnson, P. Smeys, P. Hopper, K. Hwang, and M.G. Allen, “Ultra-compact power conversion based on a CMOS-compatible microfabricated power inductor with minimized core losses,” 57 Electronic Components and Technology Conference (ECTC ’07), 2007. (PDF)
  7. J.-W. Park, F. Cros, and M.G. Allen, “Planar spiral inductors with multilayer micrometer-scale laminated cores for compact-packaging power converter applications,” IEEE Transactions on Magnetics, v 40, no. 4, July 2004. (PDF)
  8. J.-W. Park, and M.G. Allen, “Ultra low-profile micromachined power Inductors with highly laminated Ni/Fe cores: Application to low-megahertz DC-DC converters,” IEEE Transactions on Magnectics, vol. 39, no. 5, pp. 3184-3186, Sept. 2003. (PDF)
  9. J.W. Park, J. Park, Y.-H. Joung, and M.G. Allen, “Fabrication of high current and low profile micromachined inductor with laminated Ni/Fe core,” IEEE Transactions on Components and Packaging Technologies, vol. 25, no. 1, p. 106-111, 2002. (PDF)
  10. J.-W. Park, F. Cros, and M.G. Allen, “A sacrificial layer approach to highly laminated magnetic cores,” 15th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p.380-3, 2002. (PDF)

Microfabricated Permanent-Magnet Arrays

Small-Scale Undulators for X-Ray Generation

Project Overview

 
We are working towards developing technologies for microscale permanent-magnet fabrication and magnetic patterning, with a focus on realizing magnetic undulators with high spatial field gradient distrubution. Magnetic undulators are one major component of most x-ray sources. By reducing the undulator period using MEMS technologies, while maintaining high magnetic field strengths, our approach will not only reduce the physical undulator size, but more importantly enable the efficient generation of brilliant, high-energy (>10 keV), mono-energetic x-rays from modest electron beam energies (~200 MeV). Currently, x-ray radiation required for accomplishing phase-contrast imaging can be generated only using large synchrotrons. Recent advances in accelerator and laser technologies suggest they might be exploited to enable much less expensive and smaller x-ray sources. This project is funded by the DARPA AXiS program.

 

 

 

Laser-Micromachined Permanent Magnets

 

Many MEMS systems can benefit from dense, alternating arrays of permanent magnets (PM) with high energy-product and substantial magnetic flux density adjacent to the array. In this work, we demonstrate laser machining fabrication and assembly techniques to create linear PM alternating arrays with periods as low as 230 microns. Comb-shaped magnet structures are micromachined from a 300 micron thick samarium cobalt (SmCo) substrate using an IR laser. These structures are then magnetized and assembled in an interlocking fashion to make alternating magnet arrays of various total lengths. Scanning Hall-effect sensor measurements taken 80 microns above the surface indicate sinusoidally varying magnetic fields with periods as expected from the underlying magnet geometry and peak magnetic flux density amplitudes of 0.1 T.

 

Collaboration: Pr. D. Arnold’s research group at the University of Florida

Sponsor: DARPA

 
 

Publications

 
  1. B.A. Peterson, W.C. Patterson, F. Herrault, D.P. Arnold, and M.G. Allen, “Laser-micromachined permanent magnet arrays with spatially alternating magnetic field distribution,” PowerMEMS 2012, p 319-322, Dec. 2012. (PDF)
  2. B.A. Peterson, F. Herrault, O.D. Oniku, Z.A. Kaufman, D.P. Arnold, and M.G. Allen, “Assessment of laser-induced damage in laser-micromachined rare-earth permanent magnets at the sub-millimeter scale,” IEEE Transactions on Magnetics, v 48, n 11, p 3606-9, Nov. 2012. (PDF)
  3. B.A. Peterson, F. Herrault, O.D. Oniku, Z.A. Kaufman, D.P. Arnold, and M.G. Allen, “Assessment of laser-induced damage in laser-micromachined rare-earth permanent magnets at the sub-millimeter scale,” Intermag 2012, May 2012.
 
 
 
 

Polymer Microneedles

Transdermal Drug Delivery

Project Overview

 
The Georgia Institute of Technology, Emory University and PATH, a Seattle-based nonprofit organization, have teamed up to advance a technology for the painless, self-administration of flu vaccine using patches containing tiny microneedles that dissolve into the skin. Led by Pr. M. Prausnitz’s research group at Georgia Tech, the project focuses on addressing key technical issues and advancing microneedle patches through a Phase I clinical trial. Additionally, the project will be focused on comparing the effectiveness of traditional intramuscular injection of flu vaccine against administration of vaccine into the skin using microneedle patches. Finally, advanced microneedles will be developed using microfabrication technologies. This project is funded by the National Institute of Biomedical Imaging and Bioengineering (NBIB), which is part of the National Institute of Health (NIH), under the Quantum program.


 

Polymer Microneedles

 

We are working towards developing low-cost batch-fabricated single-use microneedle arrays for transdermal drug delivery. Drug delivery through micro-fabricated needles is of great interest for its capability to transport pharmaceutical and therapeutic agents, virus-like-particles, and other molecules into the body through the skin with minimal invasion and pain. Potential applications include regular immunizations (e.g., hepatitis B and measles) and annual inoculation (e.g., influenza). In this project, different types of microneedles have been successfully designed, fabricated (as shown in these images), and characterized for fluidic functionality and skin penetrability. Package, drug delivery, as well as safety are also under investigation with researchers at Georgia Tech and Emory University to reach clinical use of microfabricated needles.


Collaboration: Pr. M. Prausnitz’s research group at Georgia Tech

Sponsor: NIH

Publications
  1. J. Kim, S.-J. Paik, P.-C. Wang, S.-H. Kim, and M.G. Allen, “Maskless fabrication of high aspect ratio structures by combination of micromolding and direct drawing,” 24th IEEE International Conference on Micro Electro Mechanical Systems (MEMS2011), pp.280-283, Cancun, Mexico, Jan. 2011. (PDF)
  2. P.-C. Wang, S.-J. Paik, J. Kim, S.-H. Kim, and M.G. Allen, “Hypodermic-needle-like hollow polymer microneedle array using UV lithography into micromolds,” 24th IEEE International Conference on Micro Electro Mechanical Systems (MEMS2011), v 165, n 1, p 66-72, Jan. 2011. (PDF)
  3. S.-J. Paik, S.-H. Kim, P.-C. Wang, B. Wester, and M.G. Allen, “Dissolvable-tipped, drug-reservoir integrated microneedle array for transdermal drug delivery,” 23rd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010), pp. 312 – 315, Jan. 2010. (PDF)
  4. P.-C. Wang, B. A. Wester, S. Rajaraman, S.-J. Paik, S.-H. Kim, and M.G. Allen, “Hollow polymer microneedle array fabricated by photolithography process combined with micromolding technique,” IEEE EMBC conference, Sept. 2009. (PDF)
  5. J.-H. Park, Y.-K. Yoon, S.-O Choi, M.R. Prausnitz, and M.G. Allen, “Tapered conical polymer microneedles fabricated using an integrated lens technique for transdermal drug delivery,” IEEE Transactions on Biomedical Engineering, v 54, n 5, p 903-13, May 2007. (PDF)
  6. J.-H. Park, M.G. Allen, and M.R. Prausnitz, “Biodegradable polymer microneedles: fabrication, mechanics and transdermal drug delivery,” Journal of Controlled Release, 104:51-66, 2005. (PDF)
  • Microtweezers
  • Tactile Displays
  • Piezoelectric Actuators
  • MicroElectrode Arrays
  • Implantable Pressure Sensors
  • Microneedles
  • Solar Cells
  • Electrets
  • Force sensors
  • Micro Pulsejets
  • Conductive-Fuel Actuators
  • Gas Generators
  • Micro Power Converters
  • Magnetic Generators
  • MEMS Resonant Compass
  • Acoustic Sensors
  • Magnetic Relays
  • Inclined Nanoimprinting
  • Nanojets
  • MEMS for Nanopatterning
  • Ferroelectric RF Capacitors
  • RF Inductors
  • mm-Wave Antennas
  • HT Chemical Sensors
  • Capacitive Pressure Sensors
  • RF Flow Sensors