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Limitations with standard intradermal injections have created a clinical need for an alternative, low-cost injection device. In this study, we designed a hollow metal microneedle for reliable intradermal injection and developed a high-throughput micromolding process to produce metal microneedles with complex geometries. To fabricate the microneedles, we laser-ablated a 70 μm × 70 μm square cavity near the tip of poly(lactic acid) (PLA) microneedles. The master structure was a template for multiple micromolded poly(lactic acid-co-glycolic acid) (PLGA) replicas. Each replica was sputtered with a gold seed layer with minimal gold deposited in the cavity due to masking effects. In this way, nickel was electrodeposited selectively outside of the cavity, after which the polymer replica was dissolved to produce a hollow metal microneedle. Force-displacement tests showed the microneedles, with 12 μm thick electrodeposition, could penetrate skin with an insertion force 9 times less than their axial failure force. We injected fluid with the microneedles into pig skin in vitro and hairless guinea pig skin in vivo. The injections targeted 90 % of the material within the skin with minimal leakage onto the skin surface. We conclude that hollow microneedles made by this simple microfabrication method can achieve targeted intradermal injection.

High energy density, long cyclability, and enhanced stability in a small footprint achieved through microfabrication are crucial for micro lithium‐ion batteries. Herein, a 3D Si‐clad NiSn anode characterized by a dendritic NiSn network and silicon nanoparticles is proposed. The dendritic network facilitates fast ion/electron transfer and provides expansion space for the silicon, while the uniformly distributed silicon enhances capacity and stability. The anode, scalable to the hundred‐micron scale, is fabricated via one‐step electrodeposition incorporating the dynamic template technique. This technique generates interconnected pores extending from the inner to the outer surface of the anode, facilitating electrolyte penetration and ion transport. As a result, the anodes in the Swagelok cells exhibit an ultrahigh areal capacity of up to 28.2 mAh cm−2 and an enhanced stability of 91% capacity retention after 300 cycles. The dendritic Si‐clad NiSn anode, based on microfabrication, presents an excellent opportunity to advance micro energy systems. [ABSTRACT FROM AUTHOR]

MEMS-enabled multilayer composites, in which microfabrication is used to create micron-scale thickness layers within the volume of meso-scale thickness structures, can be exploited to create materials with highly anisotropic electromagnetic properties. Such materials have utility in both sensing and energy applications, including electrostatic and magnetic energy storage and conversion. A fabrication challenge in realizing these classes of materials lies in the size-scale disparity between the thickness of an individual layer and the desired thickness of the final anisotropic material. We demonstrate a fully additive sequential electrochemical deposition approach for such structures, which enables scalable composite volume while maintaining micron-scale individual layer thicknesses. Alternating metal and polymer layers, which exhibit very different electrical conductivities, are continuously electrodeposited in batch-scale. Individual layer thicknesses are controlled by deposition currents and times, while lateral extents are defined by lithographically defined molds. The fabrication process is illustrated using electrodeposited NiFe alloys and polypyrrole, and the anisotropy of electrical conductivity is assessed for potential use of these structures as magnetic cores for high frequency switching converters. Due to the relatively resistive polypyrrole layers, electrical anisotropy of lateral to vertical conductivity exceeding 106 was achieved. This approach offers a solution-based, microfabrication compatible, and manufacturable route to functional composite materials that exhibit high electrical anisotropies. [2020-0256] [ABSTRACT FROM AUTHOR]

This paper presents microfabricated permanent magnets possessing a multilayer structure that preserves the high magnetic energy density of thinner magnetic films, while simultaneously reducing average residual stress of the films and achieving a significant magnetic thickness. Many magnetic microelectromechanical systems (MEMS) devices heavily rely on the availability of thick (a few tens to hundreds of micrometers, high-energy-density permanent magnet components able to be deposited in a fully integrated and CMOS-compatible manner (process temperature less than 450 °C). However, it is observed that increasing magnetic film thickness typically causes a concomitant decrease in magnetic properties such as maximum energy density and increased mechanical instability (cracking and delaminating, due to the increased elastic strain energy stored in the films as magnetic volume increases), both of which limit the maximum total magnetic energy of these small-scale integrated magnets. The microlaminated permanent magnet presented here utilizes sequential multilayer electroplating in which the alternating layers of relatively thin magnetic films (CoNiP, micrometer range) and non-magnetic materials (Cu, a few tens of nanometer to micrometer range) are electrodeposited in a multilayer fashion realizing thick laminated permanent micromagnets with improved total magnetic energy as compared with their non-laminated counterparts. Low interface roughness has been demonstrated to play an important role in preserving the component magnetic thin layer properties in the multilayer configuration. [2015-0300] [ABSTRACT FROM PUBLISHER]

Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni80Fe20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300–500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g., higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc–dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W. [ABSTRACT FROM AUTHOR]

This paper presents fabrication approaches for magnesium (Mg) microstructures embedded in biodegradable polymers using through-mold Mg electrodeposition and metaltransfer-molding. Biodegradable implantable electronics have garnered increasing interest from the medical community for the monitoring and treatment of transient diseases. Magnesium is a biodegradable metal with desirable properties, and the ability to micropattern Mg thick films (i.e., about >1 μm) with direct microelectromechanical systems (MEMS) integration would support the development of more sophisticated and clinically relevant biodegradable devices and microsystems. Magnesium microstructures were electroplated through micropatterned water-soluble molds in a nonaqueous electrolyte and transfer molded into a biodegradable polymer. Electroplated Mg compared favorably with commercial Mg foil based on elemental composition, crystal orientation, electrical resistivity, and corrosion behavior. Magnesium electroplated to a thickness of up to 50 μm showed a grain size of ~10 μm, and minimum feature dimensions of 100 μm in width and spacing. Completely biodegradable Mg and poly-L-lactic acid constructs were demonstrated. The application of Mg thick films toward biodegradable energy sources was explored through the fabrication and testing of biodegradable Mg/Fe batteries. The batteries exhibited a capacity and power of up to 2.85 mAh and 39 μW, respectively. Results confirmed the advantages of electrodeposited Mg microstructures for biodegradable MEMS applications. [ABSTRACT FROM AUTHOR]

In this paper, we present the design, fabrication process, and experimental results of an electroplated metal buried interconnect and through-wafer via technology suitable for extremely low resistance interconnection of microelectronic devices. The technology is demonstrated using a 3-D daisy-chain test structure comprised of electroplated through-wafer vias buried in the silicon substrate to form the respective interconnect. In contrast to the conventional daisy-chain structures used in flip chip joining and packaging, the designed structure is fabricated on a single substrate without requiring a subsequent bonding process. The top connectors formed on the front-side of the substrate are connected to bottom connectors buried inside the substrate (buried interconnects) through 61-μm-high, void-free, fully-filled, electroplated vias. The metal electroplated buried interconnects are fabricated at the bottom surface of 232-μm-deep trenches formed on the backside of the substrate. Processes for forming deep trenches with rounded-off edges and photoresist spray coating have been developed to fabricate the buried interconnects and complete the daisy-chain structure. Developed processes enable conformal photoresist deposition inside the deep vertical trenches with excellent step and sidewall coverage, surpassing the limitations of conventional fabrication approaches. Furthermore, electroplating molds were perfectly patterned at the bottom of these deep trenches. Through-wafer vias with controllable height are fabricated by direct bottom-up plating from the buried interconnect without additional preparation, such as wafer bonding or hole filling processes. The interconnection scheme developed in this research considerably reduces the height of narrow vertical vias, compared to conventional through-wafer vias, and enables a high density array of interconnect structures. Moreover, low resistance interconnect suitable for high power applications can be realized with thick electroplated copper and fully-filled vias. Buried interconnect can be also utilized in high voltage transistor applications. Resistance testing has been performed to validate the electrical integrity of the fabricated daisy-chain structure, and the results are compared with simulation and analytical calculations. [ABSTRACT FROM AUTHOR]

We demonstrate a micromachined flexible chip-to-board chip interconnect structure for a chip scale package. Micromachined flexible interconnects enable robust operation in high thermal cycling environments, even for high pinout chips due to the flexible interconnect ability to absorb thermal expansion strain. The interconnects on the chip-side and printed wiring board (PWB)-side are united by electroplating bonding technology, a direct bonding technology resulting in solder-free, underfill-free, low temperature joining by means of copper (Cu) electroplating. Over 200 surface micromachined interconnects, which have a thermal relief geometry, are radially arranged on 1 × 1 cm2 substrates. A chip surrogate consisting of glass with integrated platinum (Pt) microheaters mimics a real electronic device under varying thermal loads. The integrated microheaters can simultaneously test mechanical and electrical performance of the interconnects by generation of on-chip temperatures up to 150°C. Lateral and vertical displacement of the interconnects in the thermal environment are measured and simulated. A mechanical reliability test of the chip scale package is successfully performed for 5000 cycles with thermal cycles of 5 min between 40 °C to 147°C. No failures were observed during this period. [ABSTRACT FROM AUTHOR]

Administration of protein and DNA biotherapeutics is limited by the need for hypodermic injection. Use of micron-scale needles to deliver drugs in a minimally invasive manner provides an attractive alternative, but application of this approach is limited by the need for suitable microneedle designs and fabrication methods. To address this need, this paper presents a conical polymer microneedle design that is fabricated using a novel integrated lens technique and analyzed for its ability to insert into the skin without mechanical failure. Microneedle master structures were fabricated using microlenses etched into a glass substrate that focused light through SU-8 negative epoxy resist to produce sharply tapered structures. Microneedle replicates were fabricated out of biodegradable polymers by micromolding. Because microneedle mechanical properties are critical to their insertion into the skin, we theoretically modeled two failure modes (axial mode and transverse mode), and analytical models were compared with measured data showing general agreement. Guided by this analysis, polymer microneedles were designed and demonstrated to insert to different depths into porcine skin in vitro. ‘Long’ polymer microneedles were also demonstrated in human subjects to insert deeply without failure. [ABSTRACT FROM AUTHOR]

Integrated inductors are typically formed either on a chip or embedded in a package or board. In this work, we explore the possibility of forming inductors in the chip-to-board interconnect layer. The solderless technique of copper (Cu) electroplating bonding is used to simultaneously form inductor structures as well as chip-to-board interconnect. The use of the gap between the chip and substrate for inductors not only increases integration density, but also allows large magnetic cross-sectional areas to be achieved. To demonstrate the technology, a plating-through-mold method has been used in the establishment of tall interconnect or solenoid inductors. For demonstration of the electroplating bonded micro solenoid structures, three and seven-turn (500 μm in height) inductors have been realized with measured inductances of 3.6 and 10.4 nH, and Q-factors of 71 and 55, respectively. As an alternative approach, a polymer-core-conductor method in which polymer posts coated with metal are electroplating bonded, has been developed. This approach reduces processing time in the fabrication of the tall metal structures. For the polymer core RF structures, three-, five-, seven-, and 10-turn inductors have been fabricated. These inductors have inductances of 4.2, 7.0, 9.6, and 13.6 nH, and Q-factors of 72, 64, 56, and 61, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the realization of a magnetic induction machine. The development of this machine is part of an ongoing project to create high-power density electric microgenerators for use in portable-power applications. The results reported here focus on testing a first-generation nonlaminated electromagnetic actuator, a metrology device designed for exploring and characterizing the fabrication process and the operating behavior of the magnetic induction micromachine. Achieving high power1 density requires large electrical currents and magnetic fluxes, which necessitate thick, multilayered microstructures that are difficult to fabricate. The batch-fabrication schemes developed as part of this work are based on low-temperature micromolding that makes extensive use of various ultra-thick photoresists and electroplatmg of electrical conductors (Cu) and ferromagnetic maternals (Ni-Fe 80%–20%), resulting m the successful fabrication of a multilayer two-phase planar stator and a planar rotor. To evaluate the performance of the complete machine (stator plus rotor), a 4-mm-diameter, 500-μm-thick electroplated Ni-Fe rotor is tethered to a series of flexible structures that prevent it from making a complete revolution, but allow accurate torque performance extraction. The tethered induction micromotor studied here exhibits torque production as high as 4.8 μN·m. [ABSTRACT FROM AUTHOR]

Explores electroplated aluminum as a material for the fabrication of microstructures, and use in the development of micromachining processes. Information on a method for the fabrication of aluminum microstructures; Demonstration of maximum structure aspect ratios.

The development and characterization of step-up transformers with high winding ratios and laminated metallic magnetic cores for MHz-range step-up transformers used in DC-DC power converters is presented. The use of metallic magnetic cores with higher saturation flux density than traditional ferrites offers the possibility of reducing the physical size of the transformers. Core eddy currents are suppressed by forming the magnetic cores in a sequential electrodeposition process through toroidal lithographic molds, followed by self-assembly. This approach results in relatively thick magnetic cores (in the hundreds of microns range), comprised of many individual laminations with micron-scale thicknesses. Transformers were formed by manual winding of primary and secondary coils on these cores. The resultant transformers, with typical dimensions in the cubic millimeter range, exhibited primary and secondary inductances in the microhenry and hundreds of microhenry ranges, respectively. Typical transformer coupling coefficients were in the range 0.85–0.95. The transformers exhibited expected voltage step-up ratios as high as 10:1 at typical operation frequencies of 1–2 MHz. These ultracompact devices exhibit up to seven times higher inductance per unit volume and five times higher inductance per weight than typical commercial coupled inductors, and show promise for use in space-constrained electronic systems. [Display omitted] • High winding ratio, ultracompact step-up transformers for DC-DC converters • Laminated cores formed in sequential electrodeposition followed by self-assembly. • Primary and secondary inductances in microhenry and hundreds of microhenry ranges • Coupling coefficient 0.85–0.95, voltage step-up ratio 10:1 at 1–2 Megahertz • Volume and weight less than commercial devices with similar inductances [ABSTRACT FROM AUTHOR]

The fabrication and characterization of vertically laminated, electrodeposited Ni-Fe magnetic cores in micromachined silicon for the low megahertz frequency range is presented. Laminated cores were fabricated by etching vertical trenches (60-180 μm wide and 525 μm deep) through silicon wafers and directly plating Ni-Fe onto the etched sidewalls. The Ni-Fe was plated over a range of thicknesses (3-53 μm) in order to study the influence of eddy currents. The measured impedances in the range 10 kHz-40 Mhz confirm the reduction of eddy current losses. This work demonstrates a simple fabrication method for achieving high-aspect-ratio, vertically laminated magnetic cores where the geometry of the structures can be easily tailored for various applications. [ABSTRACT FROM AUTHOR]

Presents information on a study which proposed a large suspended spiral-type integrated microinductor on a highly conductive silicon substrate using electroplating and surface micromachining techniques. Design and modeling; Fabrication; Experimental results and conclusion.

Abstract: This paper presents the successful design, modeling, fabrication, packaging, and characterization of a mechanically actuated micro-electro-mechanical-systems (MEMS) microtweezer. This complete and modular MEMS system has minimal manufacturing complexity and can be augmented to any standard micromanipulator or positioning system. The microtweezer is mechanically actuated and hence has minimal impact on the surrounding microenvironment, a key consideration for micromanipulation. The microtweezer components are fabricated utilizing standard electroplating based processes. The microtweezer is functionally attached to a tether-cable system packaged within a stainless steel luer needle, which can be mounted to a manual controller with a luer interface. The controller, which provides axial rotational movement of the microtweezer, can be attached to any positioning stage to allow 5+ degrees of movement freedom. Mechanical modeling and characterization of the system shows that precise and controlled tool actuation is achieved with tip closing forces averaging 360mN over an actuation range of 125μm. The system''s performance and ease of use can provide the means to create and enhance a multitude of experimental preparations previously not possible. [Copyright &y& Elsevier]

We report a scheme for the integrated fabrication of MEMS-scale, series-connected battery cells. The approach exploits multilayer electrodeposition of active and sacrificial layers to generate structures that can be formed into high voltage power sources. Aqueous, non-vacuum-based fabrication, via electrodeposition, enables high throughput and deterministic control of layer thicknesses and battery performance. Batteries manufactured using this technique offer the potential to match supply voltages to system needs, ranging from conventional electronics to direct drive of high voltage electrostatic or piezoelectric MEMS. • This paper reports a scheme for serially connected zinc-air battery stacks. • Fabrication is achieved through a sequential multilayer and stacking approach. • Scalable battery output voltages were obtained with minimal resistive loss. • Volumetric energy densities of up to 1720 WhL−1 are demonstrated. [ABSTRACT FROM AUTHOR]