Three-dimensional Microcoils Research Articles

Design and simulation of a micro-coiled digitally-controlled variable inductor with a monolithically integrated MEMS switch

This work introduces the design, analysis, simulation, and a standard MEMS fabrication process for a three-dimensional micro-coil with a magnetic core and a digital switch configuration using a completely integrated, fully MEMS-compatible process to achieve a digitally controlled inductance. The proposed design can also be utilized as a micro-transformer. The proposed design consists of five identical 3D coils and their corresponding MEMS switches. These coils are digitally controlled to achieve a variable inductor ranging from one-fifth of the coil inductance up to five times the coil inductance. A standard five-layer Polymumps process is proposed to fabricate the micro-coils and the integrated switches. Each micro coil is anchored directly on-chip, which is connected to the input signal from one side, and the other is connected to the switch. The Ni-based magnetic core improves the coil’s response by confining and guiding the magnetic field in the magnetic device compared to Si core based by more than five times. The presented coil has the number of windings limited by the designed length and the minimum spacing that can be realized by standard optical lithography. The coil’s diameter is also restricted by the limits defined by optical lithography, whereas the maximum height realizable by the Polymumps process limits the height of the magnetic core and accordingly results in lower inductor performance. Based on this technique, we present coils ranging from 100 μm length and ten winding up to 1000 μm length and 100 windings. The new monolithically integrated MEMS switches act as selectors to achieve a variable inductance with digital control to allow the selection among n(n + 1)/2 inductance steps, where n is the number of coils.

Stretchable conductors based on three-dimensional microcoils for tunable radio-frequency antennas

3D deformable metallic microcoils were aligned and nano-welded to fabricate stretchable conductors for flexible tunable antennas.

Performance enhancement of the synchronous micropump based on experimental and numerical investigations of the magnetic field flux density in planar microcoils

This study presents numerical and experimental investigations targeting enhancing the magnetic field flux magnitudes in electroplated copper microcoils. Improved designs are used in the development of a new generation of the electromagnetic-based synchronous micropump in order to enhance its performance (i.e. the maximum achievable output pressure and flow rate). The synchronous micropump concept is based on managing the movement of two magnets in an annular fluidic channel. The magnets’ rotation is achieved by sequentially activating a set of three-dimensional microcoils to repel or attract one magnet (travelling piston) through the channel, whereas the second one is anchored between the inlet and the outlet ports (valve piston). At the end of each pumping cycle, the magnets exchange their functions. To achieve the maximum achievable output pressure and flow rate, higher magnetic fields without exceeding the material temperature limitation are required. The stronger the magnetic fields that can be generated, the higher the hydraulic power that the pump can deliver. The microcoil conductor width and height were optimized to generate higher magnetic field flux intensity within the pump limitation parameters (i.e. pump footprint and coils’ maximum heat dissipation limit). The new generation of the synchronous pump was run at a rotational speed of up to 800 rpm and provided a maximum flow rate of 3.56 ml/min and a maximum pressure head of 687 Pa.

High-level integration of three-dimensional microcoils array in fused silica.

Rapid and facile creation of three-dimensional (3D) microcoils array in a "lab-on-a-chip" platform is a big challenge in micromachining. Here we report a method based on an improved femtosecond-laser wet-etch (FLWE) technology and metal-microsolidifying process for the fabrication of 3D microcoils array inside fused silica. Based on this approach, we fabricated microcoil arrays such as 3×3 O-shaped microcoils array and 4×4 liner microcoils array. By injecting high-melting-point alloy, the electrocircuit of microcoils array can hardly be disconnected. The microcoils array also exhibits good uniformity and a high integration level. It shows promise as a real application device.

Process for the fabrication of complex three-dimensional microcoils in fused silica

The creation of complex three-dimensional (3D) microcoils has attracted significant attention from both scientific and applied research communities. However, it still remains challenging to build 3D microcoils with arbitrary configurations using conventional planar lithographic fabrication methods. This Letter presents a new facile method based on an improved femtosecond laser wet etch technology and metal microsolidifying process for the fabrication of on-chip complex 3D microcoils inside fused silica. The diameter of the microcoils is about 30 μm, and the effective length of the microchannel is about 13 mm. The aspect ratio of the microcoils can be larger than 400:1, and the microchannel exhibiting good uniformity and smoothness also has good flowability for high-viscosity conductive gallium metal. Based on this approach, we fabricated complex microcoils such as U-shaped and O-shaped microcoils that can be easily integrated into a "lab on a chip" platform or microelectric system inside fused-silica substrate.

Facile fabrication of true three-dimensional microcoils inside fused silica by a femtosecond laser

This paper presents a facile method for the fabrication of on-chip three-dimensional (3D) microcoils inside fused silica. The main fabrication process involves two steps: (1) creating 3D helical microchannels inside fused silica using an improved femtosecond laser irradiation assisted by chemical etching (FLICE) technology and (2) conductive treatment by injecting metal gallium into the helical microchannels. The high aspect ratio 3D helical microcoil was prepared inside fused silica with a diameter of 100 µm, a length of 880 µm and a pitch of coil of 44 µm. The method is flexible to fabricate microcoils inside fused silica with arbitrary geometry configurations and different coil properties. This type of microcoils can be easily integrated into ‘lab on a chip’ (LOC) platform inside fused silica substrate.

Three-Dimensional Micro-Coil Oscillator Fabricated with Monolithic Process on LSI

Integration technique of three-dimensional micro coils on high-performance RF-LSI is one of the key technologies to realize future wireless telecommunication services and hypersensitive capacitance sensor systems. We design and fabricate monolithic three-dimensional micro coils on LSI substrate. The micro-coil has long legs, which will minimize electromagnetic coupling to the LSI substrate. We succeed in confirming the basic operation of the integrated oscillator circuit in GHz frequency range. It is conformed that process damages by plasma ashing, heating at 200 degrees Celsius, and sputter etching process are not observed in the oscillation performance.

Three-dimensional microcoils as terahertz metamaterial with electric and magnetic response

A metamaterial consisting of three-dimensional submillimeter solenoidal coils is presented. The structures have been fabricated by an automated wire-bonding technique and are characterized by terahertz time-domain spectroscopy and numerical simulations. We demonstrate the excitation of electric and magnetic resonances in the microcoils at frequencies between 0.05 and 0.6 THz. The implementation of these microstructures provides a promising route for the design of nonplanar and intrinsically chiral metamaterials for gigahertz to terahertz frequencies.

편재형 컴퓨팅을 위한 미세구조 에너지 하베스팅 시스템의 구조 설계

In this paper, we designed micro-structured electromagnetic transducers for energy harvesting and verified the performance of proposed transducers using finite element analysis software, COMSOL Multiphysics. To achieve higher energy transduce efficiency, around the magnetic core material, three-dimensional micro-coil structures with high number of turns are fabricated using semiconductor fabrication process technologies. To find relations between device size and energy transduce efficiency, generated electrical power values of seven different sizes of transducers (, , , , , , and ) are analyzed on various magnetic flux density environment ranging from 0.84 T to 1.54 T and it showed that size of device can generate at the 8 Hz of environmental kinetic energy. Compare to other electromagnetic energy harvesters, proposed system showed competitive performance in terms of power generation, operation bandwidth and size. Since proposed system can generate electric power at very low frequency of kinetic energy from typical life environment including walking and body movement, it is expected that proposed system can be effectively applied to various pervasive computing applications including power source of embodied medical equipment, power source of RFID sensors and etc. as an secondary power sources.

Two- and three-dimensional microcoil fabrication process for three-axis magnetic sensors on flexible substrates

This work presents a fabrication process validation for planar and 3D microcoils (microsolenoids) as three-axis magnetic sensors. The devices are elaborated on flexible substrates (Kapton ® and Peek ®) to allow its location as close as possible to the surface to be characterized. The fabrication process is based on copper micromoulding. For planar microcoils, the process implements only one step of micromoulding: photolithography of a 18 μm thick photoresist and copper growth by electrodeposition through the patterned photoresist. Matrices of 1–80 turns planar microcoils with an external size of less than 2 mm, a thickness of 5–15 μm, a width of 5–20 μm and 5–10 μm track spacing have been realized. For microsolenoids, the process, more original, implements only two steps of micromoulding. The second one uses a 3D photolithography process of a 18 μm thick photoresist and a copper electrodeposition with an overflow technique. The fabricated microsolenoids are comprised of 10 or 13 wires whose sizes are 30 μm in length, 18 μm in height and 8 or 10 μm in width and spacing. The electrical tests show high values of inductance for planar devices (up to 1 μH) and values of about 1 nH for microsolenoids. For both types of devices the Q-factors are about 20.

Fabrication of planar and three-dimensional microcoils on flexible substrates

Inductors are basic components of magnetic sensors. Generally, with those sensors, a weak magnetic variation has to be detected. As the sensitivity increases with the inductance value, our objectives are to design inductors with a maximum of turns while keeping millimetric sizes for the sensor. In this work, we present two microcoil fabrication processes compatible with rigid and flexible substrates. The first one is used for the realization of planar microcoils with one step of copper micromoulding. For example, a 40-turn microcoil of 1 mm external diameter and 5 μm copper width and spacing wires has been obtained. The second process allows the fabrication of three-dimensional microcoils (microsolenoids). It is based on two steps of copper micromoulding. In this process, a grey-tone photolithography step is implemented. Microsolenoids with 10–13 wires have been realized.