On-chip Micro Research Articles

On-Chip Thermoelectric Devices Based on Standard Silicon Processing.

The strong reduction of thermal conductivity with respect to bulk silicon makes nanostructured silicon one of the best materials for highly efficient direct conversion of heat into electrical power and vice-versa. The widespread technologies for the integration of silicon devices can be used to define on-chip micro thermoelectric generators (scavengers); similar structures could also be used for precise and well-localized cooling through the reverse process of heat pumping. However, the road to the fabrication of integrated thermal energy scavengers or cooler, based on silicon, is still very long. In this work, the design and the fabrication process of on-chip thermoelectric devices based on a large number of interconnected monocrystalline silicon nanobeams, very tall (>1 µm) and thin (less than 200 nanometers), arranged in large areas combs is shown. The small width of the nanobeams gives a reduced thermal conductivity, and the height perpendicular to the substrate allows the definition of a highly dense collection of nanostructures. The total cross-sectionis far broader than that of other nanostructures, a characteristic that guarantees both mechanical stability and larger deliverable power per unit area.

On-Chip Micro Temperature Controllers Based on Freestanding Thermoelectric Nano Films for Low-Power Electronics

HighlightsDense and flat freestanding Bi2Te3-based thermoelectric nano films were successfully fabricated by sputtering technology using a newly developed nano graphene oxide membrane as a substrate.On-chip micro temperature controllers were integrated using conventional micro-electromechanical system technology, to achieve energy-efficient temperature control for low-power electronics.The tunable equivalent thermal resistance enables an ultrahigh temperature control capability of 100 K mW−1 and an ultra-fast cooling rate exceeding 2000 K s−1, as well as excellent reliability of up to 1 million cycles.

Sputtered LiFePO4 for Solid State Batteries

The progress in microelectronics and micro/nanoelectromechanical technologies allows for miniaturization and optimization of the electronic devices used in our daily life. To assure the energy supply to such devices, this progress should be accompanied by the development of micro power generators able fulfil the energy demand when being integrated on the microchips.The working principle of that kind of micro storage systems, namely, micro batteries, would not be different from the existing ones. By means of an electrochemical reaction, the chemical energy stored in the electrodes of the battery is converted to electrical energy. Lithium-ion batteries (LIBs) are the state-of-the-art configuration that allow for the best compromise between the amount of energy stored, and the power at which this energy can be delivered. When referring to lithium-ion micro batteries, the working principle is not different from the traditional one. However, there are some main differences. The first is that organic liquid electrolytes could hardly be included, due to their leakage risk. Moreover, these electrolytes are flammable and could constitute a safety issue when included in microdevices. Additionally, the miniaturization of the battery device involves thin layer deposition for all the battery components [1]. In this regards, physical deposition techniques (sputtering, atomic layer deposition, etc.) have been demonstrated to be promising techniques for on-chip micro batteries fabrication [2,3].LiFePO4 thin film layers have been attracting some attention due to their compromise between cost, performance, and availability.In this study, LiFePO4 thin film cathodes have been obtained on a platinum coated silicon wafer by sputtering, which allows to deposit a well-controlled thickness and composition. Due to LiFePO4 ‘s acceptable electrical conductivity, it was possible to carry out the deposition both in direct current and radiofrequency mode. Both processes have been used with the aim of understanding if any difference arises in the deposited film because of the sputtering method. The LiFePO4 film was characterized by means of Atomic Force Microscope (AFM) to measure the thickness of the deposited layer, X-Ray Diffraction (XRD) to investigate the crystalline phases present, Scanning Electron Microscopy (SEM) to analyse the morphology and the homogeneity of the composition and Raman spectroscopy to assess the chemical and physical structure. Finally, the deposition condition as well as the post-treatments were correlated to the electrochemical behaviour of the LiFePO4-coated Pt-Si wafer by cyclic voltammetry, demonstrating the feasibility of the as-obtained LiFePO4 for the application as positive electrode in on-chip Li-ion micro batteries.

Efficient Design for Integrated Photonic Waveguides with Agile Dispersion.

Chromatic dispersion engineering of photonic waveguide is of great importance for Photonic Integrated Circuit in broad applications, including on-chip CD compensation, supercontinuum generation, Kerr-comb generation, micro resonator and mode-locked laser. Linear propagation behavior and nonlinear effects of the light wave can be manipulated by engineering CD, in order to manipulate the temporal shape and frequency spectrum. Therefore, agile shapes of dispersion profiles, including typically wideband flat dispersion, are highly desired among various applications. In this study, we demonstrate a novel method for agile dispersion engineering of integrated photonic waveguide. Based on a horizontal double-slot structure, we obtained agile dispersion shapes, including broadband low dispersion, constant dispersion and slope-maintained linear dispersion. The proposed inverse design method is objectively-motivated and automation-supported. Dispersion in the range of 0–1.5 ps/(nm·km) for 861-nm bandwidth has been achieved, which shows superior performance for broadband low dispersion. Numerical simulation of the Kerr frequency comb was carried out utilizing the obtained dispersion shapes and a comb spectrum for 1068-nm bandwidth with a 20-dB power variation was generated. Significant potential for integrated photonic design automation can be expected.

On-chip micro pressure sensor for microfluidic pressure monitoring

In this work, a novel on-chip micro pressure sensor was developed for microfluidic pressure monitoring. Polydimethylsiloxane (PDMS) microfluidic chip contained a working fluid channel with a sealed detection channel beneath it. Any change in pressure in the working fluid channel would change the volume of the detection channel. A mixture of two immiscible fluids was sealed in the detection channel. The pressure of the working fluid can be monitored by measuring the interface displacement of the two fluids in the detection channel. A PDMS film between the working channel and detection channel can avoid cross-contamination between fluids. We acquired a calibration curve of the pressure sensor for measurement and optimized the performance of the sensor through parametric studies. Moreover, two pressure sensors were integrated into a microchip to characterize the pressure drop in the microchannel. The developed pressure sensor is inexpensive and easy to be integrated into microfluidic devices to monitor the flow conditions for cell culture, fluid mixing, and droplet manipulation.

On-Chip High-Power Supply Unit: Micro Supercapacitor With Superb Capacitance Density and Fast Charge/Discharge Ability

Stable working voltage is critical for integrated systems to keep functioning, yet it suffered from instantaneous high-power demands and the resulting voltage disturbance. An on-chip micro supercapacitor (MSC) with superb capacitance density can act as a promising high-power supply unit to satisfy power demands and stabilize the system. However, severe capacitance decay of MSC under fast charge/discharge rate greatly weakens the device power output thus making it incompetent. This work demonstrates an on-chip high-power MSC featured by the improved capacitance density, fast charge/discharge ability and scaling-down capability. The improvement is brought by the applied mesoporous gold as electrode framework, which offers fast electronic/ionic pathway and reduces porous effect under high charge/discharge rate; as well as the uniform MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> active layer, which is decorated by an electrochemical potential-modulated deposition method, providing large pseudocapacitance. Moreover, the asymmetric electrode structure is constructed to expand the single device operation voltage. As a result, a large steady capacitance density of 9 mF/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and small capacity loss of 28% at high scan rate of 1 V/s have been achieved, leading to an unprecedented power density of 138 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

On-Chip Micro Mixer Driven by Elastic Wall with Virtual Actuator

In this paper, we propose an on-chip micromixer driven by an elastic wall with a virtual actuator. The on-chip micro mixer is composed of a circular chamber surrounded by a ring-shaped channel under isolation with an elastic wall. When vibrational pressure is put on the driving channel by an actuator, the volume of the circular chamber changes through the deformation of the elastic wall, as if there exists a virtual actuator near the wall. As a result, the liquid in the circular chamber is pushed out and pulled through the neck channel. This action creates a swirling flow in the circular chamber while maintaining isolation from the driving channel. Through experiments, we confirmed the swirling flow under an isolated environment using an air-based valve. The advantage of this approach is that the micromixer can be designed with a single layer having a simple mechanism.

Serially Arranged Wall Driving On-Chip Micro Mixer

Serially Arranged Wall Driving On-Chip Micro Mixer

Design and fabrication of an on-chip micro flow cytometer with integrated micro-lens

In this paper, the design and fabrication of an on-chip micro flow cytometer chip with integrated micro-lens with a size of 1500 mm × 1000 mm × 2 mm is put forward, and the chip mainly consists of the unit of three-dimensional micro fluidic channel used for hydraulic focusing and the unit of micro-lens used for optical detection. In specific, firstly, the technology of the tilted ultra-violet (UV) lithography and the secondary overlay UV lithography of SU-8 resist are used to build a mould. Then, soft photolithography of polydimethylsiloxane (PDMS) is utilized to make a PDMS double casting to get a chip structure consistent with the original mould. Finally, after bonding, this PDMS chip, being injected with fluid with a certain pressure, can be changed into the micro flow cytometer with integrated micro-lens in situ on the same chip. The experiment shows that because the shape of the micro-lens in the chip can be changed with the change of the pressure and the amount of the liquid injected, the chip can meet the practical needs. Moreover, this kind of chips shares the merits of small size, simple fabrication process, low cost, and mass production as well.

Cascaded second-order optical nonlinearities in on-chip micro rings.

We demonstrate cascaded Stimulated Raman Scattering (SRS), Second-Harmonic Generation (SHG), and Sum-Frequency Generation (SFG) in integrated on-chip whispering-gallery resonators (WGRs). These lithium niobate-based WGRs are fabricated using highly-parallel semiconductor manufacturing techniques coupled with specialized polishing as a post-processing step and thus represent a novel means for batch fabrication of this family of non-linear devices. We achieved record high Q-factors for on-chip lithium niobate WGRs reaching up to 3 × 106. Furthermore, we present a flexible but stable coupling scheme, which gives us the opportunity to optimize the coupling regarding the non-linear optical processes we observe.

On-chip electrochromic micro display for a disposable bio-sensor chip

This paper reports an on-chip electrochromic micro display made of polyaniline (PANi) which can be easily made on a CMOS chip. Micro-patterned PANi thin films were selectively deposited on pre-patterned microelectrodes by using electrodeposition. The optimum conditions for deposition and electrochromism were investigated. An 8-pixel on-chip micro display was made on a Si chip. The color of each PANi film could be independently but simultaneously controlled, which means any 1-byte digital data could be displayed on the display. The PANi display had a response time as fast as about 100 ms, which means the transfer data rate was as fast as 80 bits per second.

A Review of On-Chip Micro Supercapacitors for Integrated Self-Powering Systems

Miniaturized self-powering systems that integrate both energy harvesters and energy storage units as the power sources are essential to realize maintenance-free wireless sensor networks, implantable medical devices, and active radio frequency identification systems. On-chip micro supercapacitors (MSCs) are promising candidates for energy storage in such systems by providing high power densities, fast charge/discharge rates, and long cycle life. Researchers have been improving the performances, especially energy and power densities, of MSCs in recent years. This paper reviews the fundamental working mechanisms and design considerations of on-chip MSCs with special emphasis on the advantages of 3-D configurations. Typical fabrication methods are summarized, and their effects on the device performance and system integration are analyzed. In particular, the power generation of micro energy harvesters and the power consumption of typical wireless micro systems are surveyed, providing the basic and targeting performance requirements of future MSCs that can be integrated with them. [2017-0069]

Enabling tunable micromechanical bandpass filters through phase-change materials

Vanadium dioxide (VO2), one of the most promising phase-change smart materials, has shown strong frequency tuning capabilities in MEMS resonators. In this paper, we demonstrate the potential use of VO2-based MEMS devices as second-order kilohertz (kHz) bandpass filters with tunable band selectivity and adjustable bandwidth (BW). Two identical on-chip micro resonators are actuated using mechanical excitation and measured using optical detection. One of the resonators is not actuated while the other is tuned by applying electric currents across an integrated resistive heater, which induces the phase transition of the VO2, and consequently a large stress to the mechanical structure. The responses of both MEMS resonators are combined, resulting in a resonant peak of tunable BW controlled by the input current. The BW can be extended to 2.62 times by using two bridges or 2.39 times by implementing one pair of cantilevers. The results for both devices are discussed.

Amorphous Silicon-Doped Titania Films for on-Chip Photonics

High quality optical thin film materials form a basis for on-chip photonic micro- and nanodevices, where several photonic elements form an optical circuit. Their realization generally requires the thin film to have a higher refractive index than the substrate material. Here, we demonstrate a method of depositing amorphous TiO2 films doped with 25% Si on various substrates, a way of shaping these films into photonic elements, such as optical waveguides and resonators, and finally, the performance of these elements. The quality of the film is estimated by measuring thin film cavity Q-factors in excess of 105 at a wavelength of 790 nm, corresponding to low propagation losses of 5.1 db/cm. With a refractive index of n > 2, the film supports waveguiding on different substrates, such as quartz, YAG, and sapphire, and shows evanescent coupling to chromium ions embedded in YAG, presenting film–substrate interaction. Additional functionalization of the films by doping with optically active rare-earth ions such as ...

141 反応性イオンエッチングにより作製したオンチップマイクロクヌーセンポンプ

141 反応性イオンエッチングにより作製したオンチップマイクロクヌーセンポンプ

Printable on-chip micro battery for disposal bio-sensing device

This paper reports an on-chip micro battery which can be fabricated on a CMOS chip. The battery consists of screen-printed Mg and AgCl films. An open circuit voltage of 1.58 V, the maximum power of 1.4 mW and a total stored energy of 400 mJ were obtained from anode and cathode electrodes of about 3 × 3 mm2. Demonstration devices self-powered by the on-chip battery worked in a 0.14 M NaCl solution, and digital data transmission from the devices using optical and electrical field methods were confirmed.

Electronic desalting for controlling the ionic environment in droplet-based biosensing platforms.

The ability to control the ionic environment in saline waters and aqueous electrolytes is useful for desalination as well as electronic biosensing. We demonstrate a method of electronic desalting at micro-scale through on-chip micro electrodes. We show that, while desalting is limited in bulk solutions with unlimited availability of salts, significant desalting of ≥1 mM solutions can be achieved in sub-nanoliter volume droplets with diameters of ∼250 μm. Within these droplets, by using platinum-black microelectrodes and electrochemical surface treatments, we can enhance the electrode surface area to achieve >99% and 41% salt removal in 1 mM and 10 mM salt concentrations, respectively. Through self-consistent simulations and experimental measurements, we demonstrate that conventional double-layer theory over-predicts the desalting capacity and, hence, cannot be used to model systems that are mass limited or undergoing significant salt removal from the bulk. Our results will provide a better understanding of capacitive desalination, as well as a method for salt manipulation in high-throughput droplet-based microfluidic sensing platforms.

Experimental and Theoretical Evaluation of On-Chip Micro Heat Pipe

The performance of a specially fabricated micro heat pipe etched on a silicon wafer is analyzed to evaluate its cooling potential. Triangular microgrooves are etched on a silicon wafer via a lithographic process with two reservoirs at the two ends. Anodic bonding and electrochemical spark erosion techniques are used to seal the microgrooves with a thin Pyrex glass and to create holes for vacuum connections and coolant insertion, respectively. The cooling potential of the micro heat pipe is evaluated by accurately measuring the temperature distributions along the channel length at different values of the applied heat load. A mathematical model is proposed and numerically solved to evaluate the axial variation of the radius of curvature of the coolant film to examine the cooling potential of the on-chip micro heat pipe system.

A Low-Power and Low-Voltage Power Management Strategy for On-Chip Micro Solar Cells

Fundamental characteristics of on-chip micro solar cell (MSC) structures were investigated in this study. Several MSC structures using different layers in three different CMOS processes were designed and fabricated. Effects of PN junction structure and process technology on solar cell performance were measured. Parameters for low-power and low-voltage implementation of power management strategy and boost converter based circuits utilizing fractional voltage maximum power point tracking (FVMPPT) algorithm were determined. The FVMPPT algorithm works based on the fraction between the maximum power point operation voltage and the open circuit voltage of the solar cell structure. This ratio is typically between 0.72 and 0.78 for commercially available poly crystalline silicon solar cells that produce several watts of power under typical daylight illumination. Measurements showed that the fractional voltage ratio is much higher and fairly constant between 0.82 and 0.85 for on-chip mono crystalline silicon micro solar cell structures that produce micro watts of power. Mono crystalline silicon solar cell structures were observed to result in better power fill factor (PFF) that is higher than 74% indicating a higher energy harvesting efficiency.

30pm1-A-6 使い捨てバイオセンサチップのためのオンチップバッテリの開発

This paper reports an on-chip micro battery for a disposal bio-sensor chip, which has simple structure made of Mg and AgCl films and can be easily fabricated on a CMOS chip. The battery is activated by adding NaCl into an inspection solution. The open circuit voltage of 1.6 V, and the maximum power of 1.8 mW could be generated by the on-chip battery with 3 x 3 mm^2 electrodes. Macro models using a commercially available LSI and the developed on-chip battery were developed and evaluated. The LSI could be successfully operated by the on-chip battery and the digital data could be transferred by optical and electrical methods.