Silicon Micro Research Articles

Retraction Note: Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Retraction Note: Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Vertical Interconnection Technology for RF MicroSystem Packaging.

In this work, 1.5-level interconnections of RF microsystems with good RF performance, integration process compatibility, and high reliability are developed to meet the future demand for wireless communication microsystems in the millimeter wave band. Numerical models of 1.5-level interconnections based on solder balls with different diameters are established and analyzed using HFSS. The optimized structure parameters of 0.2 mm diameter Sn96.5Ag3Cu0.5 (SAC305) solder balls and 0.3 mm diameter Sn63Pb37 solder balls are selected for the interconnection between glass micro substrates and silicon micro substrates and between silicon micro substrates and HTCC substrates, respectively. Integration process parameters of the vertical interconnection are optimized. The micro substrate interconnection samples manufactured based on optimized integration methods and parameters show high reliability.

Micromachined needle-like calorimetric flow sensor for sap flux density measurement in the xylem of plants

Miniaturized silicon thermal probes for plant’s sap flow measurement, or micro sap flow sensors, have advantages in minimum invasiveness, low power consumption, and fast responses. Practical applications in sap flow measurement has been demonstrated with the single-probe silicon micro sensors. However, the sensors could not detect flow directions and require estimating zero sap flow output that leads to significant source of uncertainty. Furthermore, silicon-needles would break easily during the insertion into plants. We present the first three-element micro thermal sap flow sensor packaged on a durable printed circuit board needle that can measure bidirectional flows with improved dynamics and precision. The performance of the newly designed calorimetric flow sensor was confirmed through precision calibration and field test on tomato stems. A calibration curve for a tomato stem was obtained with a sensitivity of 0.299 K/(µL mm−2 s−1) under the maximum temperature increase of 4.61 K. Results from the field test for one month revealed a correlation between the measured sap flux density and related conditions such as solar radiation, vapor pressure deficit, sunshade and irrigation. The developed sensor will contribute to practical long-term sap flow monitoring for small and delicate plants with minimal physical invasion.

Voltage- and Metal-assisted Chemical Etching of Micro and Nano Structures in Silicon: A Comprehensive Review.

Sculpting silicon at the micro and nano scales has been game-changing to mold bulk silicon properties and expand, in turn, applications of silicon beyond electronics, namely, in photonics, sensing, medicine, and mechanics, to cite a few. Voltage- and metal-assisted chemical etching (ECE and MaCE, respectively) of silicon in acidic electrolytes have emerged over other micro and nanostructuring technologies thanks to their unique etching features. ECE and MaCE have enabled the fabrication of novel structures and devices not achievable otherwise, complementing those feasible with the deep reactive ion etching (DRIE) technology, the gold standard in silicon machining. Here, a comprehensive review of ECE and MaCE for silicon micro and nanomachining is provided. The chemistry and physics ruling the dissolution of silicon are dissected and similarities and differences between ECE and MaCE are discussed showing thattheyare the two sides of the same coin. The processes governing the anisotropic etching of designed silicon micro and nanostructures are analyzed, and the modulation of etching profile over depthis discussed. The preparation of micro- and nanostructures with tailored optical, mechanical, and thermo(electrical) properties is then addressed, and their applications in photonics, (bio)sensing, (nano)medicine, and micromechanical systems are surveyed. Eventually, ECE and MaCE are benchmarked against DRIE, and future perspectives are highlighted.

Fabrication of efficient and economical dye-sensitized solar cells using carbon-coated nanotextured silicon wafers counter electrodes

Significant progress has been made in various fields of photovoltaics in response to the growing demand for alternative energy resources. Silicon technologies dominate the current solar cell market, but carbon-based photovoltaics are known for their ability to be produced at low cost and in large quantities. The electrocatalyst accelerates the conversion of tri-iodide into iodide ions at the interface between the counter electrode and the electrolyte, according to DSSC principle. During the catalytic process, the accessible sites for the reaction between the reactants and the catalyst are greatly influenced by the surface area and morphology of the counter electrode and electrocatalyst. Therefore, in this work, silicon micro cubes with different patterns were fabricated using lithography, and a carbon layer has been coated directly using chemical vapor deposition on the surface of silicon samples with 15, 30, and 60 mins growth times. The functionalized silicon surface with the carbon layer subsequently demonstrated electrocatalytic activities for iodide/triiodide reduction. In DSSCs, the carbon-coated samples have been utilized as counter electrodes. The samples were characterized using Raman spectroscopy and scanning electron microscopy. DSSCs were fabricated for each synthesized counter electrode, and DSSCs performance has been analyzed for each DSSC. Utilizing carbon-coated nanotextured silicon wafers as the counter electrodes, DSSCs were able to achieve the maximum power conversion efficiency of 6.73%. The current results pave the way toward the replacement of expensive Pt-based conventional DSSCs.

Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Multistage Micropump System towards Vacuum Pressure

Fraunhofer EMFT’s research and manufacturing portfolio includes piezoelectrically actuated silicon micro diaphragm pumps with passive flap valves. Research and development in the field of microfluidics have been dedicated for many years to the use of micropumps for generating positive and negative pressures, as well as delivering various media. However, for some applications, only small amounts of fluid need to be pumped, compressed, or evacuated, and until now, only macroscopic pumps with high power consumption have been able to achieve the necessary flow rate and pressure, especially for compressible media such as air. To address these requirements, one potential approach is to use a multistage of high-performing micropumps optimized to negative pressure. In this paper, we present several possible ways to cascade piezoelectric silicon micropumps with passive flap valves to achieve these stringent requirements. Initially, simulations are conducted to generate negative pressures with different cascading methods. The first multistage option assumes pressure equalization over the piezo-actuator by the upstream pump, while for the second case, the actuator diaphragm operates against atmospheric pressure. Subsequently, measurement results for the generation of negative gas pressures down to −82.1 kPa relative to atmospheric pressure (19.2 kPa absolute) with a multistage of three micropumps are presented. This research enables further miniaturization of many applications with high-performance requirements for micropumps, achievable with these multistage systems.

Ultrathin Crystalline Silicon Nano and Micro Membranes with High Areal Density for Low-Cost Flexible Electronics.

Ultrathin crystalline silicon is widely used as an active material for high-performance, flexible, and stretchable electronics, from simple passive and active components to complex integrated circuits, due to its excellent electrical and mechanical properties. However, in contrast to conventional silicon wafer-based devices, ultrathin crystalline silicon-based electronics require an expensive and rather complicated fabrication process. Although silicon-on-insulator (SOI) wafers are commonly used to obtain a single layer of crystalline silicon, they are costly and difficult to process. Therefore, as an alternative to SOI wafers-based thin layers, here, a simple transfer method is proposed for printing ultrathin multiple crystalline silicon sheets with thicknesses between 300nm to 13µm and high areal density (>90%) from a single mother wafer. Theoretically, the silicon nano/micro membrane can be generated until the mother wafer is completely consumed. In addition, the electronic applications of silicon membranes are successfully demonstrated through the fabrication of a flexible solar cell and flexible NMOS transistor arrays.

Feasibility for early cancer diagnostics by machine learning enabled synchrotron radiation based micro X-ray fluorescence imaging of trace biometals as cancer biomarkers

Trace quantitative spectroscopic imaging has the potential to provide the location and distribution of trace biometals in a biological sample for disease (cancer) diagnostics. However, spatial qualitative analysis of the trace biometals for cancer diagnostics remains a challenge due to the complex biological matrices that result in weak analyte signals and intricate multivariate relationships between the analyte spatial distribution and disease (cancer) state. In this study, principal component analysis (PCA)-enabled artificial neural networks (ANN) for micro X-ray fluorescence for simultaneous determination of biometal (Mn, Fe, Cu and Se) spatial profiles as biomarkers for cancer diagnosis in model human cell cultures (DU145 and Vero). The cell lines were cultured on silicon nitride membranes and micro XRF analysis carried out at TwinMic beamline, Elletra synchrotron source at beam excitation energy of 1.7 keV. These enabled 2D mapping of Mn, Fe, Cu and Se using cylindrical beam dimensions of Æ690 nm in stepper motor-controlled step sizes of 0.6μm with dwell times of 10s per pixel. Python multichannel analyzer (PyMca) software was used for spectral deconvolution and determination of 2D maps of the trace biometals. Principal component analysis (PCA) reduced the data dimensions for optimal artificial neural networks (ANN) exploratory modelling of cancer pathogenesis stages utilizing the pixel spectral profile of the trace biometals (Mn, Fe, Cu, Se). The 2D spatial distribution maps of the trace biometals revealed high spatial correlations between Cu and Fe ((0.941) and (0.923)) in DU_D3 and DU_D4 in cancerous compared to normal cell culture stages (V_D3 and V_D4) at 0.661 and 0.203 respectively. Utilizing PC1 and PC2 scores from selected fluorescence L (Lα and Lβ) lines of Fe and Cu, ANN distinctively classified the cell cultures into cancerous and healthy groups. Further, the selected fluorescence L-lines of Fe, Cu and Compton scatter spectral profiles enabled ANN classification of cancerous cultured cells into early, intermediate and advanced stages. The study has provided proof of concept for early diagnosis of cancer based on the multivariate alterations and spatial distribution of the trace biometals as cancer biomarkers.

Design of analog front-end readout circuit for capacitive silicon micro gyroscope

To design a high-performance analog front-end readout circuit for capacitive silicon micromachined gyroscope, this paper presents electrical modeling of the silicon micromachined gyroscope according to its working characteristics, proposes to construct the amplitude and frequency range of the silicon micromachined gyroscope signal in the form of a capacitor array, and designs the capacitance readout circuit of the gyroscope based on this model. Based on the SMIC 0.18 um CMOS process, the electrical model and its capacitance readout circuit are designed and simulated in this paper. The results indicate that the capacitance readout circuit can accurately detect the equivalent variable capacitance signal of the gyroscope electrical model and transform it linearly into a voltage signal. The equivalent output noise of the overall analog front-end readout circuit is 80.11 nV/√Hz@6.4kHZ. The system resolution can reach 0.29 aF. As a result, the silicon micro gyroscope analog front-end circuit has a wide range of capacitive applications, high linearity, low noise, and broad market and application prospects. Hence, this topic is of great scientific significance.

Facile Process for Fabrication of Silicon Micro-Nanostructures of Different Shapes as Molds for Fabricating Flexible Micro-Nanostructures and Wearable Sensors.

We report a method to fabricate silicon micro-nanostructures of different shapes by tuning the number of layers and the sizes of self-assembled polystyrene beads, which serve as the mask, and by tuning the reactive ion etching (RIE) time. This process is simple, scalable, and inexpensive without using any sophisticated nanomanufacturing equipment. Specifically, in this work, we demonstrate the proposed process by fabricating silicon micro- or nanoflowers, micro- or nanobells, nanopyramids, and nanotriangles using a self-assembled monolayer or bilayer of polystyrene beads as the mask. We also fabricate flexible micro-nanostructures by using silicon molds with micro-nanostructures. Finally, we demonstrate the fabrication of bandage-type electrochemical sensors with micro-nanostructured working electrodes for detecting dopamine, a neurotransmitter related to stress and neurodegenerative diseases in artificial sweat. All these demonstrations indicate that the proposed process provides a low-cost, easy-to-use approach for fabricating silicon micro-nanostructures and flexible micro-nanostructures, thus paving a way for developing wearable micro-nanostructures enabled sensors for a variety of applications in an efficient manner.

Adsorption of chloramphenicol from water using Carex meyeriana Kunth-derived hierarchical porous carbon with open channel arrays.

A carbon material with both open macrochannel arrays and abundant micro/mesopores was prepared, characterized, and applied for removing chloramphenicol (CAP) from water. In the preparation process, Carex meyeriana Kunth (CM) with natural channel arrays was used as the precursor for producing the biochar, and NaOH was used for removing silicon and formatting micro- and mesopores of the porous carbon. The product (PCCM) exhibited the highest specific surface area (2700.24 m2g-1) among the reported CM-derived porous carbons. The adsorption performances of PCCM were evaluated through batch adsorption experiments. The maximum adsorption capacity of PCCM toward CAP was 1659.43mgg-1. The adsorption mechanism was investigated with the aid of theoretical calculations. Moreover, PCCM exhibited better performance than other porous carbon adsorbents in fixed-bed experiments, which may be due to its structural advantages.

Preparation of silicone oil nanoemulsion softeners using different surfactants and their effect on physical characteristics of polyester fabric

AbstractSilicone oil nanoemulsion softeners with different particle sizes can be prepared using different surfactants with various ratios aminosilicone oil, surfactants concentration and time of mixing. The silicone oil nanoemulsion softeners could penetrate well into the polyester fibers; therefore, they can induce desirable physicochemical properties in the fabric. In current study, we first prepared silicone oil nanoemulsion softeners by designing via DOE software and with different particle sizes using nonyl phenol, octyl phenyl ether and fatty alcohol surfactants, and we investigated them using dynamic light scattering (DLS) and transmission electron microscope (TEM) techniques. In DOE software, the effect of various independent variables of emulsification process such as surfactant type, oil weight fraction, surfactant concentration and time of mixing on dependent variables were studied including particle size, z‐average and width. Then, we examined the physical characteristics of polyester fabric by applying silicone oil macro, micro and nanoemulsion softeners. The treated fabrics with these softeners were compared with each other through the physical properties. The scanning electron microscopy (SEM) analysis showed the polyester fabric treated with silicone nanoemulsion softeners appeared to have smoother fiber surface. To prove the penetration of silicone particles into the fabric fibers, a cross section was taken from the cross section of polyester fabric by microtome in liquid nitrogen. The TEM images from cross section of fabrics treated with the silicone oil nanoemulsion softeners confirmed that the nanoparticles had penetrated well into the polyester fibers; therefore, they could induce desirable physicochemical properties in the fabric.

Formulation design of a new type of epoxy resin-based insulating adhesive and research on its high temperature resistance

A series of new epoxy resin adhesives were prepared by low viscosity bisphenol A epoxy resin E-44 and E-51as the matrix, low molecular polyamide 650# and phenolic modified JT-3008 as the curing agent, silicon micro powder and calcium carbonate as the fillers. The gelation time, surface drying time and shear strength of the samples were deeply tested. The thermal decomposition temperature and high temperature resistance of the samples were determined by TG analysis. Meanwhile, the surface fracture morphology was observed by SEM. The results showed that a new kind of heat epoxy resin insulation adhesive with long gelation time and convenient construction and meeting the requirements of production adjustment was successfully obtained through the optimization design of the formula,. The new epoxy resin insulation adhesive showed excellent mechanical properties with 18.00 MPa shear strength, which can be used at 380 ℃ for a short period of time and 130 ℃ for a long time. The new adhesive developed in this paper can be widely used in high voltage switchgear and other insulation materials, which has good application prospects.

Formulation design of a new type of epoxy resin-based insulating adhesive and research on its high temperature resistance

A series of new epoxy resin adhesives were prepared by low viscosity bisphenol A epoxy resin E-44 and E-51as the matrix, low molecular polyamide 650# and phenolic modified JT-3008 as the curing agent, silicon micro powder and calcium carbonate as the fillers. The gelation time, surface drying time and shear strength of the samples were deeply tested. The thermal decomposition temperature and high temperature resistance of the samples were determined by TG analysis. Meanwhile, the surface fracture morphology was observed by SEM. The results showed that a new kind of heat epoxy resin insulation adhesive with long gelation time and convenient construction and meeting the requirements of production adjustment was successfully obtained through the optimization design of the formula,. The new epoxy resin insulation adhesive showed excellent mechanical properties with 18.00 MPa shear strength, which can be used at 380 ℃ for a short period of time and 130 ℃ for a long time. The new adhesive developed in this paper can be widely used in high voltage switchgear and other insulation materials, which has good application prospects.

Vapor-Phase Chemical Etching of Silicon Assisted by Graphene Oxide for Microfabrication and Microcontact Printing

Chemical etching of silicon assisted by a number of catalysts is attracting increasing attention in the fabrication of silicon micro–nanostructures. In practical applications, metal-free catalysts, including carbon materials, have been focused on as alternative materials for the assisted etching of silicon. Although this anisotropic etching process is suitable for the fabrication of silicon micro–nanostructures due to its simplicity and cost effectiveness, a number of challenges remain, such as the formation of a porous layer and peeling of the catalyst by the gases produced during the etching process. We herein report vapor-phase etching assisted by graphene oxide and its mechanism in terms of reaction kinetics. By optimizing etching conditions, graphene oxide enhances the etching reaction in the vapor phase without the formation of a porous layer. We also demonstrated the formation of micrometer-sized pores in the desired areas by combining the microcontact printing of graphene oxide with silicon etching in the vapor phase.

Optical Sensing of Chlorophyll(in) With Dual-Spectrum Si LEDs in SOI-CMOS Technology

Small and low-cost chlorophyll sensors are popular in agricultural sector and food-quality control.Combining such sensors with silicon CMOS electronics is challenged by the absence of silicon-integrated light-sources.We experimentally achieve optical absorption sensing of chlorophyll based pigments with silicon (Si) micro light-emitting diodes (LED) as light-source, fabricated in a standard SOI-CMOS technology.By driving a Si LED in both forward and avalanche modes of operation,we steer its electroluminescentspectrum between visible (400–900 nm) and near-infrared (~1120 nm). For detection of chlorophyll in solution phase, the dualspectrum light from the LED propagates vertically through glycerol micro-droplets containing sodium copper chlorophyllin at varying relative concentrations. The transmitted light is detected via an off-chip Si photodiode. The visible to near-infrared color ratio (COR) of the photocurrent yields the effective absorption coefficient. We introduce the LED-specificmolar absorption coefficient as ametric to compute the absolute pigment concentration (~0.019 ± 0.006 mol L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ) and validate the results by measurements with a hybrid spectrophotometer. With the same sensor, we also show noninvasive monitoring of chlorophyll in plant leaves. COR sensitivities <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 3.9 \times 10^{4}$ </tex-math></inline-formula> mol <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> L and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5.3 \times 10^{4}$ </tex-math></inline-formula> mol <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> L are obtained for two leaf species, where light from the LED propagates diffusely through the thickness of the leaf prior to detection by the photodiode. Our work demonstrates the feasibility of realizing fully CMOS-integrated optical sensors for biochemical analyses in food sector and plant/human health.

Dislocation-Induced Energy Dissipation in a Tunable Trilayer Graphene Resonator

In crystalline materials, the creation and modulation of dislocations are often associated with plastic deformation and energy dissipation. Here we report a study on the energy dissipation of a trilayer graphene ribbon resonator. The vibration of the ribbon generates cyclic mechanical loading to the graphene ribbon, during which mechanical energy is dissipated as heat. Measuring the quality factor of the graphene resonator provides a way to evaluate the energy dissipation. The graphene ribbon is integrated with silicon micro actuators, allowing its in-plane tension to be finely tuned. As we gradually increased the tension, we observed, in addition to the well-known resonance frequency increase, a large change in the energy dissipation. We propose that the dominating energy dissipation mechanism shifts over three regions. With small applied tension, the graphene is in elastic region, and the major energy dissipation is through graphene edge folding; as the tension increases, dislocations start to develop in the sample to gradually dominate the energy dissipation; finally, at large enough tension, graphene layers become decoupled and start to slide and cause friction, which induces the more severe energy dissipation. The generation and modulation of dislocations are modeled by molecular dynamics calculation and a method to count the energy loss is proposed and compared to the experiment.

A Photochemical Microfluidic Reactor for Photosensitized [2+2] Cycloadditions

AbstractHere we report a microfluidic system for photochemical cycloadditions fabricated using silicon micro processing technologies. The system was optimized to yield residence times of just a few minutes for a range of photochemical [2+2]-cycloaddition reactions facilitated using high power UV-LEDs at 375 nm and triplet photosensitizers, which removed the need for the low wavelengths typically required for these types of transformations. Adducts using different excitable olefins with different linear, carbocyclic, and heterocyclic coupling partners were explored to demonstrate the feasibility of performing photochemistry in microflow in an academic research environment. Finally, a reaction leading to a novel dihydrooxepin-2(3H)-one scaffold and a mechanistic proposal for its formation are reported.

Modelling, Simulation and Analysis of NPDA for Sub-retinal implant using Nano Materials

There are two primary illnesses that afflict the elderly worldwide those are Retinitis Pigmentosa (RP) and Age-related Macula Degeneration (AMD). Presently there has been a large research focus to develop treatment methods that would cure AMD induced vision disability and RP diseases. Silicon Micro Photo Diode Array, ARGUS II, and ALPHA IMS are a few of the latest therapeutic approaches suggested for curing these diseases (MPDA). These systems have led to many undesirable side effects in patients. The objective of this research work is to create an affordable device that improves the vision recovery. Photovoltaic cells composed of nanomaterials such as carbon nanotubes and graphene are known as Nano Photo Diode Arrays (NPDA). Under incident light, they may generate stimulating electrical pulses to restore vision, photoreceptor cells are stimulated in the retina. The authors of this study sought to optimise the several geometries of Graphene/SWCNT-C60/Al bilayer hetero junction photodiodes that would constitute the NPDA for subretinal implantation.