Uniformity Of Arrays Research Articles

Optimization of spherically arranged lens arrays based on class II and III geodesic polyhedra

Spherical arrangement is a common way to pack lens arrays. Due to the restriction of original structures, the previous optimization methods based on icosahedral subdivision are only applicable to a few types of lens arrays adopting different numbers of sub-lenses. In order to design more types of lens arrays, an optimization packing method is proposed with the vertices of class II and class III geodesic polyhedra as the arrangement positions of sub-lenses. The vertices of the geodesic polyhedron are generated by projecting grid nodes on each face of the ortho-icosahedron to a sphere. The vertex translation function is established in a barycentric coordinate system, and then the chord ratio and packing density are used as evaluation functions to optimize the vertices’ positions. The universality of the optimization method is tested, and its robustness is certified by analyzing the optimization results of different original structures with the same number of vertices. Finally, the effectiveness and feasibility of the optimization method in engineering applications are demonstrated in a monocentric multi-scale imaging system. The optimization method proposed in this paper can significantly increase the types of lens arrays from 9 to 37 types, adopting different numbers of sub-lenses within 1000 and effectively improved the distribution uniformity of lens arrays.

Mitigation of Device Heterogeneity in Graphene Hall Sensor Arrays Using Per-Element Backgate Tuning.

Graphene Hall-effect magnetic field sensors (GHSs) exhibit high performance comparable to state-of-the-art commercial Hall sensors made from III-V semiconductors. Graphene is also amenable to CMOS-compatible fabrication processes, making GHSs attractive candidates for implementing magnetic sensor arrays for imaging fields in biosensing and scanning probe applications. However, their practical appeal is limited by response heterogeneity and drift, arising from the high sensitivity of two-dimensional (2D) materials to local device imperfections. To address this challenge, we designed a GHS array in which an individual backgate is added to each GHS, allowing the carrier density of each sensor to be electrostatically tuned independent of other sensors in the array. Compared to the constraints encountered when all devices are tuned with the same backgate, we expected that the flexibility afforded by individual tuning would allow for the array's sensitivity, uniformity, and reconfigurability to be enhanced. We fabricated an array of 16 GHSs, each with its own backgate terminal, and characterized the ability to modulate GHS carrier density and Hall sensitivity within CMOS-compatible voltage ranges. We then demonstrated that individual device tuning can be used to break the trade-off between device sensitivity and uniformity in the GHS array, allowing for enhancement of both objectives. Our results showed that GHS arrays exhibiting >30% variability under single-backgate operation could be compensated using individual tuning to achieve <2% variability with minimal impact on the array sensitivity.

Electroless deposition of nickel microbumps for fine-pith flip-chip bonding

Abstract The reliability of micro-light-emitting diode (Micro-LED) is closely associated with the uniformity of microbumps arrays. With continual decreases in pixel pitch in recent years, it is a challenge to guarantee the uniformity of bump arrays. To satisfy current requirements for ultra-high-density interconnections, this study proposes an electroless plating method for fabricating highly uniform nickel microbumps. This technique differs from electroplating, in which the morphology and consistency of microbumps can be easily controlled. Furthermore, it is a high-selectivity and cost-effective method of microbumps fabrication that eliminates solder wastage and avoids metal lift-off in traditional evaporation. To minimize the non-uniformity of the bumps, we aim to optimize the oxygen plasma treatment parameters and deposition intervals to eliminate the issues of skip plating, hydrogen bubble entrapment, and nodules. Under the combined effect of plasma treatment and intermittent deposition method, microbump arrays with less than 5% uniformity were successfully prepared, achieving the demands of high-density bonding. In addition, the preparation process is highly reproducible, extending the application range of this technique.

Enhanced fabrication of conical array via two-stage through mask electrochemical machining process

In response to the issues of low processing precision, poor surface quality, and low array uniformity in the fabrication process of metal array conical structures, this paper proposes a two-stage enhanced process for fabricating metal array conical structures using through-mask electrochemical machining (TMECM). The micro-convex structure with high consistency can be quickly obtained through the first electrochemical machining (ECM), and then the mask is removed and the micro-convex structure is modified twice. The top diameter of the micro-structure is reduced by using the phenomenon of electric field concentration in the ECM process, and the top curvature radius of the micro-structure is further reduced, so as to increase the height diameter ratio of the micro-structure and improve the surface quality. The results show that during the initial ECM, when the machining time is 35 s, the voltage is 20 volts, the flow rate of the acid etching solution is 1 m /s, the duty cycle is 50 %, and the frequency is 200 Hz, the stable machining of the metal array conical structure can be achieved. In the secondary electrochemical surface modification, it was found that under the conditions of working solution containing 2 mol/L nickel-based etching agent, pulse voltage of 20 V and processing time of 35 s, the method effectively improved the surface quality of the workpiece and ensured the stable manufacturing of the micro-conical array structure. The prepared microstructure height was 198 μm and the top diameter was 28 μm.

Microneedle-Assisted Transdermal Delivery of Lurasidone Nanoparticles.

Lurasidone, an antipsychotic medication for schizophrenia, is administered daily via oral intake. Adherence is a critical challenge, given that many schizophrenia patients deny their condition, thus making alternative delivery methods desirable. This study aimed to deliver lurasidone by the transdermal route and provide therapeutic effects for three days. Passive diffusion was found to be insufficient for lurasidone delivery. The addition of chemical enhancers increased permeation, but it was still insufficient to reach the designed target dose from a patch, so a microneedle patch array was fabricated by using biodegradable polymers. For prolonged and effective delivery, the drug was encapsulated in Poly (lactic-co-glycolic acid) (PLGA) nanoparticles which were made using the solvent evaporation method and incorporated in microneedles. Effervescent technology was also employed in the preparation of the microneedle patch to facilitate the separation of the needle tip from the patch. Once separated, only the needle tip remains embedded in the skin, thus preventing premature removal by the patient. The microneedles demonstrated robust preformation in a characterization test evaluating their insertion capacity, mechanical strength, and the uniformity of microneedle arrays, and were able to deliver a dose equivalent to 20 mg oral administration. Therefore, the potential of a transdermal delivery system for lurasidone using microneedles with nanoparticles was demonstrated.

Large‐Area Processable Ultrathin Organic Transistors with High Mobility and Mechanical Stabilities

AbstractFor applications involving the implantation of organic thin‐film transistors (OTFTs) in flexible environments, maintaining uniform device performance and ultrathin profiles with excellent mechanical stability is crucial for dynamic deformable conditions. This study presents high‐performance, mechanically flexible ultrathin OTFTs with a thickness under 5 µm, designed to be scalable for utilization in large areas. The OTFTs utilized an organosilicon polymer dielectric layer synthesized via initiated chemical vapor deposition combined with the crystalline organic semiconductor 2‐Decyl‐7‐phenyl[1]benzothieno[3,2‐b][1]benzothiophene (Ph‐BTBT‐10). Compared with conventional organic transistors, the OTFTs exhibited exceptional features, such as a charge carrier mobility of up to 7 cm2 V−1 s−1 and a near‐zero threshold voltage. Their performance is showcased across 900 devices on a 10 cm × 10 cm substrate to ensure uniformity and scalability. Additionally, the OTFTs demonstrate remarkable resilience to mechanical deformation, with a 97.4% mobility retention rate under a 20% tensile compression. After 1000 cycles of repeated deformation stress, they maintain a robust 94.6% performance level compared with the initial state. In summary, the ultrathin flexible OTFTs exhibit exceptional resilience to mechanical deformation, extended air exposure, uniformity in large arrays, and high mobility. This makes them promising for diverse applications, such as in vivo organ monitoring and skin displays.

Bioinspired labrum-shaped stereolithography (SLA) assisted 3D printed hollow microneedles (HMNs) for effectual delivery of ceftriaxone sodium

Microneedles (MNs), a microsystem having needle height in micrometers, have gained significant attention due to their minimum invasiveness, painless, and easy-to-administer nature. Here, we introduce a hollow microneedle (HMNs) array with bio-inspired labrum tip for low insertion force and desired mechanical strength, fabricated using vat-photopolymerization mediated stereolithography (SLA) assisted 3D printing technology utilizing biocompatible photo-crosslinkable and curable resin as feedstock. Fabricated HMNs was used for the effective transdermal delivery of a broad-spectrum antibiotics i.e., ceftriaxone sodium (CEF) with a high molecular weight of 554.58 g mol−1, possessing gastro-intestinal (GI) instability and low oral bioavailability (BA). The bio-inspired labrum tip structure of the fabricated HMNs was evaluated by digital microscopy and scanning electron microscopy (SEM) to ensure the printed prototype's superiority in terms of dimensions and array uniformity. The HMN microchannels were then characterized by X-ray microcomputer tomography (µCT) to ascertain the quality of internal channels and ensure even distribution of drug solution. Further, HMNs was also characterized for mechanical and penetration analysis. Suggesting a low force of 1.54 N was required for its effective penetration with a sufficient fracture force of around 171.82 N. The ex vivo skin permeation profile of CEF from the HMNs revealed 100 ± 0.80 % CEF permeation through porcine skin within 18 hr. Finally, a pre-clinical efficacy assessment of CEF-reservoir HMNs was performed in an experimental animal model, revealing efficient penetrability and desired BA of CEF. Overall results demonstrated the active transdermal drug delivery potential of these fabricated bio-inspired HMNs as a unique device for customized and personalized treatment.

One-Step Fabrication of Droplet Arrays Using a Biomimetic Structural Chip.

In the field of one-step efficient preparation of dewetting droplet arrays, the process is hampered by the requirement for low chemical wettability of solid surfaces, which restricts the complete transition of wetting state and its broad prospects in biological applications. Inspired by the physical structure of the lotus leaf, enabling it to promote the change of the infiltration state of an aqueous solution on the surface, we developed a method of one-step fabrication of droplet arrays on the biomimetic structural chip designed in the present work. This greatly reduces the need for chemical modification techniques to achieve low wettability and reduces the reliance on complex and sophisticated surface preparation techniques, thus improving the fabrication efficiency of droplet arrays fully generated on a chip by one-step operation without the need for extra liquid phase or the control of harsh barometric pressure. We also studied the influence of dimensions of the biomimetic structure and the preparation process parameters such as number of smears and speed of smearing on the preparation rate and uniformity of the droplet arrays. The amplification of templating DNA molecules in the droplet arrays prepared in a one-step fabrication way is also performed to verify its application potential for DNA molecular diagnosis.

Organic Semiconductor Single Crystal Arrays: Preparation and Applications

The study of organic semiconductor single crystal (OSSC) arrays has recently attracted considerable interest given their potential applications in flexible displays, smart wearable devices, biochemical sensors, etc. Patterning of OSSCs is the prerequisite for the realization of organic integrated circuits. Patterned OSSCs can not only decrease the crosstalk between adjacent organic field-effect transistors (OFETs), but also can be conveniently integrated with other device elements which facilitate circuits application. Tremendous efforts have been devoted in the controllable preparation of OSSC arrays, and great progress has been achieved. In this review, the general strategies for patterning OSSCs are summarized, along with the discussion of the advantages and limitations of different patterning methods. Given the identical thickness of monolayer molecular crystals (MMCs) which is beneficial to achieve super uniformity of OSSC arrays and devices, patterning of MMCs is also emphasized. Then, OFET performance is summarized with comparison of the mobility and coefficient of variation based on the OSSC arrays prepared by different methods. Furthermore, advances of OSSC array-based circuits and flexible devices of different functions are highlighted. Finally, the challenges that need to be tackled in the future are presented.

New precision electroforming process for the simultaneous improvement of thickness uniformity and microstructure homogeneity of wafer-scale nanotwinned copper arrays

Nanotwinned (nt) Cu has received much attention because of its superior mechanical and electrical properties, but only a few production processes can yield nt-Cu parts with uniform thickness and a homogeneous microstructure on the wafer scale. To solve this problem, a new precision electroforming process is proposed that combines auxiliary cathodes with pulse reverse current (PRC) electroforming, which provides a synergistic effect to increase the homogeneity of the thickness and a nanoscale twin structure. As a practical example of the proposed process, 4-inch nt-Cu lamina arrays were fabricated and numerically modeled to probe into the synergistic mechanisms. The intrinsic correlations among the array element spacing, current waveform, and main forms of thickness nonuniformity were determined. In addition, the effects of the processing parameters on the microstructural evolution and microhardness of the nt-Cu arrays were analyzed. The results indicated that such a significant improvement in thickness uniformity and microstructure homogeneity were due to the auxiliary-cathode/PRC combination, which enables maximization of the PRC leveling efficiency by inducing a uniform current distribution; this effectively ensures that the microstructures are uniform across all laminae on the wafer scale. Additionally, thick nt-Cu deposited on the current-crowding regions was preferentially stripped during the application of reverse current. This alleviates the adverse effects of the current redistribution resulting from the auxiliary cathode on the thickness uniformity of the laminae and offers additional possibilities for homogeneous growth of nt-Cu. The new precision electroforming process has significant potential to produce wafer-scale components with uniform thickness and specific microstructures.

Preparation of Oriented ZnO Rod Arrays Using Hexagonal Plate-Like Particles as a Seed Layer

ZnO rod film is a promising material for electrodes and sensors due to its large surface area and high electrical conductivity. One of the drawbacks of conventional ZnO rod film is the random orientation of rods. In this study, an oriented ZnO seed layer composed of hexagonal plate-like ZnO particles was prepared by dip-coating. An oriented ZnO rod film was then synthesized by growing this seed layer using a hydrothermal synthesis method. We optimized the concentration of the precursor and the hydrothermal treatment time to synthesize homogeneous ZnO rod arrays. The uniformity of the rod arrays was improved by applying a strong magnetic field (12 T) during hydrothermal treatment.

A 50-ps Gated VCRO-Based TDC With Compact Phase Interpolators for Flash LiDAR

This article describes a small footprint, low power gated voltage-controlled ring oscillator (VCRO)-based Time-To-Digital converter (TDC) for Flash Light Detection and Ranging (LiDAR) applications. A group of compact local phase interpolators (PIs) are used to improve the resolution, which is highly area-saving and compatible with in-pixel TDC structure. A non-reset operation mode is introduced to increase the linearity by taking advantage of the dynamic element matching (DEM) property. The proposed TDC has been fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> HV-CMOS technology in a 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times32$ </tex-math></inline-formula> array, achieving a resolution of 50 ps. A Phase Lock Loop (PLL) is adopted to track the process, voltage, and temperature (PVT) variations and make the resolution tunable. A power-saving analog buffer is used to distribute the stable control voltage to all the in-pixel TDCs. Measurements show a good linearity performance and array uniformity (a deviation of only 0.89 ps), making it suitable for Flash LiDAR applications.

Micro-diffractive optical element arrays for beam shaping

We describe the design of Fourier type array generators and beam shapers as periodic configurations of refractive-diffractive optical elements in microscale to provide specific beam shaping and imaging functionaliies. We investigate how the addition of micro-nanostructures to regular microstructure arrays enables new degrees of freedom for the design of micro-optical systems, in combination with adapted fabrication techniques yields a better optical performance and leads to enhancement of the array concept, uniformity and efficiency.

Uniformity of saturated orthogonal arrays

Orthogonal array has been used in various fields, as it possesses attractive combinatorial properties. However, for a long time, combinatorially equivalent orthogonal arrays are thought to be indistinguishable, especially when an ANOVA model is established. Later on, some papers pointed out that permuting levels of orthogonal arrays will alter their statistical inference abilities. Criteria have been recommended for evaluating the different performance of orthogonal arrays. In this paper, a revised method is proposed to construct saturated orthogonal arrays when the level of the factors is an odd prime and properties of the related wrap-around L2-discrepancy will be investigated. Theoretical result shows that the wrap-around L2-discrepancies of the saturated orthogonal arrays constructed using the revised method are less than those of the original ones, and asymptotically attain the lower bounds. A series of numerical examples also confirms the effectiveness of the proposed method.

(Invited) DNA-Directed High-Precision Assembly of High-Performance CNT FETs

Precise fabrication of semiconducting channel materials into densely-aligned uniform arrays is one prerequisite towards the high-performance ultra-scaled technology nodes, in particular for carbon nanotubes (CNTs). Traditional thin-film approaches generally yield CNTs in irregularly-spaced bundles or with wide orientation distribution, and lack a mechanism to effectively eliminate the mis-aligned CNTs from the ultra-scaled channel area. Therefore, the averaged pitch value and precision of CNT arrays, the key parameters defining lateral CNT spacing, fail to simultaneously meet all of the patterning requirements for the ultra-scaled technology nodes. Bio-fabrication is promising for patterning CNTls at a resolution beyond the existing lithographic limit. However, impacted by surface charges and sub-micron dimensions of typical bio-templates, current bio-templated electronics exhibit both poor transport performance and array uniformity smaller than 1 micron.We report precise scaling of inter-CNT pitch using a supramolecular assembly method called Spatially Hindered Integration of Nanowire Electronics (SHINE). Specifically, by using nano-trenches to align CNTs and DNA hybridization to stabilize them in place, we constructed parallel CNT arrays with uniform pitch as small as 10.4 nm, at an assembly yield over 95%. The pitch precision improves on that prepared from conventional thin-film approaches by more than two orders of magnitude. Compared to the lithography-patterned Si channels at 10 nm technology node, SHINE simultaneously provides both 70% smaller averaged pitch value and molecular-scale pitch precision in the channel area. By engineering the interfacial compositions, metal ions and surface charges that are destructive to FET performance have been excluded from the channel area without degrading CNT alignment. Under a source-to-drain voltage of -0.5 V, we demonstrate both transconductance more than 0.6 mS/μm with fast on/off switching. And the key FET performance metrics are improved by more than one order of magnitude than previous bio-templated FETs. Furthermore, we demonstrate centimeter-scale alignment of fixed-width CNT arrays. At the interface of high-performance electronics and bio-molecular self-assembly, precise bio-fabrication could provide ultra-scaled devices or circuits compatible with or sensitive to local biological environments.

Analysis of Negative Capacitance-Based Broadband Impedance Matching for CMUTs.

Tight integration of capacitive micromachined ultrasonic transducer (CMUT) arrays with integrated circuits can make active impedance matching feasible for practical imaging devices. In this article, negative capacitance-based impedance matching for CMUTs is investigated. Simple equivalent circuit model-based calculations show the potential of negative capacitance matching for improving the bandwidth along with electrical power transfer and acoustic reflectivity, but the model has limitations especially for acoustic reflectivity evaluation. For more realistic results, an experimentally validated CMUT array model is applied to a small 1-D CMUT array operating in the 5-15 MHz range. The results highlight the difference between electrical power transfer and acoustic reflectivity as well as the tradeoffs in signal-to-noise ratio (SNR). According to the results, ideal negative capacitance termination matched to the CMUT capacitance provides the broadest bandwidth and highest SNR if acoustic or electrical reflections are of no concern. On the other hand, negative capacitance and resistance matching to minimize acoustic reflectivity provides both lower reflection and closer to ideal SNR as compared with electrical power matching. It is observed that acoustic matching also reduces acoustic crosstalk and improves array uniformity. While several challenges for integrated circuit implementation are present, negative capacitance-based impedance matching can be a viable broadband active impedance matching method for CMUTs operating in conventional and collapsed mode as well as other ultrasound transducers with mainly capacitive impedance.

Growth of high-crystallinity uniform GaAs nanowire arrays by molecular beam epitaxy* *Project supported by the National Natural Science Foundation of China (Grant Nos. 61674021, 11674038, 61704011, 61904017, 11804335, and 12074045), the Developing Project of Science and Technology of Jilin Province, China (Grant No. 20200301052RQ), the Project of Education Department of Jilin Province, China (Grant No. JJKH20200763KJ), and the Youth Foundation

The self-catalyzed growth of GaAs nanowires (NWs) on silicon (Si) is an effective way to achieve integration between group III–V elements and Si. High-crystallinity uniform GaAs NW arrays were grown by solid-source molecular beam epitaxy (MBE). In this paper, we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials. The influence of natural oxidation time on the crystallinity and uniformity of GaAs NW arrays was investigated and is discussed in detail. The GaAs NW crystallinity and uniformity are maximized after 20 days of natural oxidation time. This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates. The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.

DNA-directed nanofabrication of high-performance carbon nanotube field-effect transistors.

Biofabricated semiconductor arrays exhibit smaller channel pitches than those created using existing lithographic methods. However, the metal ions within biolattices and the submicrometer dimensions of typical biotemplates result in both poor transport performance and a lack of large-area array uniformity. Using DNA-templated parallel carbon nanotube (CNT) arrays as model systems, we developed a rinsing-after-fixing approach to improve the key transport performance metrics by more than a factor of 10 compared with those of previous biotemplated field-effect transistors. We also used spatially confined placement of assembled CNT arrays within polymethyl methacrylate cavities to demonstrate centimeter-scale alignment. At the interface of high-performance electronics and biomolecular self-assembly, such approaches may enable the production of scalable biotemplated electronics that are sensitive to local biological environments.

(Invited) DNA-Directed High-Precision Assembly of CNT FETs

Precise fabrication of semiconducting channel materials into densely-aligned uniformly parallel arrays is one prerequisite to the high-performance ultra-scaled technology nodes, in particular for carbon nanotubes (CNTs). Traditional thin-film-based approaches generally yield CNTs in irregularly-spaced bundles or with wide orientation distribution, and lack a mechanism to effectively eliminate mis-aligned CNTs from the ultra-scaled channel area. Therefore, the averaged pitch value and precision of CNT arrays, the key parameters defining lateral CNT spacing, fail to simultaneously meet all of the patterning requirements for the ultra-scaled technology nodes. Bio-fabrication is promising for patterning CNTls at a resolution beyond the existing lithographic limit. However, impacted by surface charges and sub-micron dimensions of typical bio-templates, current bio-templated electronics exhibit both poor transport performance and array uniformity smaller than 1 micron.We report precise scaling of inter-CNT pitch using a supramolecular assembly method called Spatially Hindered Integration of Nanowire Electronics (SHINE). Specifically, by using nano-trenches to align CNTs and DNA hybridization to stabilize them in place, we constructed parallel CNT arrays with uniform pitch as small as 10.4 nm, at an assembly yield over 95%. The pitch precision improves on that prepared from conventional thin-film approaches by more than two orders of magnitude. Compared to the lithography-patterned Si channels at 10 nm technology node, SHINE simultaneously provides both 70% smaller averaged pitch value and molecular-scale pitch precision in the channel area. By engineering the interfacial compositions, metal ions and surface charges that are destructive to FET performance have been excluded from the channel area without degrading CNT alignment. Under a source-to-drain voltage of -0.5 V, we demonstrate both transconductance more than 0.6 mS/μm with fast on/off switching. And the key FET performance metrics are improved by more than one order of magnitude than previous bio-templated FETs. Furthermore, we demonstrate centimeter-scale alignment of fixed-width CNT arrays. At the interface of high-performance electronics and bio-molecular self-assembly, precise bio-fabrication could provide ultra-scaled devices or circuits compatible with or sensitive to local biological environments.

A photoelectrochemical biosensor based on the direct electron transfer to galactose oxidase

A novel photoelectrochemical biosensor for quantitative detection of galactose was successfully developed by immobilizing galactose oxidase on TiO2 nanorod arrays modified F-doped tin oxide (FTO) electrode. Specifically, the direct electron transfer to galactose oxidase was achieved. TiO2 nanorod arrays directly grew on FTO electrode from peroxotitanium complex precursor under low-temperature and normal-pressure conditions. The large surface area and good uniformity of TiO2 nanorod arrays facilitated direct electron transfer between the electrode surface and galactose oxidase. The photocurrent spectra of as-prepared biosensor showed an obvious photocurrent response under UV light irradiation. The generated photocurrent of the stable platform was significantly enhanced after the addition of galactose in solution and the photocurrent intensity possessed linear relationship with the galactose concentration. Moreover, CaCl2, uric acid and ascorbic acid had no interference with the detection of galactose on the working electrode. This sensor can be reused and measure the concentration of galactose in lactose-free milk.