On-chip Process Research Articles

Immunity Enhancement of the Power Distribution Network in Integrated Circuits With Coplanar Meander Lines in Package

Integrated circuits suffer from interference in frequency multibands in real scenarios, and this susceptibility allows them to easily malfunction. In this article, a novel miniature coplanar filter in package to enhance the immunity of integrated circuits is proposed. The coplanar structure of the filter can avoid cost issues of the multilayers and can also be implemented in the substrate or interposer of the package, and also in a flexible/foldable board, with normal board, fabrication process. Analysis of the filtering characteristics and design method of a miniature filter with the required stop bands are demonstrated in detail. The designed band-stop filter can deteriorate noises in the required frequency bands, thus enhancing the immunity of integrated circuits. The immunity enhancement is validated with standard direct power injection measurements for the designed chip with or without our designed filter in package. The proposed methodology could be useful as a design guide to improve the immunity of integrated circuits without costly on-chip area and process.

Rapid Fabrication of Protein Microarrays via Autogeneration and on-Chip Purification of Biotinylated Probes.

A streamlined approach toward the rapid fabrication of streptavidin-biotin-based protein microarrays was investigated. First, using our engineered versatile plasmid (pBADcM-tBirA) and an optimal coexpression strategy for biotin ligase and biotin acceptor peptide (BAP) chimeric recombinant protein, an autogeneration system for biotinylated probes was developed. This system permitted an advantageous biotinylation of BAP chimeric recombinant proteins, providing a strategy for the high-throughput synthesis of biotinylated probes. Then, to bypass the conventional rate-limiting steps, we employed an on-chip purification process to immobilize the biotinylated probes with high-throughput recombinant lysates. The integration of the autogeneration of probes and on-chip purification not only contributed to the effective and reliable fabrication of the protein microarray, but also enabled simplification of the process and an automated throughput format. This labor- and cost-effective approach may facilitate the use of protein microarrays for diagnosis, pharmacology, proteomics, and other laboratory initiatives.

An on-Chip Planar Broadband 3-Way Power Divider for Josephson Voltage Circuits

This article presents a superconducting material based planar broadband 3-way Wilkinson power divider which can be used in the Josephson quantum voltage device for the voltage standards. The 3-way Wilkinson power divider aims to improve the integration of Josephson voltage device compared to the commonly used 2-way power divider. A two-stage λ /4 section on each branch is used to increase the bandwidth, and a π model with lumped equivalent elements are used to further decrease physical dimension in device area. Different from the conventional spatial design of N-way Wilkinson power divider, this work designs a planar broadband 3-way divider to be compatible with the on-chip fabrication process. Simulation results show that the insert loss is below 0.18 dB at working bandwidth of 16.7∼23 GHz, the division imbalance of each branch is below 0.044 dB, and the input and output reflection is better than 15 and 11.9 dB, respectively. The isolation between any of the three output ports is better than 11.8 dB. All these indexes satisfy the requirement of the Josephson voltage standard application. To further prove the validity of our design, real device based on superconducting material is realized and characterized. Devices with a 3-way power divider and three 2-stacked Josephson junction arrays with 256 junctions in each array are fabricated. The experiment results indicate the potential usage of our design in quantum voltage standard devices for high-voltage output.

Enrichment of Semiconducting Single-Walled Carbon Nanotubes with Indigo-Fluorene-Based Copolymers and Their Use in Printed Thin-Film Transistors and Carbon Dioxide Gas Sensors.

High-purity semiconducting single-walled carbon nanotubes (sc-SWCNTs) are promising for portable and high-sensitivity gas sensors because of their excellent physical and electrical properties. Here, we describe the synthesis of a novel indigo-fluorene-based copolymer (PFIDBoc) that has been designed to selectively enrich sc-SWCNTs with excellent purity (>99.9%) yet contain a latent function in the form of a tert-butoxy (t-BOC)-protected amine that can be later revealed and exploited for carbon dioxide (CO2) gas sensing. SWCNTs wrapped with the PFIDBoc polymer can be easily converted via an on-chip thermal process to reveal a vinylogous amide moiety with a secondary amine nitrogen within the indigo building block of the copolymer which is perfectly suited for CO2 recognition. Thin-film transistors and sensors were inkjet-printed onto rigid and flexible substrates, demonstrating the versatility of enriched PFIDBoc-derived sc-SWCNT dispersions. The printed transistors exhibited a mobility up to 9 cm2 V-1 s-1 and on/off current ratios >105. We further demonstrate herein a CO2 sensor for indoor air quality monitoring even in low humidity environments, possessing a linear response with up to ∼5.4% sensitivity and a dynamic range between 400 and 2000 ppm in air with a relative humidity of ∼ 40%.

Hardware-Efficient VLSI Design for Cascade Support Vector Machine with On-Chip Training and Classification Capability

Local processing of machine learning algorithms like support vector machine (SVM) is preferred over the cloud for many real-time embedded applications. However, such embedded systems often have stringent energy constraints besides throughput and accuracy requirements. Hence, hardware-efficient design to compute SVM is critical to enable these applications. In this paper, a hardware-efficient SVM learning unit is proposed using reduced number of multiplications and approximate computing techniques. These design techniques helped the learning unit to achieve 46.97% and 35.72% reductions in area and power when compared with those of the design using full multipliers. The proposed SVM learning unit supports on-chip training and classification. Energy-efficient dual-core, quad-core and octa-core cascade SVM systems were developed using the proposed SVM learning unit to expedite the on-chip training process. The runtime and energy efficiency of the cascade SVM systems improved with an increase in the number of cores. Interestingly, an average speedup of 421x in training time and a remarkable energy reduction of 24,497x were observed for the octa-core cascade SVM system when compared with the software SVM solution running on Intel Core i5-5257U processor. Moreover, the proposed octa-core cascade SVM system showed 73.75% and 65.78% lower area and power, respectively, than those of state-of-the-art cascade SVM architecture.

Multi-Level Analysis of On-Chip Optical Wireless Links

Networks-on-chip are being regarded as a promising solution to meet the on-going requirement for higher and higher computation capacity. In view of future kilo-cores architectures, electrical wired connections are likely to become inefficient and alternative technologies are being widely investigated. Wireless communications on chip may be therefore leveraged to overcome the bottleneck of physical interconnections. This work deals with wireless networks-on-chip at optical frequencies, which can simplify the network layout and reduce the communication latency, easing the antenna on-chip integration process at the same time. On the other end, optical wireless communication on-chip can be limited by the heavy propagation losses and the possible cross-link interference. Assessment of the optical wireless network in terms of bit error probability and maximum communication range is here investigated through a multi-level approach. Manifold aspects, concurring to the final system performance, are simultaneously taken into account, like the antenna radiation properties, the data-rate of the core-to core communication, the geometrical and electromagnetic layout of the chip and the noise and interference level. Simulations results suggest that communication up to some hundreds of μm can be pursued provided that the antenna design and/or the target data-rate are carefully tailored to the actual layout of the chip.

Simultaneous detection of two growth factors from human single-embryo culture medium by a bead-based digital microfluidic chip

The measurement of growth factors released in a culture medium is considered to be an attractive non-invasive approach, apart from the embryo morphology, to identify the condition of an embryo development after fertilization in vitro (IVF), but the available embryo culture medium in the current method is only a few microlitres. This small sample volume, also of small concentration, makes difficult the application of a conventional detection method, such as an enzyme-linked immunosorbent assay (ELISA). A reliable detection of the growth factor from each embryo culture medium of such a small concentration hence remains a challenge. Here for the first time we report the results of measurement of not just one, but two, growth factors, human IL-1β and human TNF-α, from an individual droplet of embryo culture medium with a bead-based digital microfluidic chip. The required sample volume for a single measurement is only 520 nL; the total duration of the on-chip process is less than 40 min. Using the culture media of human embryos with normal morphologic features, we found that the concentrations of TNF-α change little from day 3 to day 5–6, but the concentrations of IL-1β for some embryos might double from day 3 to day 5–6. For other embryos even with similar normal morphologic features, some growth factors, such as IL-1β, might exhibit different expressions during the culture period. Those growth factors could serve to distinguish the development conditions of each embryo, not merely from an observation of embryo morphology.

Investigation of off-chip and on-chip self-assembly of amphiphilic diblock copolymers based on poly(dimethylsiloxane) and poly(oligo(ethylene glycol)methacrylate)

This study aims to optimize the molecular architecture of poly(dimethylsiloxane)-b-poly(oligo (ethylene glycol) methacrylate) (PDMS-b-POEGMA) amphiphilic copolymers and investigate the phase behavior in solutions via alteration of chemical composition, initial concentrations of copolymers, none-solvent entry rates in the dialysis method, and also alterations in the micelle preparation methodology. To this end, PDMS-b-POEGMA copolymers are synthesized with different compositions and sequence lengths. Careful monitoring of the morphological permutations of polymeric nanoparticles in aqueous solution is performed through the dialysis method as an off-chip approach. Spherical and rod morphologies with different sizes are acquired due to variations in the properties of copolymer solutions such as chemical composition, concentration and the rate of water as non-solvent. For the on-chip process, a suitable microfluidic reactor is designed via a Shrinky-Dink method to produce micelles and compare them with micelles prepared by the dialysis method. Applying the on-chip method decreases the particle size from 500 to 50 nm, and reduces the particle size distribution from about 0.8 to 0.4. Hence, the particles reached from the microfluidic technique are smaller with a narrower particle size distribution, compared to those obtained from the off-chip method.

Directionally controlled open channel microfluidics

Free-surface microscale flows have been attracting increasing attention from the research community in recent times, as attributable to their diverse fields of applications ranging from fluid mixing and particle manipulation to biochemical processing on a chip. Traditionally, electrically driven processes governing free surface microfluidics are mostly effective in manipulating fluids having characteristically low values of the electrical conductivity (lower than 0.085 S/m). Biological and biochemical processes, on the other hand, typically aim to manipulate fluids having higher electrical conductivities (>0.1 S/m). To circumvent the inherent limitation of traditional electrokinetic processes in manipulating highly conductive fluids in free surface flows, here we experimentally develop a novel on-chip methodology for the same by exploiting the interaction between an alternating electric current and an induced thermal field. We show that the consequent local gradients in physical properties as well as interfacial tension can be tuned to direct the flow toward a specific location on the interface. The present experimental design opens up a new realm of on-chip process control without necessitating the creation of a geometric confinement. We envisage that this will also open up research avenues on open-channel microfluidics, an area that has vastly remained unexplored.

Spatiotemporally Controlled Multiplexed Photothermal Microfluidic Pumping under Monitoring of On-Chip Thermal Imaging.

Intelligent contactless microfluidic pumping strategies have been increasingly desirable for operation of lab-on-a-chip devices. Herein, we present a photothermal microfluidic pumping strategy for on-chip multiplexed cargo transport in a contactless and spatiotemporally controllable fashion based on the application of near-infrared laser-driven photothermal effect in microfluidic paper-based devices (μPDs). Graphene oxide (GO)-doped thermoresponsive poly(N-isopropylacrylamide)-acrylamide hydrogels served as the photothermally responsive cargo reservoirs on the μPDs. In response to remote contactless irradiation by an 808 nm laser, on-chip phase transition of the composite hydrogels was actuated in a switchlike manner as a result of the photothermal effect of GO, enabling robust on-chip pumping of cargoes from the hydrogels to predefined arrays of reaction zones. The thermal imaging technique was employed to monitor the on-chip photothermal pumping process. The microfluidic pumping performance can be spatiotemporally controlled in a quantitative way by remotely tuning the laser power, irradiation time, and GO concentration. The pumping strategy was exemplified by FeCl3 and horseradish peroxidase as the model cargoes to implement on-chip Prussian blue- and 3,3',5,5'-tetramethylbenzidine-based colorimetric reactions, respectively. Furthermore, multiplexed on-demand microfluidic pumping was achieved by flexibly adjusting the irradiation pathway and the microfluidic pattern. The new microfluidic pumping strategy shows great promise for diverse microfluidic applications due to its flexibility, high integratability into lab-on-a-chip devices, and contactless and spatiotemporal controllability.

Latency, Throughput and Power Aware Adaptive NoC Routing on Orthogonal Convex Faulty Region

Reliability of a Network-on-Chip (NoC) relies vastly upon the efficiency of handling faults. Faults those lead to trouble during on-chip communication process are basically of two types namely soft and hard. Here, hard faults are considered. Hard faults may be caused due to failure of links, routers, or other processing units. These are mainly dealt with fault-tolerant routing algorithms or by employing redundant hardware. Multiple faulty nodes are being avoided by acquiring region-based approaches. Most of the fault-tolerant routing techniques are designed on homogeneous faulty regions where some active nodes also act as deactivated nodes to build the region homogeneous. On the other hand, adaptive routing on nonhomogeneous faulty regions increases load on its boundary and most of them does not assure deadlock freeness. This paper proposes a deadlock-free adaptive fault-tolerant NoC routing named F-Route-NoC-Mesh (FRNM) ignoring any virtual channel on orthogonal convex faulty regions. Contributions of this work focus on balancing network traffic by assuming a virtual faulty block boundary and routing packets through this virtual boundary. Destination does not exist within that virtual faulty block regions to reduce load on the boundary of orthogonal faulty regions. Thus, this work is aimed at acquiring proper incorporation of procedures being able to reach fault-tolerant degree, routing efficiency and performance enhancement. Using the proposed algorithm (FRNM), a fault block model-based approach is developed. Significant improvements of average latency (43.37% to 60.44%), average throughput (4.18% to 90.81%) and power consumption (5.93% to 33.28%) are achieved over the state-of-the-art by using a cycle accurate simulator.

Interactions between photons and excitons in micro-nano photonic structures

The strong localized field in micro-nano photonic structures brings new opportunities for the study of the light-matter interaction. By designing optical modes in these structures, photons and excitons in micro-nanostructures can exchange energy reversibly or irreversibly. In this paper, a series of our recent studies on the strong and weak photon-emitter coupling in micro-nano structures especially in plasmonic and their coupled structures are reviewed, such as the principle of efficient, tunable and directional single photon emission, and engineering the electromagnetic vacuum for enhancing the coupling between photon and exciton. These results provide new physical contents for the light-matter interactions on micro and nanoscale, and have potential applications in the on-chip quantum information process and the construction of scalable quantum networks.

Joule heating-induced particle manipulation on a microfluidic chip.

We develop an electrokinetic technique that continuously manipulates colloidal particles to concentrate into patterned particulate groups in an energy efficient way, by exclusive harnessing of the intrinsic Joule heating effects. Our technique exploits the alternating current electrothermal flow phenomenon which is generated due to the interaction between non-uniform electric and thermal fields. Highly non-uniform electric field generates sharp temperature gradients by generating spatially-varying Joule heat that varies along the radial direction from a concentrated point hotspot. Sharp temperature gradients induce a local variation in electric properties which, in turn, generate a strong electrothermal vortex. The imposed fluid flow brings the colloidal particles at the centre of the hotspot and enables particle aggregation. Furthermore, maneuvering structures of the Joule heating spots, different patterns of particle clustering may be formed in a low power budget, thus opening up a new realm of on-chip particle manipulation process without necessitating a highly focused laser beam which is much complicated and demands higher power budget. This technique can find its use in Lab-on-a-chip devices to manipulate particle groups, including biological cells.

LIBRA: Thermal and Process Variation Aware Reliability Management in Photonic Networks-on-Chip

Silicon nanophotonics technology is being considered for future networks-on-chip (NoCs) as it can enable high bandwidth density and lower latency with traversal of data at the speed of light. But, the operation of photonic NoCs (PNoCs) is very sensitive to on-chip temperature and process variations. These variations can create significant reliability issues for PNoCs. For example, a microring resonator (MR) may resonate at another wavelength instead of its designated wavelength due to thermal and/or process variations, which can lead to bandwidth wastage and data corruption in PNoCs. This paper proposes a novel run-time framework called LIBRA to overcome temperature- and process variation- induced reliability issues in PNoCs. The framework consists of (i) a device-level reactive MR assignment mechanism that dynamically assigns a group of MRs to reliably modulate/receive data in a waveguide based on the chip thermal and process variation characteristics; and (ii) a system-level proactive thread migration technique to avoid on-chip thermal threshold violations and reduce MR tuning/ trimming power by dynamically migrating threads between cores. Our simulation results indicate that LIBRA can reliably satisfy on-chip thermal thresholds and maintain high network bandwidth while reducing total power by up to 61.3 percent, and thermal tuning/trimming power by up to 76.2 percent over state-of-the-art thermal and process variation aware solutions.

On-Chip Growth of SnO2/ZnO Core–Shell Nanosheet Arrays for Ethanol Detection

In this letter, well-defined SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /ZnO core-shell nanosheet arrays (NSAs) are grown with an on-chip two-step process as gas sensing materials. A homogeneous precipitation method has been used to synthesize SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NSAs, following by atomic layer deposition of ZnO. The SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /ZnO core-shell NSAs based sensor exhibits significantly enhanced ethanol sensing response (13.3 at 100 ppm) and selectivity at 350 °C, as compared with the pure SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NSAs (2.7 at 100 ppm). The improvement of sensor performance can be ascribed to the SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /ZnO heterostructures formed in the core-shell NSAs, which suggests the promising application for MEMS compatible ethanol sensors.

Modeling, simulation, and employing dilution-dialysis microfluidic chip (DDMC) for heightening proteins refolding efficiency.

Miniaturized systems based on the principles of microfluidics are widely used in various fields, such as biochemical and biomedical applications. Systematic design processes are demanded the proper use of these microfluidic devices based on mathematical simulations. Aggregated proteins (e.g., inclusion bodies) in solution with chaotropic agents (such as urea) at high concentration in combination with reducing agents are denatured. Refolding methods to achieve the native proteins from inclusion bodies of recombinant protein relying on denaturant dilution or dialysis approaches for suppressing protein aggregation is very important in the industrial field. In this paper, a modeling approach is introduced and employed that enables a compact and cost-effective method for on-chip refolding process. The innovative aspect of the presented refolding method is incorporation dialysis and dilution. Dilution-dialysis microfluidic chip (DDMC) increases productivity folding of proteins with the gradual reduction of the amount of urea. It has shown the potential of DDMC for performing refolding of protein trials. The principles of the microfluidic device detailed in this paper are to produce protein on the dilution with slow mixing through diffusion of a denatured protein solution and stepwise dialysis of a refolding buffer flowing together and the flow regime is creeping flow. The operation of DDMC was modeled in two dimensions. This system simulated by COMSOL Multiphysics Modeling Software. The simulation results for a microfluidic refolding chip showed that DDMC was deemed to be perfectly suitable for control decreasing urea in the fluid model. The DDMC was validated through an experimental study. According to the results, refolding efficiency of denaturant Hen egg white lysozyme (HEWL) (EC 3.2.1.17) used as a model protein was improved. Regard to the remaining activity test, it was increased from 42.6 in simple dilution to 93.7 using DDMC.

On-Chip Fabrication of a Cell-Derived Extracellular Matrix Sheet.

The extracellular matrix (ECM) provides physical and chemical support to the surrounding cells. During cell growth, ECM secretion and network formation influence cell morphology, cell adhesion, cell-to-cell interactions, and cell migration. Microfluidics-based cell culture systems are limited by the integration of structural ECM into the device. We report the development of a cell-derived ECM-incorporated microfluidic device that can provide structural characteristics and biochemical components of cell-derived ECM. Using an on-chip decellularization process, we constructed an ECM sheet, secreted and deposited from monolayer-cultured mouse embryonic fibroblasts (NIH/3T3), inside the microfluidic device. ECM components (including collagens, fibronectin, laminin, and elastin) and mesh-type fibronectin fibrous architecture were maintained on the surface of the porous membrane of the microfluidic device after decellularization. To verify the usability of the fibroblast-derived ECM sheet integrated microfluidic device in a cell culture platform, we tested the recellularization of human umbilical vein endothelial cells (HUVEC) and analyzed HUVEC-ECM and HUVEC-HUVEC interactions. On the ECM sheet, HUVECs exhibited morphologies and focal adhesion features that were markedly different from those of other groups. We then explored the effect of the ECM sheet on HUVEC mechanosensitivity. An increase in fluid shear stresses led to focal adhesion and the polymerization and reorganization of HUVEC adherens junctions, similar to natural junctional development, whereas the control group exhibited stimuli-insensitive behaviors. We conclude that the decellularized ECM sheet-incorporated microfluidic device provides an in vivo-like physical and biochemical ECM microenvironment for microfluidics-based cell culture.

A high-efficiency micromixing effect by pulsed AC electrothermal flow

PurposeThe on-chip high-throughput mixing process is one of the main challenges in the preparation process in clinical diagnostics. Because of high laminar flow in micro-channel, the fluid should be disturbed by external force. This paper aims to study pulsed AC electrothermal flow and the multiphysic interaction between the fluid behavior, external electric field, temperature field and convection-diffusion field to generate perturbation effect inside the channel.Design/methodology/approachA set of numerical simulations were carried out by multiphysic interactions between the fluid behavior, external electric field, temperature field and convection-diffusion field to generate the pulsed AC electrothermal flow inside the channel. Behavior of electrode–electrolyte system is discussed using the electrical lumped circuit model.FindingsHighly efficient temperature gradients are generated by applying pulsed electric potential over the electrodes; as a result, efficient secondary flows form inside the channel. The proposed method increases the interfacial contact area between the fluids and enhances the molecular diffusion transport phenomena. Maximum temperature rise of 4.1 K is observed in the gap between the electrodes for 0.08 S/m fluid medium, where the electric field is much stronger than elsewhere. Velocity field and concentration analysis reveal high performance perturbation effects for the mixing process. The periodic stretching and folding effects increase the interfacial contact area between the fluids by using pulsed AC electrothermal flow. Based on the results, 83 per cent mixing efficiency is achieved for 0.08 S/m fluid medium with a microchannel length of 400 µm. Both the mixing efficiency and generated temperature rise increase by increasing the fluid ionic strength.Originality/valueThe ability to generate low temperature rise is very important for AC electrothermally driven fluidic chips such as immunoassay chips. In the present research, a novel actuation mechanism has been proposed to generate AC electrothermal manipulation mechanism and enhance the mixing efficiency by using pulsed AC electrothermal flow.

On-Chip Microparticle and Cell Washing Using Coflow of Viscoelastic Fluid and Newtonian Fluid.

This work investigates the on-chip washing process of microparticles and cells using coflow configuration of viscoelastic fluid and Newtonian fluid in a straight microchannel. By adding a small amount of biocompatible polymers into the particle medium or cell culture medium, the induced viscoelasticity can push particles and cells laterally from their original medium to the coflow Newtonian medium. This behavior can be used for particle or cell washing. First, we demonstrated on-chip particle washing by the size-dependent migration speed using coflow of viscoelastic fluid and Newtonian fluid. The critical particle size for efficient particle washing was determined. Second, we demonstrated continuous on-chip washing of Jurkat cells using coflow of viscoelastic fluid and Newtonian fluid. The lateral migration process of Jurkat cells along the channel length was investigated. In addition, the cell washing quality was verified by hemocytometry and flow cytometry with a recovery rate as high as 92.8%. Scanning spectrophotometric measurements of the media from the two inlets and the two outlets demonstrated that diffusion of the coflow was negligible, indicating efficient cell washing from culture medium to phosphate-buffered saline medium. This technique may be a safer, simpler, cheaper, and more efficient alternative to the tedious conventional centrifugation methods and may open up a wide range of biomedical applications.

An On-Chip Error Detection Method to Reduce the Post-Silicon Debug Time

Debug time has become a major issue in post silicon debug because of the increasingly complicated nature of circuit design. However, reducing debug time is a major challenge because of the limited size of the trace buffer used to observe internal signals in the circuit. This study proposes an on-chip error detection method to overcome this challenge. The on-chip process detects the error-suspect window using the pre-calculated golden data stored in the trace buffer. This allows the selective compaction and capture of the debug data in the trace buffer during the error-containing interval. As a result, reducing the number of debug sessions significantly reduces the total debug time. The experimental results on various debug cases show significant reductions in total debug time compared to previous work.