Parallel Chip Research Articles

Mechanism and Control Strategies for Current Sharing in Multi-Chip Parallel Automotive Power Modules

Multi-chip parallel power modules are highly favored in applications requiring high capacity and high switching frequency. However, the dynamic current imbalance between parallel chips caused by asymmetric layouts limits the available capacity. This paper presents a method to optimize dynamic current distribution by adjusting the lengths and connection points of bond wires. For the first time, a response surface model and nonlinear constraint optimization algorithm are introduced, along with parameter analysis based on finite element methods, to establish the response surface models for the parasitic inductance of bond wires and DBC (direct bonded copper). By leveraging the optimization goals for parasitic inductance and the analytical expressions of all response surfaces, the dynamic current sharing issue was transformed into a nonlinear constrained optimization problem. The solution to this optimization problem identified the optimal connection points for the bond wires, enhancing dynamic current sharing performance. Simulations and experiments were conducted, revealing that the optimized automotive-grade module exhibited a significant reduction in current differences between parallel branches, from 41.7% to 5.03% compared with the original design. This indicated that the proposed optimization scheme for adjusting bond wire connection points could significantly mitigate current disparities, thereby markedly improving current distribution uniformity.

The Mechanism of Short-Circuit Oscillations in Automotive-Grade Multi-Chip Parallel Power Modules and an Effective Mitigation Approach.

This paper presents an in-depth analysis of the oscillation phenomenon occurring in multi-chip parallel automotive-grade power modules under short-circuit conditions and investigates three suppression methods. We tested and analyzed two commercial automotive-grade power modules, one containing two chips and the other containing a single chip, and found that short-circuit gate oscillations were more likely to occur in multi-chip parallel packaged modules than in single-chip packaged modules. Through experimental and simulation analyses, we observed that gate oscillations were mainly caused by the interaction between internal parasitic parameters of the module and the external drive circuit, and we found that high drive resistance and low common emitter inductance between parallel chips could effectively suppress gate voltage oscillations. We also analyzed the two mainstream suppression schemes, increasing the drive gate resistance and placing the drive capacitors in parallel. Unfortunately, we found that these suppression schemes were not ideal solutions because both schemes changed the switching characteristics of the power module. As an alternative, we propose a simple and effective solution that involves adding parallel connections between the parallel chips. Simulation calculations showed that this optimized method reduced the emitter inductance between parallel chips in the upper bridge arm by about 30% and in the lower bridge arm by 35%. Through short-circuit experiments conducted at different DC bus voltages, it has been verified that the new optimized solution effectively resolves gate oscillation issues without affecting the switching characteristics of the power module.

Abstract 4212: Mimicking HCC complex biology and diverse treatment response in a patient-derived microfluidic model

Abstract Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is closely associated with progressive stages of liver diseases. Its transformation, survival, progression and metastasis have been associated with regulation mechanisms orchestrated by the tumor stroma. Patient differences in tumor composition and cellular signaling are reflected in the diversity of therapy response. Hence, comprehensive in vitro models that capture patient-specific tumor and stromal components are necessary to elucidate and evaluate anticancer therapy. Patient-derived dissociated HCC cells from eight different patients were combined with tumor-derived fibroblasts and endothelial cells within a microfluidic setup comprising 64 parallel chips in a microtiter plate format. Cultures were challenged with an individual or combinatorial treatment from a panel of tool compounds for 72 hours in an automated setup. We used immunofluorescence and high content confocal imaging to assess the structural and biological interaction between cancer cells and the associated stroma. Viability assessment, artificial intelligence-based vascular morphology characterization and multiplexed chemokine/cytokine release measurements were used to elucidate patient and drug-dependent effects of single or combinatorial treatments. Cellular interaction within the microfluidic platform led to a vascularized tumor construct, with hepatocellular carcinoma aggregates being enveloped and traversed by a lumenized and interconnected vascular plexus, in association with tumor-derived fibroblasts. Compound treatment led to profound differences across the tested parameters, indicating different anticancer effects in conjunction with the biological diversity of the patient material. Finally, morphological assessment revealed distinct compound-induced effects on the tumor’s vascular organization. We present a vascularized patient-derived HCC model that includes relevant cellular players of the tumor microenvironment found in vivo. These co-cultures are highly suitable for studying specific cell types as well as patient-specific responses. We envision that this system has the potential to provide a platform for understanding the interplay between different cell types present in hepatocellular carcinomas, with sufficient scalability ease of use for industrial and clinical implementation. Citation Format: Orsola Mocellin, Abbie Robinson, Aleksandra Olczyk, Stephane Treillard, Thomas Olivier, Chee P. Ng, Jeroen Heijmans, Arthur Stok, Gilles van Tienderen, Monique Verstegen, Sebastian J. Trietsch, Henriëtte L. Lanz, Paul Vulto, Jos Joore, Karla Queiroz. Mimicking HCC complex biology and diverse treatment response in a patient-derived microfluidic model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4212.

Current imbalance analysis of multichip influenced by parasitic inductance within PP-IEGT

The Press-Pack Injection Enhanced Gate Transistor (PP-IEGT) technology is frequently employed in converters for high power systems. In the device packaging, the imbalanced current sharing among chips has become a significant issue for device reliability. Considering the semiconductor structure of IEGT is different from the conventional power devices, the main prerequisite for fully quantifying the current distribution is to establish a suitable electrical model for IEGT. Thus, this paper proposes an IEGT single chip lumped-charge model taking into account the effect of carrier injection enhancement in the emitter. Furthermore, as for the parallel branches in PP-IEGT, the parasitic inductance of the drive board and pillars within the package are extracted by Ansys simulation, and the validity of Ansys simulation is verified by the port S-parameter method. Finally, combining the electrical model and the effect of mutual inductance, the switching inconsistency is evaluated. It is demonstrated that the farther the branch from the gate inlet, the greater the gate inductance withstands. Besides, the mutual inductance is an important factor to influence the electrical parameter distribution. Both mutual coupling coefficient and current density display degressive trends with the increases of the gap between parallel chips.

In Situ Diagnosis for IGBT Chip Failure in Multichip IGBT Modules Based on a Newly Defined Characteristic Parameter Low-Sensitive to Operation Conditions

To achieve the desired current capability, insulated gate bipolar transistor (IGBT) modules are normally composed of parallel chips. The bond wires fatigue on a certain chip will gradually cause the performance of the power module to degrade, and eventually lead to an unexpected catastrophic failure of the entire system. Therefore, this paper proposes an in-situ diagnosis method for bond wires fatigue in multichip IGBT modules based on a newly defined characteristic parameter. By sensitivity analysis, horizontal comparison and experimental test, the parameter was proven to have the advantages of being safe, low-sensitive to operation conditions and easy to extract. Correspondingly, the online monitoring circuit was designed on the basis of the voltage clamping technology, and further applied on an inverter prototype with 100 A peak current and 10 kHz switching frequency. The results showed that although with large change of junction temperature and load current, the proposed method can accurately diagnose IGBT chip failure by the sudden increase in the amplitude of the parameter. Moreover, the monitoring circuit can be both plug-and-play in the existing inverters and integrated in the gate drive circuit owing to the compact design, which is expected to avoid catastrophic failures of the inverter in field application.

Chitosan decorated essential oil nanoemulsions for enhanced antibacterial activity using a microfluidic device and response surface methodology

In this work, the antibacterial activity of Satureja Khuzestanica essential oil nanoemulsions improved by employing chitosan (ch/SKEO NE) against E. coli bacterium. The optimum ch/SKEO NE with mean droplet size of 68 nm was attained at 1.97, 1.23, and 0.10%w/w of surfactant, essential oil and chitosan, using Response Surface Methodology (RSM). Applying microfluidic platform, the ch/SKEO NE resulted in improved antibacterial activity owing to the modification of surface properties. The nanoemulsion samples showed a significant rupturing effect on the E. coli bacterial cell membrane which resulted in a rapid release of cellular contents. This action was remarkably intensified by executing microfluidic chip in parallel to the conventional method. Having treated the bacteria in the microfluidic chip for 5 min with a 8 μg/mL concentration of ch/SKEO NE, the bacterial integrity disrupted quickly, and the activity was totally lost in a 10-min period at 50 μglmL, while it took 5 h for a complete inhibition in the conventional method using the same concentration of ch/SKEO NE. It can be concluded that nanoemulsification of EOs using chitosan coating can intensify the interaction of nanodroplets with the bacterial membrane, especially within the microfluidic chips which provides high contact surface area.

TMET-09. LOSS OF MAT2A COMPROMISES METHIONINE METABOLISM AND REPRESENTS A VULNERABILITY IN H3K27M MUTANT GLIOMAS

Abstract H3K27-mutant diffuse midline gliomas (DMGs) are defined as grade IV tumors by the World Health Organization. DMGs are inoperable and resistant to chemo/radio therapies. Median survival ranges from 8-11 months, with 2% of patients surviving beyond 5 years. H3K27M mutations lead to global epigenetic and transcriptional reprogramming driven by global loss of negative transcriptional regulator H3K27 trimethylation (H3K27me3). Loss of H3K27me3 is an initiating event in gliomagenesis. This disease lacks appropriate models to predict disease biology and response to treatment. Therefore, we developed a novel syngeneic H3K27M mouse model. An unbiased integrated systems biology approach identified that H3K27M but not isogenic controls relied on the amino acid methionine and the enzyme Methionine Adenosyltransferase 2A (MAT2A). MAT2A is a central regulator of one-carbon metabolism by converting methionine to S-adenosylmethionine (SAM), the universal methyl-donor for protein and nucleotide methylation reactions. In complementary genetic approaches, we applied these findings to patient-derived cell lines with the H3K27M mutation. We hypothesize that MAT2A abrogation, genetic/pharmacological, would alter DMG viability by disrupting the methylome. The current MAT2A sensitivity paradigm is based on Methylthioadenosine Phosphorylase (MTAP) deletion through a synthetic lethal mechanism. We provide a novel mechanism whereby H3K27M cells are sensitive to MAT2A loss, independent of MTAP and through Adenosylmethionine Decarboxylase 1 (AMD1) overexpression disrupting MAT2A regulation. This results in H3K27M cells having lower MAT2A protein levels, conferring a sensitivity by inhibiting residual MAT2A. Genetic/pharmacological aberrations to MAT2A resulted in reduced proliferation. Parallel H3K36me3 ChIP and RNA-sequencing identified loss of oncogenic and developmental transcriptional programs associated with MAT2A loss. In vivo syngeneic and patient-derived xenograft models with both inducible MAT2A knockdown or methionine restricted diets showed extended survival. These results suggest novel interactions between methionine metabolism and the epigenome of H3K27M gliomas and provide evidence that MAT2A, presents exploitable therapeutic vulnerabilities in histone mutant gliomas.

Influence mechanism of solder aging and thermal network model optimization of multi-chip IGBT modules

With the continuous increase in the scale of new energy grid-connected, high-power converter IGBT modules are widely used in wind, solar, and other new energy power generation systems. The safe and reliable operation of IGBT modules with parallel chips is becoming more and more important. In the multi-chip module, uneven solder aging will increase the thermal resistance of some chips, which will lead to an inaccurate estimation of the junction temperature of the multi-chip IGBT power module. To this end, this paper proposes to use the reconstructed thermal impedance matrix to modify the multi-chip thermal network model and estimate the junction temperature. By analyzing the nonlinear accelerated deterioration law between the aging degree of the solder layer and the self-thermal impedance and coupled thermal impedance of the IGBT module, the influence mechanism of different solder layer aging degrees inside the module on the thermal conduction radius and thermal diffusion angle is clarified. The thermal impedance matrix is reconstructed with the modified thermal diffusion angle, thus realizing the optimization of the thermal network model of the multi-chip IGBT module. The experimental results show that the junction temperature calculation results of the improved multi-chip IGBT module thermal network model are more in line with the finite element simulation than the traditional unimproved method, thus verifying the validity and accuracy of the model, and laying a solid foundation for the large-scale integrated multi-chip thermal analysis. Theoretical basis.

Experimental Investigations on Current Sharing Characteristics of Parallel Chips Inside Press-Pack IGBT Devices

Press-pack insulated gate bipolar transistor (IGBT) devices have multiple chips paralleled to enhance their power density. However, the current imbalance among chips limits the increase of the power, which is mainly attributed to external factors, like stray inductance, temperature, and mechanical pressure. Besides, for the difficulties in decoupling multiple external factors, the current imbalance in press-pack IGBT devices has been extensively studied by simulation, and lack of experimental investigations. In this article, a multifactor decoupling experimental approach for the current sharing characteristics is proposed. The stray inductance, temperature, and mechanical pressure of the two parallel branches can be adjusted independently for investigating chips’ current sharing. Then, the experimental platform for the parallel 3.3 kV/50 A IGBT chips under differentiated external factors is implemented. Measured results show that the stray inductance affects the transient current sharing during turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> greatly, and the maximum current imbalance can reach 25.46%. The temperature mainly affects the steady state and the maximum current imbalance is 11.7%. Otherwise, mechanical pressure is negligible on the steady and transient current imbalances, which are less than 3%. Finally, the influence mechanisms of the external factors are proposed to explain the current sharing characteristics of parallel chips.

Evaporation of confined droplet between parallel chips with varying gap at room temperature

A theoretical study and experimental validation of the evaporation of a droplet confined between two parallel square chips with a free-standing top chip over a water meniscus is presented in this article. The analytical model describes the surface area of a negatively curved liquid–air interface, and the evaporation model was thus solved for this case. The dynamics of decreasing the gap between the two parallel chips show a linear dependency in time at room temperature. Two main regimes are observed in this case, the constant wetted area regime and the varying wetted area regime. The theoretical study was lastly validated through experiments.

A Novel Approach to Model and Analyze Uneven Temperature Distribution Among Multichip High-Power Modules and Corresponding Method to Respecify Device SOA

As the most widely used power semiconductor devices, insulated gate bipolar transistor (IGBT) modules are normally composed of parallel IGBT chips to achieve the desired current capability. However, the electrothermal behavior of each chip is significantly different due to the asymmetric layout, increasing the overheating risk of single chip. Therefore, this article proposes a novel approach to describe the thermal safe operation area of multichip IGBT modules in the inverter application, considering the uneven temperature distribution among parallel chips. The novelty of the approach is that it applied the proposed analytical model describing the uneven electrothermal behavior, thus avoiding the traditional averaging process. Comprehensive investigation has been made to reveal the deep mechanism of the inconsistent temperature distribution, which are the uneven dynamic current sharing and thermal cross-coupling effects. Correspondingly, the analytical model of the uneven switching loss and the standard form of thermal resistance matrix related to cooling performance are proposed and further verified, respectively. Based on the proposed approach, the recommended operation area of different rated devices is fully described. The contribution of this article enables more well-founded device selection to achieve a safe and cost-efficient design for the inverter application.

Monitoring Initial Solder Layer Degradation in a Multichip IGBT Module via Combined TSEPs

With the development of high power converters, the safe operation of large IGBT modules with parallel chips is of increasing importance. In a multichip module, uneven solder layer degradation translates into higher thermal resistance for some of the chips, leading to junction temperature differences between them. However, the specific meaning of a virtual junction temperature extracted from any external electric characteristic parameter of the module is not yet clear. This paper studies the physical meanings of the temperatures estimated by the threshold voltage and the Miller platform duration as well as the quasi turn- off delay time. Experimental results show that the temperature estimated from the threshold voltage is close to the highest temperature of all the chips, while that estimated from the Miller platform duration or quasi turn-off delay time is close to the average chip temperature. Making use of the difference between the two, this paper proposes a new method to monitor the initial solder layer degradation in the multichip IGBT module. Such a method using combined temperature sensitive electric parameters (TSEPs) is verified for different levels of degradation.

Modeling ischemic stroke in a triculture neurovascular unit on-a-chip

BackgroundIn ischemic stroke, the function of the cerebral vasculature is impaired. This vascular structure is formed by the so-called neurovascular unit (NVU). A better understanding of the mechanisms involved in NVU dysfunction and recovery may lead to new insights for the development of highly sought therapeutic approaches. To date, there remains an unmet need for complex human in vitro models of the NVU to study ischemic events seen in the human brain.MethodsWe here describe the development of a human NVU on-a-chip model using a platform that allows culture of 40 chips in parallel. The model comprises a perfused vessel of primary human brain endothelial cells in co-culture with induced pluripotent stem cell derived astrocytes and neurons. Ischemic stroke was mimicked using a threefold approach that combines chemical hypoxia, hypoglycemia, and halted perfusion.ResultsImmunofluorescent staining confirmed expression of endothelial adherens and tight junction proteins, as well as astrocytic and neuronal markers. In addition, the model expresses relevant brain endothelial transporters and shows spontaneous neuronal firing. The NVU on-a-chip model demonstrates tight barrier function, evidenced by retention of small molecule sodium fluorescein in its lumen. Exposure to the toxic compound staurosporine disrupted the endothelial barrier, causing reduced transepithelial electrical resistance and increased permeability to sodium fluorescein. Under stroke mimicking conditions, brain endothelial cells showed strongly reduced barrier function (35-fold higher apparent permeability) and 7.3-fold decreased mitochondrial potential. Furthermore, levels of adenosine triphosphate were significantly reduced on both the blood- and the brain side of the model (4.8-fold and 11.7-fold reduction, respectively).ConclusionsThe NVU on-a-chip model presented here can be used for fundamental studies of NVU function in stroke and other neurological diseases and for investigation of potential restorative therapies to fight neurological disorders. Due to the platform’s relatively high throughput and compatibility with automation, the model holds potential for drug compound screening.

A novel double-sided cooling packaging structure of SiC-based half bridge module integrating the laminated busbar

This paper presents a novel double-sided cooling SiC-based half-bridge (HB) module with laminated busbar. The novelty of this module lies in the integration of a laminated busbar which can result in a significant reduction of the module parasitic inductance. Moreover, a 3D vertical structure design can reduce the commutation loop area inside the module, thereby further achieving a lower commutation loop inductance. Meanwhile, this module achieves wire-free bonding that can improve the reliability of the power module to a certain extent. A fan-shaped DBC layout is designed to ensure the symmetrical layout of the paralleled chips, which can realize a better current sharing performance. In fact, an unbalanced junction temperature can also affect the current balance of each parallel device, resulting in unequal turn-on and turn-off losses. Therefore, a three-outlet circular water-cooled heat sink is proposed to ensure the junction temperature balance of the parallel chips, which is demonstrated by thermal simulation. Then, by the Ansys Q3D, the extracted parasitic inductance of the module is about 5.63 nH, and the imbalance degree between each parallel branch is about 5.8%. Finally, the low parasitic inductance and highly symmetry of the module are verified by the experimental tests.

Active droplet-array microfluidics-based chemiluminescence immunoassay for point-of-care detection of procalcitonin

The application of conventional chemiluminescence immunoassay (CLIA) in resource-limited settings is limited due to the large apparatus footprint, cumbersome operation and maintenance process, and high consumption of reagents. To address this issue, we developed an active droplet-array (ADA) microfluidics-based CLIA system, which consists of a compact microchip analyzer and microfluidic chips with preloaded reagents. The microfluidic chip contains microslit-connected microchambers, in which all the required reagents were preloaded in water-in-oil droplets. The microfluidic chip analyzer can manipulate five microfluidic chips in parallel in a single run. By interacting the microchip with magnetic, thermal, optical mechanisms programmatically, the entire workflow of CLIA can be accomplished in an automated manner. With the proposed CLIA, the detection of procalcitonin (PCT) can be completed in 12 min, with a limit of detection (LOD) of 0.044 ng mL−1 and a detection range from 0.044 to 100 ng mL−1. We found a good linear correlation between the microfluidic CLIA and the conventional electrochemiluminescence immunoassay (R2=0.98).The microfluidic CLIA has significant advantages over the conventional ELISA in detection sensitivity, dynamic range, instrument size and turnaround time, and can provide more consistent and reliable results than the lateral flow immunoassays. The compact microfluidic system can perform automated and parallelized CLIA in a short turnaround time, and thus well suited to Point-of-Care detection of disease biomarkers.

Extremely High-Throughput Parallel Microfluidic Vortex-Actuated Cell Sorting.

We demonstrate extremely high-throughput microfluidic cell sorting by making a parallel version of the vortex-actuated cell sorter (VACS). The set-up includes a parallel microfluidic sorter chip and parallel cytometry instrumentation: optics, electronics and control software. The result is capable of sorting lymphocyte-sized particles at 16 times the rate of our single-stream VACS devices, and approximately 10 times the rate of commercial cell sorters for an equivalent procedure. We believe this opens the potential to scale cell sorting for applications requiring the processing of much greater cell numbers than currently possible with conventional cell sorting.

(Invited) Micro-Transfer-Printing at X-FAB: Demonstration of a New Technology for Wafer-Level Packaging

Introduction Within this publication micro-transfer-printing (µTP) will be introduced as a promising new technology for 3D wafer-level packaging (WLP). The main advantage of µTP arises from the substantial parallel chip transfer from the source wafer to a target device by a visco-elastic stamp. To execute and develop this versatile technology a pilot line has been installed in the X-FAB MEMS Foundry GmbH clean room facilities within a funded EU project (MICROPRINCE). To demonstrate the general process capabilities recent results on the preparation and integration of silicon-based ICs, optical filters and III/V semiconductors shall be discussed. Contents The general principle of µTP is based on the utilization of an elastomer stamp to transfer devices or arrays of devices from their native substrate (source) to a non-native target material [1]. A mandatory requirement for this transfer is that the stamp, typically made of polydimethylsiloxane (PDMS), provides tunable adhesion properties to the printable chiplet [2]. Thereby, high adhesion during the “pick-up” as well as low adhesion forces during the “placing” steps can be achieved.The general process flow for micro-transfer-printing is illustrated in Figure 1 .Therein, the main advantage of µTP, namely the extensive parallelization of the chip placement (schematics a.-e.), can be recognized. Such a parallelization offers the possibility of a major process time reduction.Prior to the transfer operation, the source wafer has to be prepared for the printing process. This involves the formation of reliable anchor and tether structures which carry the printable chiplets after the release etch. Another crucial requirement on these structures is that they provide a controlled micro-fracture and release the transfer chiplets to the stamp [3]. An example of a print-ready optical filter device is furthermore illustrated in Figure 1g.The target on the other hand has to be coated with an adhesion providing polymer (see red layer in Figure 1d.-f.) for which bisbenzocyclobutene (BCB) is applied at X-FAB.After the printing itself, a post-processing comprising the patterning of applied adhesion media, a wiring via a Cu redistribution layer (RDL) and a passivation is required to allow the functionality of active devices (see Figure 1f.). Figure 1h shows two 3D-integrated demonstrator devices which have been printed on a XL035 technology from X-FAB and which were afterwards connected via a Cu-RDL layer. Within the printing experiments of these chiplets a print yield of about 99.9% with a placement accuracy of down to 3σ ≤ 0.78µm has been achieved. Conclusions By this publication the Micro-transfer-printing (µTP) technology and its technical implementation will be introduced. To build up and develop µTP processes a pilot line has been installed in the X-FAB MEMS Foundry GmbH via a funded ECSEL project called “MICROPRINCE”. To execute the µTP technology for 3D integration several process steps have to be executed to prepare a source wafer for the printing operation, transfer the chiplets to a non-native target and connect them afterwards during the prost-processing. The process sequence itself will be explain in more detail within the presentation on examples of optical filters, silicon ASICs as well as III/V semiconductor chiplets. Acknowledgements This work is funded by ECSEL JU under grant agreement No 737465 and by the BMBF No ESECS16204. Further, the authors like to thank all X-FAB internal and external MICROPRINCE partners for their support.

Doxorubicin Enhances Procoagulant Activity of Endothelial Cells after Exposure to Tumour Microparticles on Microfluidic Devices

The majority of cancer patients undergoing chemotherapy have a significantly increased risk of venous thromboembolism via a mechanism not yet fully elucidated but which most probably involves tumour microparticles (MP) combined with damaged/activated endothelium. Tumour cell lines (ES-2 and U87) were cultured as 3D spheroids and transferred to biochips connected through to a second chip precultured with an endothelial cell layer (human umbilical vein endothelial cells [HUVECs]). Media were introduced with and without doxorubicin (DOX) to the spheroids in parallel chips under constant flow conditions. Media samples collected pre- and post-flow through the biochip were analysed for tissue factor microparticles (TFMP) and procoagulant activity (PCA). HUVECs were also harvested and tested for PCA at a constant cell number. TFMP levels in media decreased after passing over HUVECs in both conditions over time and this was accompanied by a reduction in PCA (indicated by a slower coagulation time) of the media. The relationship between PCA and TFMP was correlated (r = −0.85) and consistent across experiments. Harvested HUVECs displayed increased PCA when exposed to tumour spheroid media containing TFMP, which was increased further after the addition of DOX, suggesting that the TFMP in the media had bound to HUVEC cell surfaces. The enhanced PCA of HUVECs associated with the DOX treatment was attributed to a loss of viability of these cells rather than additional MP binding. The data suggest that tumour MP interact with HUVECs through ligand-receptor binding. The model described is a robust and reproducible method to investigate cytotoxic agents on tumour spheroids and subsequent downstream interaction with endothelial cells.

Mobile sensor based human activity recognition: distinguishing of challenging activities by applying long short-term memory deep learning modified by residual network concept.

Automated recognition of daily human tasks is a novel method for continuous monitoring of the health of elderly people. Nowadays mobile devices (i.e. smartphone and smartwatch) are equipped with a variety of sensors, therefore activity classification algorithms have become as useful, low-cost, and non-invasive diagnostic modality to implement as mobile software. The aim of this article is to introduce a new deep learning structure for recognizing challenging (i.e. similar) human activities based on signals which have been recorded by sensors mounted on mobile devices. In the proposed structure, the residual network concept is engaged as a new substructure inside the main proposed structure. This part is responsible to address the problem of accuracy saturation in convolutional neural networks, thanks to its ability in jump over some layers which leads to reducing vanishing gradientseffect. Therefore the accuracy of the classification of several activities is increased by using the proposed structure. Performance of the proposed method is evaluated on real life recorded signals and is compared with existing techniques in two different scenarios. The proposed structure is applied on two well-known human activity datasets that have been prepared in university of Fordham. The first dataset contains the recorded signals which arise from six different activities including walking, jogging, upstairs, downstairs, sitting, and standing. The second dataset also contains walking, jogging, stairs, sitting, standing, eating soup, eating sandwich, and eating chips. In the first scenario, the performance of the proposed structures is compared with deep learning schemes. The obtained results show that the proposed method may improve the recognition rate at least 5% for the first dataset against its own family alternatives in distinguishing challenging activities (i.e. downstairs and upstairs). For the second data set similar improvements is obtained for some challenging activities (i.e. eating sandwich and eating chips). These superiorities even reach to at least 28% when the capability of the proposed method in recognizing downstairs and upstairs is compared to its non-family methods for the first dataset. Increasing the recognition rate of the proposed method for challenging activities (i.e. downstairs and upstairs, eating sandwich and eating chips) in parallel with its acceptable performance for other non-challenging activities shows its effectiveness in mobile sensor-based health monitoring systems.

Elastic Half-Space Theory-Based Distributed-Press-Pack Packaging Technology for Power Module With Balanced Thermal Stress

In this article, the distributed-press-pack (DPP) packaging technology is developed to achieve balanced thermal stress on the chips. Under the current lumped-press-pack (LPP) style, the mechanical stress distribution on the chips, which is inherently uneven and coupled with thermal stress distribution, can be described with elastic half-space theoretical model. By decentralizing the lumped pressing load and positioning the loads evenly, a matrix of clamping array is formulated, and the mechanical stress distribution is compared under different clamping ways. Then a 3×3 clamping method that meets the trade-off between the balanced stress distribution and the packaging cost is chosen. Meanwhile, the busbar and heatsinks are integrated to improve the power density of the power module. Finally, a DPP prototype is implemented. By varying the pressure around the chips and heating them, the thermal distribution between parallel chips inside the prototype is compared and the effect of the proposed elastic half-space theory-based DPP packaging technology on the thermal stress balance is verified.