Carbon Nanotube Carpets Research Articles

Hierarchical hybrid heat sink material for thermo-electric generators

This short communication focuses on the impact of enhancing heat sink effectiveness of thermoelectric generators (TEG) by attaching covalently bonded carpet-like arrays of carbon nanotubes on prefabricated copper structures. Structural hierarchy of heat sinks are important for synergizing the thermal conductivity of materials with fin architectures tailored for active or passive electronic cooling components. We investigated strategic integration of carefully aligned carpets of carbon nanotubes (CNTs) on heat sink fins to simultaneously enhance conductive, convective, and radiative heat transfer pathways. Carbon nanotubes (CNT) combine ultra-high thermal conductivity along their axial directions with high surface area and radiative heat transfer coefficients. While CNTs are known to enhance nanofluidic coolants and thermal interface composites, their full potential can only be utilized if they are aligned normal to heat sink fins, and strongly anchored to retain the fin/radiator architecture in service conditions. This study focused on measuring the direct impact of CNT carpet on TEG performance under ambient passive cooling conditions without adding any noticeable weight or volume to the heat sink. It was seen that this single step of CNT attachment on the surface could increase the open circuit voltage of TEG modules by over 50% in the passive mode with respect to original untreated heat sink, and over 100% with respect to no heat sink. This improvement may be enhanced even further by introducing forced coolants. These results therefore show significant promise in using the surface nanocarpet approach for development of compact, lightweight, robust and reusable solid-state heat sinks in future.

Bioinspired Hierarchical Carbon Structures as Potential Scaffolds for Wound Healing and Tissue Regeneration Applications.

Engineered bio-scaffolds for wound healing provide an attractive treatment option for tissue engineering and traumatic skin injuries since they can reduce dependence on donors and promote faster repair through strategic surface engineering. Current scaffolds present limitations in handling, preparation, shelf life, and sterilization options. In this study, bio-inspired hierarchical all-carbon structures comprising carbon nanotube (CNT) carpets covalently bonded to flexible carbon fabric have been investigated as a platform for cell growth and future tissue regeneration applications. CNTs are known to provide guidance for cell growth, but loose CNTs are susceptible to intracellular uptake and are suspected to cause in vitro and in vivo cytotoxicity. This risk is suppressed in these materials due to the covalent attachment of CNTs on a larger fabric, and the synergistic benefits of nanoscale and micro-macro scale architectures, as seen in natural biological materials, can be obtained. The structural durability, biocompatibility, tunable surface architecture, and ultra-high specific surface area of these materials make them attractive candidates for wound healing. In this study, investigations of cytotoxicity, skin cell proliferation, and cell migration were performed, and results indicate promise in both biocompatibility and directed cell growth. Moreover, these scaffolds provided cytoprotection against environmental stressors such as Ultraviolet B (UVB) rays. It was seen that cell growth could also be tailored through the control of CNT carpet height and surface wettability. These results support future promise in the design of hierarchical carbon scaffolds for strategic wound healing and tissue regeneration applications.

Carbon Nanotubes Substrates Alleviate Pro-Calcific Evolution in Porcine Valve Interstitial Cells.

The quest for surfaces able to interface cells and modulate their functionality has raised, in recent years, the development of biomaterials endowed with nanocues capable of mimicking the natural extracellular matrix (ECM), especially for tissue regeneration purposes. In this context, carbon nanotubes (CNTs) are optimal candidates, showing dimensions and a morphology comparable to fibril ECM constituents. Moreover, when immobilized onto surfaces, they demonstrated outstanding cytocompatibility and ease of chemical modification with ad hoc functionalities. In this study, we interface porcine aortic valve interstitial cells (pVICs) to multi-walled carbon nanotube (MWNT) carpets, investigating the impact of surface nano-morphology on cell properties. The results obtained indicate that CNTs significantly affect cell behavior in terms of cell morphology, cytoskeleton organization, and mechanical properties. We discovered that CNT carpets appear to maintain interfaced pVICs in a sort of “quiescent state”, hampering cell activation into a myofibroblasts-like phenotype morphology, a cellular evolution prodromal to Calcific Aortic Valve Disease (CAVD) and characterized by valve interstitial tissue stiffening. We found that this phenomenon is linked to CNTs’ ability to alter cell tensional homeostasis, interacting with cell plasma membranes, stabilizing focal adhesions and enabling a better strain distribution within cells. Our discovery contributes to shedding new light on the ECM contribution in modulating cell behavior and will open the door to new criteria for designing nanostructured scaffolds to drive cell functionality for tissue engineering applications.

In Situ Internal Strengthened Carbon Nanotube Carpets on Graphene for Anti-Icing Application

In Situ Internal Strengthened Carbon Nanotube Carpets on Graphene for Anti-Icing Application

Hierarchical nanostructured surface design for robust and flexible multifunctional devices

This paper investigates structural and functional properties of a hierarchical hybrid flexible material with nanostructured surface architecture. These solids comprise of carpet-like arrays of covalently bonded carbon nanotubes (CNT) on the surface of strong and flexible carbon fabric. In-depth analysis of the multi-scale morphology of this structure is provided, with emphasis on structure-property relationships relevant to surface-interaction related applications such as catalysis, sensing, microfluidics and bio-scaffolding devices. A two-step process is used to anchor carbon nanotubes directly on the surface of carbon fiber cloth, and its morphology, structure and surface chemistry analyzed in detail. Surface structure model from structural and physical property measurements predict over 2000 times increase in specific surface area (SSA) of the fabric due to CNT carpet growth. This estimate is in good agreement with direct SSA measurement using Brunauer–Emmett–Teller (BET) gas-adsorption technique, indicating full utilization of the CNT surface sites, which can be used for adsorption, functionalization, thermal or electrical transport. Electrical measurement of these materials shows a systematic increase of sheet conductivity of the fabric with increasing CNT carpet height. These results indicate that this type of material design can combine the structural durability and flexibility of advanced fabrics with the enhanced surface activity of nanomaterials for a wide variety of surface interaction devices of the future.

Boosting the charge transfer efficiency of metal oxides/carbon nanotubes composites through interfaces control

Metal oxide/carbon materials composites (MOx/C) are broadly used as electrodes in energy storage devices. However, their capacity under high rates is limited due to the sluggish ion/electron transportation during faradaic reactions. In this work, carbon nanotube carpets (CC)/Fe2O3 nanoparticles covered with bud-liked carbon layer (CC/Fe2O3@b-C) is developed as an electrode by interfaces design. It is found that the bud-liked carbon wrapper enlarges interface area and provides an accelerated conducting network between CC and Fe2O3 nanoparticles through “seamless” connection. With boosted charge transfer efficiency, this composite demonstrates an excellent rate capability. The CC/Fe2O3@b-C electrode shows a high capacity of 246.15 mC cm−2 under 5 mV s−1 and can maintain ~95% when the scan rate is increased to 100 mV s−1. Moreover, the hybrid device paired with carbon fiber cloth (CFC)/Co(OH)2 cathode exhibits simultaneous high energy density and power density, showing good potential application in high-power devices.

Flexible reusable hierarchical hybrid catalyst for rapid and complete degradation of triclosan in water

A flexible, durable, and reusable nanocatalyst system was fabricated by anchoring palladium nanoparticles on carbon nanotube (CNT) carpets covalently attached to carbon cloth. These hierarchical hybrid materials were tested for catalytic degradation of triclosan (TCS), an emerging contaminant. Materials were characterized using scanning & transmission electron microscopy techniques (SEM and TEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). The reaction kinetics was studied using HPLC and reaction pathways proposed based on LC-MS/GC-MS analyses. In the presence of hydrogen, complete step-wise chlorine removal was seen until complete dechlorination was accomplished. The pseudo-first-order rate constant was measured to be orders of magnitude higher than earlier reported values. Moreover, the same material was usable for multiple cycles in flowing water. This study demonstrates that robustness and reusability of larger structural materials can be combined with the ultra-high surface activity of nanocatalysts to provide practical and eco-friendly solutions for water sustainability.

A Flexible Pressure Sensor With Sandwiched Carpets of Vertically Aligned Carbon Nanotubes Partially Embedded in Polydimethylsiloxane Substrates

This paper presents a flexible pressure sensor composed of two face-to-face electrodes of vertically aligned carbon nanotubes (VACNTs) carpets partially embedded in polydimethylsiloxane(PDMS) substrates. VACNTs were grown using atmospheric pressure chemical vapor deposition (APCVD) on a Si/SiO2 substrate and transferred onto PDMS for partial embedment. This unique synthesis permitted a rapid and facile integration of a flexible and stretchable platform for the pressure sensor. The change of resistance occurs due to the external pressure applied orthogonal to the surface. The substrate was stretched to 180% and bent at bending radii of 87 mm and 105 mm. The pressure sensor exhibited the response times of 40 ms during loading and 60 ms during unloading. As a proof-of-concept, the sensor was attached on human skin; the heart rate, muscle flexing, and walking signals of an individual have been measured. In respect to durability, this sensor also showed a stable performance for 10,000 loading/unloading cycles with a resistance retention of 82% demonstrating its long-term use for repeated cycles toward practical applications.

Efficient Growth of Carbon Nanotube Carpets Enabled by In Situ Generation of Water

Catalytic chemical vapor deposition (CVD) utilizing the gaseous product mixture of Fischer–Tropsch synthesis (FTS-GP) offers the potential for scale-up and controlled growth of carbon nanotube (CNT...

Magnesia and Magnesium Aluminate Catalyst Substrates for Carbon Nanotube Carpet Growth

Carbon nanotube (CNT) carpet growth behavior is systematically investigated on a pristine and ion beam-bombarded family of basic catalyst substrates: MgAl2O4 (100), MgAl2O4 (110), MgAl2O4 (111), an...

Multi-walled carbon nanotube carpets as scaffolds for U87MG glioblastoma multiforme cell growth.

Carbon Nanotubes (CNTs) are known for effective adhesion, growth, and differentiation of bone, muscle, and cardiac cells. CNTs can provide excellent mechanical and electrical properties for cell scaffolding; however, loose CNTs can cause in-vivo toxicity. To suppress this risk, our team has developed biomimetic scaffolds with multiscale hierarchy where carpet-like CNT arrays are covalently bonded to larger biocompatible substrates. In this study, we investigated the interaction between glioblastoma multiforme (GBM) cells (U87MG) and our unique hierarchical CNT-coated scaffolds upon brain tumor cell proliferation. U87MG cells grown on un-modified carbon scaffolds grew in a bi-phasic fashion. Initially, the scaffolds prevented GBM cell growth; however, prolonged growth on such scaffolds significantly increased GBM cell proliferation. We further defined the importance of the hydrophobicity/hydrophilicity of the CNT-coated scaffolds in this cellular response by utilizing sodium-hypochlorite based bleach treatment prior to cellular exposure. This surface modification increased the hydrophilicity of the CNT-coated scaffolds and ameliorated the biphasic response of U87MG cells allowing for a normal growth curve. Findings highlight the importance of surface modification and wettability of the CNT-coated scaffolds for cell growth applications. The focus for this study was to determine whether scaffold surface features could modulate tumor-scaffold interactions, and thus to improve our understanding of and optimize successful development of future scaffold-based chemotherapy applications. Overall, it appears that the wettability of carbon scaffolds coated with CNTs is an important regulator of U87MG cellular growth. These findings will be important to consider when developing a potential chemotherapy-attached implant to be used post-surgical resection for GBM patient treatment.

High-efficiency adsorption for both cationic and anionic dyes using graphene nanoribbons formed by atomic-hydrogen induced single-walled carbon nanotube carpets

Carbonaceous materials are considered as potential adsorbents for organic dyes due to their unique structures which provide high aspect ratios, hydrophobic property, large efficient surface area, and easy surface modification. In this work, graphene nanoribbons (GNRs) were prepared by atomic hydrogen-induced treatment of single-walled carbon nanotube (SWCNTs), which inspire the idea of cutting and unzipping the SWCNTs carpets with the modified in molecules prevent because of the unfolding of the side-walls. The unfolded spaces and uniform vertical arrangement not only enhance the active surface area, but also promote the electrostatic and π–π interactions between dyes and GNRs. The improved adsorption capacity of GNRs beyond original SWCNTs can be determined by the adsorption kinetics and isotherm, which are evaluated through adsorption batch experiments of the typical cationic methylene blue (MB) and anionic orange II (OII) dye, respectively. It is shown that the adsorption kinetics follow a pseudo second-order model while the adsorption isotherm could be determined by Langmuir model. The results reveal that the maximum adsorption capacities of GNRs for MB and OII are 280 and 265 mg/g, respectively. The GNRs present the highly efficient, cost effective, and environmental friendly properties for the commercial applications of wastewater treatment.

Transparent carbon nanotubes promote the outgrowth of enthorino-dentate projections in lesioned organ slice cultures.

The increasing engineering of carbon-based nanomaterials as components of neuroregenerative interfaces is motivated by their dimensional compatibility with subcellular compartments of excitable cells, such as axons and synapses. In neuroscience applications, carbon nanotubes (CNTs) have been used to improve electronic device performance by exploiting their physical properties. Besides, when manufactured to interface neuronal networks formation in vitro, CNT carpets have shown their unique ability to potentiate synaptic networks formation and function. Due to the low optical transparency of CNTs films, further developments of these materials in neural prosthesis fabrication or in implementing interfacing devices to be paired with in vivo imaging or in vitro optogenetic approaches are currently limited. In the present work, we exploit a new method to fabricate CNTs by growing them on a fused silica surface, which results in a transparent CNT-based substrate (tCNTs). We show that tCNTs favor dissociated primary neurons network formation and function, an effect comparable to the one observed for their dark counterparts. We further adopt tCNTs to support the growth of intact or lesioned entorhinal-hippocampal complex organotypic cultures (EHCs). Through immunocytochemistry and electrophysiological field potential recordings, we show here that tCNTs platforms are suitable substrates for the growth of EHCs and we unmask their ability to significantly increase the signal synchronization and fiber sprouting between the cortex and the hippocampus with respect to Controls. tCNTs transparency and ability to enhance recovery of lesioned brain cultures, make them optimal candidates to implement implantable devices in regenerative medicine and tissue engineering.

Investigation of the surface properties of different highly aligned N-MWCNT carpets

We investigated the physicochemical surface properties of different highly aligned nitrogen-doped multi-walled carbon nanotube (N-MWCNT) carpets, synthesized using toluene/pyrazine, toluene/benzylamine and acetonitrile via a sublimation-based chemical vapor deposition (SCVD) method at 760 °C. The surfaces of the N-MWCNT carpets synthesized using toluene/pyrazine and toluene/benzylamine were very hydrophobic. In contrast, we observed a complete wetting of the N-MWCNT carpets synthesized using acetonitrile. The difference in the wetting behavior of these N-MWCNT carpets is the main focus in this study and was not investigated before. Here, we show that not only the presence or concentration of nitrogen inside the carbon lattice, but especially it's kind of incorporation have an important influence on the surface polarity.

Flexible Electrodes and Sensors Insensitive to Lateral Strains for Electronic Skin

Applying stretching-insensitive flexible and stretchy devices into flexible electronics would benefit a wide range of applications in wearable and multifunctional electronics, including flexible displays, curved smart phones, electronic skins, and implantable medical devices. If flexible devices are used for skin-attachable electronic devices, the devices can be subjected to mechanical deformation. Therefore, devices insensitive to lateral strains induced by mechanical deformation (such as stretching, bending, twisting and wrinkling) needs to be developed. In this work, we present a flexible and stretchy pressure sensor utilizing vertically aligned carbon nanotube (VACNT) carpets on Polydimethylsiloxane (PDMS)substrate, which reliably operates under dynamic deformations of the substrate such as stretching, bending, and twisting. We also present a flexible and stretchysupercapacitor composed of VACNTs partially embedded into PDMS. The devices are facilely fabricated by the partial-embedding of VACNTs in PDMS, permitting a strong hold of VACNT hybrid into PDMS, which facilitates a stable performance under varied strains. We synthesized VACNTs using atmospheric-pressure chemical vapor deposition (APCVD) into carpet-like structures. The catalyst layer consisting of 5 nm Al and 3 nm Fe was deposited on the Si/SiO₂ substrate prepared using physical vapor deposition (PVD). Then the substrate was placed in the atmosphere pressure chemical vapor deposition (APCVD) chamber. The furnace temperature was increased to 750˚C with a constant 500 sccm Ar flow. VACNTs were grown at 750˚C for 15 minutes with 60 sccm H₂ and 100 sccm C₂H₄. Then the chamber was cooled down to the room temperature while maintaining the same Ar flow rate. The structure of the grown CNTs is vertically aligned in general, while the individual carbon nanotubes are entangled with each other. The morphology of the VACNTs were characterized using scanning electron microscopy (SEM). To fabricate flexible substrates with embedded VACNTs, we transferred the grown VACNTs onto partially cured PDMS. First, we used a liquid mixture of PDMS base and curing agent (Sylgard 184 Silicone Elastomer, Dow Corning) which were mixed with a ratio of 10:1 to form a PDMS substrate. After degasing under reduced pressure in a vacuum pump, the bubbles were all removed while PDMS was still liquid. Then the liquid PDMS was placed on a hot plate at 65˚C for about 30 minutes before it was fully cured. We optimized the curing condition of PDMS, where the partially cured PDMS was tacky but not fully wet. The grown VACNTs were then placed onto partially cured PDMS. Then the tips of CNTs were partially immersed into PDMS slowly. During the curing process, the embedded CNTs were eventually wetted by PDMS. Then after PDMS was fully cured, the VACNT-PDMS structure was successfully peeled off from the Si/SiO₂ substrate owing to the strong adhesion between PDMS and VACNTs. The entire fabrication process is rapid and facile, which permits the integration of VACNT-PDMS substrate. For the pressure sensing, we applied three different pressure values to the sensor, 1.03 kPa (10g), 1.37 kPa (20g), and 1.82 kPa (50g), respectively. Various stretching and bending strains were applied to the VACNT-PDMS substrate. The substrate was laterally stretched to 200% and bent up to 180 degree under a constant pressure applied vertically against the substrate, demonstrating the consistent resistance up to 50% stretching and 180˚ bending. For the supercapacitor, the cyclic voltammetry (CV) showed good electrochemical stability and capacitive behaviors at scanning rate of 1000 mV/s. The capacitance can be calculated to be 2 mF/cm² at 1000 mV/s.

Aligned Carbon Nanotube Arrays Bonded to Solid Graphite Substrates: Thermal Analysis for Future Device Cooling Applications

Carbon nanotubes (CNTs) are known for high thermal conductivity and have potential use as nano-radiators or heat exchangers. This paper focuses on the thermal performance of carpet-like arrays of vertically aligned CNTs on solid graphite substrates with the idea of investigating their behavior as a function of carpet dimensions and predicting their performance as thermal interface material (TIM) for electronic device cooling. Vertically aligned CNTs were grown on highly oriented pyrolytic graphite (HOPG) substrate, which creates a robust and durable all-carbon hierarchical structure. The multi-layer thermal analysis approach using Netzsch laser flash analysis system was used to evaluate their performance as a function of carpet height, from which their thermal properties can be determined. It was seen that the thermal resistance of the CNT array varies linearly with CNT carpet height, providing a unique way of decoupling the properties of the CNT carpet from its interface. This data was used to estimate the thermal conductivity of individual multi-walled nanotube strands in this carpet, which was about 35 W/m-K. The influence of CNT carpet parameters (aerial density, diameter, and length) on thermal resistance of the CNT carpet and its potential advantages and limitations as an integrated TIM are discussed.

Elastic modulus measurements of vertically aligned multi walled carbon nanotubes carpets by using the nanoindentation technique

Electrical, thermal and mechanical properties of Vertically Aligned Multi Walled Carbon NanoTubes (VA-MWCNT) make them an ideal candidate to replace some of conventional materials in micro and nano-electronic components. Integrating this material in micro components requires a good knowledge of their properties. As the electrical and thermal properties, the MWCNT mechanical properties are difficult to assess. Several techniques have been developed to estimate the CNT Young's modulus and the obtained results cover a large range of scale. In this study, we propose an indirect technique for MWCNT carpet Young's modulus measurements by using the nanoindentation technique. Nanoindentation tests are performed on a metallic film deposited on MWCNT. The measured equivalent reduced modulus takes into account the elastic properties of the metallic thin film and those of the MWCNT substrate. Bec et al. model, introduced in 2006, is used to separate elastic properties, and thus determine the MWCNT reduced Young’s modulus which is estimated between 329 and 352GPa. Knowing the indenter mechanical properties, we estimate the Young’s modulus in the 461 to507GPa range.

(Invited) Modification and Analysis of Carbon Based Structures By Metal Nanoparticulate Ions

Our collaborative work to create and soft land ionized gas phase single crystalline metal nanoparticulate ions onto substrates was motivated by Robert Hauge’s wish to produce templates for carbon nanotube carpet growth. Ionwerks created a machine to do this but, as is often the case, funding was found first for alternative applications. One such has been low energy (500 eV) injection of 8 nm silver nanoparticulate ions (AgNP-) into the near surface of bio-polymers. A uniform layer (70 e15 Ag atoms/cm2) of these implanted particles serve to assist the laser desorption of intact biomolecules from a brain tissue sample into the gas phase. Some of these desorbed molecules are ionized and can be transported into a mass spectrometer and uniquely identified by their exact mass to charge (m/z). By scanning a 50 micron focused laser across the surface of an AgNP implanted rat brain tissue sections, a complete mass spectrum can be acquired at each of several hundred thousand laser locations. Images of specific biomolecules can be derived from these spectra. Putative molecular biomarkers can then be identified by inter-comparing the numerous molecular images from each animal grouping within an animal study. Images from the same brain levels between injured (or diseased) and uninjured rats define histological micro domains in which elevated or decreased molecular ion intensities correlate with other measures of injury/disease state severity. Imaging of these biomarker ions is becoming useful in preclinical screening of drug candidates and should ultimately enter clinical settings. The AgNP enhanced mass spectral imaging has been also applied to the surface analysis of synthetic polymers, fullerenes, and nanotubes. A third application uses 30 keV, 15 nm AgNP ion impacts to form otherwise unattainable controlled nano-sized holes in graphene—especially “rebar” graphene. Alternatively, low energy soft landing at lower energy can form nanostructures upon the graphene which have implications for device formation. However, before departure, Bob made it clear that we needed to get back to carpet growth and other ideas which he outlined in extensive and explicit discussions—mostly at outdoor cafes and coffee shops. His dictates and imprimatur remain.

Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

Here we show that a versatile binary catalyst solution of Fe3O4/AlOx nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlOx nanoclusters over Fe3O4 crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg-1), high-power density capabilities (∼20,500 W kg-1 at 29 Wh kg-1), and a large operating voltage window (4.3 to 0.01 V).

Catalytic CVD growth of millimeter-tall single-wall carbon nanotube carpets using industrial gaseous waste as a feedstock

A gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) was utilized as an efficient feedstock for growth of high-quality, well-aligned single-wall carbon nanotube (SWCNT) carpets of millimeter-scale heights on Fe and (sub) millimeter-scale heights on Co catalysts via chemical vapor deposition (CVD). Although the SWCNT carpets were grown over a wide temperature range (between 650 and 850 °C), growth conducted at optimal temperatures for Co (850 °C) and Fe (750 °C) yielded predominantly SWCNTs that were straight and clean, with sidewalls largely free of amorphous carbon. Growth on Fe is characterized by a relatively high growth rate (∼50 μm/min) and long catalyst lifetime (>90 min), with the catalyst showing no decay of activity, while growth on a Co catalyst shows a lifetime of ∼60 min, with a slower growth rate of ∼7 μm/min. The resulting area densities of SWCNT carpets grown on Fe and Co, determined by the weight-gain method, were 1.0 × 1012 and 6.0 × 1012 cm−2, respectively — among the highest achieved for SWCNT carpets on standard catalysts. Unlike SWCNT carpet growth involving conventional feedstocks, growth rate and density of SWCNTs on Fe are less sensitive to the FTS-GP fraction and thus allow for relatively easy optimization and scale-up.