Aggregation Of Carbon Nanotubes Research Articles

Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed

Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (dp = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidity with gas velocity. A possible mechanism of aggregates formation was proposed based on the variations of aggregates properties with gas velocity. The obtained Heywood diameters of aggregates have been firstly correlated with the experimental parameter.

Polymer nanocomposites: Insights on rheology, percolation and molecular mobility

The integration of carbon nanotubes (CNTs) into a polymer matrix strongly affects the rheological behavior that in turn may hamper the overall performance of the resulting composite. Research in this topic has focused on bulk rheological properties, while here we employ NMR diffusion experiments to explore the mobility (diffusivity) of epoxy molecules when loaded with CNTs. Rheology and light microscopy indicate percolation of CNT aggregates. Those aggregates cage a substantial amount of epoxy molecules while small angle X-ray scattering indicates some rearrangement of epoxy molecules in the vicinity of the nanotubes. NMR diffusion experiments distinguish between the slow diffusion of the caged molecules and that of the free ones, and relate the fraction of the former to the macroscopic system viscosity. The demonstrated surface-induced slowing-down of diffusion is attributed to strong intermolecular π-π interactions among the epoxy molecules, and between them and the CNT surface. These findings demonstrate the utility of NMR diffusion experiments as an additional method applied to nanocomposites.

Hierarchical core-sheath polypyrrole@carbon nanotube/bacterial cellulose macrofibers with high electrochemical performance for all-solid-state supercapacitors

Fiber-based hybrid electrodes composed of carbon nanotube (CNT) and pseudocapacitance materials have gained great attention for wearable energy storage devices. However, it is still a challenge to obtain high capacitance fiber-based supercapacitor (FSC) with structurally optimized hybrid electrode. Herein, a flexible FSC with hierarchical core-sheath and porous structure is elaborately designed by self-assembly of multiple nanoscale polypyrrole@CNT/bacterial cellulose electrodes. The bacterial cellulose (BC) in the FSC not only efficiently prevent the aggregation of CNTs and significantly improve the wettability of supercapacitor, but also act as electrolyte nano-reservoirs, which can accelerate the diffusion of electrolyte ions and improve the electrochemical performance. The inner hierarchical core-sheath and porous structures significantly increase the specific surface area of the electrode and facilitate the ion transport resulting in considerably enhanced electrochemical properties. The assembled all-solid-state FSC exhibits high energy density of 6.8 mWh/cm3 (8.3 Wh/kg) at power density of 38.6 mW/cm3 (47.3 W/kg), power density of 391.7 mW/cm3 (454.5 W/kg) at energy density of 3.6 mWh/cm3 (4.2 Wh/kg), excellent cycling retention ability and bending ability. This high-performance FSC with well-designed structure fabricated by industrially viable wet-spinning technology, possessing great potential as the energy and power in various portable, miniaturized, and wearable electronic devices.

Carbon nanotube multilayered nanocomposites as multifunctional substrates for actuating neuronal differentiation and functions of neural stem cells

Carbon nanotubes (CNTs) have shown potential applications in neuroscience as growth substrates owing to their numerous unique properties. However, a key concern in the fabrication of homogeneous composites is the serious aggregation of CNTs during incorporation into the biomaterial matrix. Moreover, the regulation mechanism of CNT-based substrates on neural differentiation remains unclear. Here, a novel strategy was introduced for the construction of CNT nanocomposites via layer-by-layer assembly of negatively charged multi-walled CNTs and positively charged poly(dimethyldiallylammonium chloride). Results demonstrated that the CNT-multilayered nanocomposites provided a potent regulatory signal over neural stem cells (NSCs), including cell adhesion, viability, differentiation, neurite outgrowth, and electrophysiological maturation of NSC-derived neurons. Importantly, the dynamic molecular mechanisms in the NSC differentiation involved the integrin-mediated interactions between NSCs and CNT multilayers, thereby activating focal adhesion kinase, subsequently triggering downstream signaling events to regulate neuronal differentiation and synapse formation. This study provided insights for future applications of CNT-multilayered nanomaterials in neural fields as potent modulators of stem cell behavior.

Synthesis, characterization, and interactions of single-walled carbon nanotubes modified with doxorubicin with Langmuir\u2013Blodgett biomimetic membranes

The synthesis, characterization, and the influence of single-walled carbon nanotubes (SWCNTs) modified with an anticancer drug doxorubicin (DOx) on the properties of model biological membrane as well as the comparison of the two modes of modification has been presented. The drug was covalently attached to the nanotubes either preferentially on the sides or at the ends of the nanotubes by the formation of hydrazone bond. The efficiency of the modification was proved by the results of FTIR, Raman, and thermogravimetric analysis. In order to characterize the influence of SWCNT-DOx conjugates on model biological membranes, Langmuir technique has been employed. The mixed monolayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) and SWCNT-DOx with different weight ratio have been prepared. It has been shown that changes in the isotherm characteristics depend on the SWCNTs content. While smaller amounts of SWCNTs do not exert significant differences, the introduction of the prevailing content of the nanotubes increases area per molecule and decreases the maximum value of compression modulus, leading to more fluid monolayer. However, upon increasing the surface pressure, the aggregation of carbon nanotubes within the thiolipid matrix has been observed. Mixed layers of DPPTE/SWCNT-DOx were also transferred onto gold electrodes by means of LB method. Cyclic voltammetry showed that SWCNT-DOx conjugates remain adsorbed at the electrode surface and are stable in time. Additionally, higher values of peak current and DOx surface concentration obtained for side modification prove that side modification allows for more efficient conjugation of the drug to carbon nanotubes.Graphical abstractᅟ

(Invited) Variance Spectroscopy Studies of Single-Walled Carbon Nanotube Aggregation

Understanding aggregation in samples of dispersed, well-individualized single-walled carbon nanotubes (SWCNTs) is important for many basic studies and applications. We will describe a study that uses the recently developed technique of variance spectroscopy to monitor aggregation kinetics of SWCNTs in aqueous surfactant dispersions. Unlike other techniques used to investigate colloidal dispersions, variance spectroscopy resolves individual subpopulations in mixed samples based on their distinct fluorescence signatures. Following the addition of NaCl coagulant to unsorted SWCNT dispersions, we monitored changes in the independent particle concentrations of six semiconducting (n,m) species. These data were supplemented by time-resolved measurements of fluorescence intensity, which showed pseudo-first order kinetics that was independent of SWCNT structure and was attributed to quenching by energy transfer to metallic SWCNTs. The decreases in particle concentration directly revealed aggregation. They were found to fit reasonably well to a second-order rate law with some dependence on structure at higher salt concentrations. Finally, covariance analysis was applied to the variance data to monitor correlated spectral fluctuations arising from specific heteroaggregates. Those results showed equivalent associations between different semiconducting SWCNT species during salt-induced aggregation.

Reliability performance of tin–bismuth–silver (Sn57.6Bi0.4Ag) solder joints with different content of carbon nano-tubes (CNTs) or nickel (Ni)-modified CNTs

In this study, the reliability performance of Sn57.6Bi0.4Ag solder joints containing different amounts (wt%) of CNTs and Ni-coated CNTs (Ni–CNTs) has been investigated. Thermal shock testing was used, as a means of harsh environmental stressing. The theory of the reinforcing effects for these two dopants was discussed. The difference of the dopant redistributing process during reflow soldering was also analysed. The formation mechanisms of cracks in the doped solder joints were elucidated through morphological analyses. Ball shear testing results were reported to substantiate the mechanical strength improvements of such joints. The characteristics of the fracture surfaces were analysed to clarify and correlate the changes in the related performance. Sn57.6Bi0.4Ag solder joints containing 0.03 wt% Ni–CNTs have been shown to offer the optimal reliability performance, as evidenced by its highest resistance to thermal shock. Ni coated ones showed a positive effect on the distribution of CNTs. However, solder joints containing excessive dopants of > 0.05 wt% yielded certain undesirable defects in the thermal shock testing, as evidenced by its deterioration in mechanical properties. The relative significance of such defects, e.g. aggregation of CNTs, formation of loose CNT-alloy structural phases and rapid propagation of cracks, varied considerably depending of the type and amount of dopants.

Self-sensing and mechanical performance of CNT/GNP/UHMWPE biocompatible nanocomposites

Ultra-high molecular weight polyethylene (UHMWPE)-based conductive nanocomposites with reduced percolation and tunable piezoresistive behavior were prepared via solution mixing followed by compression molding using carbon nanotubes (CNT) and graphene nanoplatelets (GNP). The effect of varying wt% of GNP with fixed CNT content (0.1 wt%) on the mechanical, electrical, thermal and piezoresistive properties of UHMWPE nanocomposites was evaluated. The combination of CNT and GNP enhanced the dispersion in UHMWPE matrix and lowered the probability of CNT aggregation as GNP acted as a spacer to separate the entanglement of CNT with each other. This has allowed the formation of an effective conductive path between GNP and CNT in UHMWPE matrix. The thermal conductivity, degree of crystallinity and degradation temperature of the nanocomposites increased with increasing GNP content. The elastic modulus and yield strength of the nanocomposites were improved by 37% and 33%, respectively, for 0.1/0.3 wt% of CNT/GNP compared to neat UHMWPE. The electrical conductivity was measured using four-probe method, and the lowest electrical percolation threshold was achieved at 0.1/0.1 wt% of CNT/GNP forming a nearly two-dimensional conductive network (critical value, t = 1.20). Such improvements in mechanical and electrical properties are attributed to the synergistic effect of the two-dimensional GNP and one-dimensional CNT which limits aggregation of CNTs enabling a more efficient conductive network at low wt% of fillers. These hybrid nanocomposites exhibited strong piezoresistive response with sensitivity factor of 6.2, 15.93 and 557.44 in the linear elastic, inelastic I and inelastic II regimes, respectively, for 0.1/0.5 wt% of CNT/GNP. This study demonstrates the fabrication method and the self-sensing performance of CNT/GNP/UHMWPE nanocomposites with improved properties useful for orthopedic implants.

Impact of surfactant and clay platelets on electrokinetic potential and size distribution in carbon nanotubes aqueous suspensions

Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD® (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.% a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.%) and concentrated (Cs > CsCMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.

Bending analysis of agglomerated carbon nanotube-reinforced beam resting on two parameters modified Vlasov model foundation

The present work deals with bending behavior of nanocomposite beam resting on two parameters modified Vlasov model foundation (MVMF), with consideration of agglomeration and distribution of carbon nanotubes (CNTs) in beam matrix. Equivalent fiber based on Eshelby–Mori–Tanaka approach is employed to determine influence of CNTs aggregation on elastic properties of CNT-reinforced beam. The governing equations are deduced using the principle of minimum potential energy under assumption of the Euler–Bernoulli beam theory. The MVMF required the estimation of γ parameter; to this purpose, unique iterative technique based on variational principles is utilized to compute value of the γ and subsequently fourth-order differential equation is solved analytically. Eventually, the transverse displacements and bending stresses are obtained and compared for different agglomeration parameters, various boundary conditions simultaneously and variant elastic foundation without requirement to instate values for foundation parameters.

Effect of functionalized process and CNTs aggregation on fracture mechanism and mechanical properties of polymer nanocomposite

There is no doubt about the importance of the mechanical properties of polymer nanocomposite reinforced by carbon nanotubes (CNTs) in terms of the exclusive characteristics of both polymer and CNTs. The mechanical performance of carbon nanotubes/polymer nanocomposite (CPNC) depends on several uncertainties such as CNTs’ structural defects and covalent bonds created during functionalized process, CNTs’ distribution, curvature, waviness, aggregation, and polymer net properties. To cover all of the mentioned effective parameters, a multiscale method is defined in which CNTs’ structure and interfacial phase are studied in a nanoscale model and CNTs’ distribution, curvature, and aggregation are studied in a microscale model. According to the neat polymer's properties, both increase and decrease in CNTPN's strength are possible by variations in CNTs curvature, waviness, distribution, and aggregation. Moreover, in CNTs’ functionalization process, CNTPN's ultimate strength and material brittleness are increased and decreased, respectively. But, Young's modulus of nanocomposite is decreased according to the presence of CNT's structural defects created during the functionalization process. Additionally, the improving effect of functionalization process is significantly decreased by increasing the curvature of CNTs, and the functionalized CNTs polymer nanocomposite's (FCPNC) ultimate strength is close to the intact CNTs polymer nanocomposite's (ICPNC's) strength properties. CNTs’ aggregation has also an adverse effect on Young's modulus and changes the fracture mechanism.

About the relevance of waviness, agglomeration, and strain on the electrical behavior of polymer composites filled with carbon nanotubes evaluated by a Monte-Carlo simulation

In several technological applications, carbon nanotubes (CNT) are added to a polymer matrix in order to develop electrically conductive composite materials upon percolation of the CNT network. This percolation state depends on several parameters such as particle characteristics, degree of dispersion, and filler orientation. For instance, CNT aggregation is currently avoided because it is thought that it will have a negative effect on the electrical behavior despite some experimental evidence showing the contrary. In this study, the effect of CNT waviness, degree of agglomeration, and external strain, on the electrical percolation of polymer composites is studied by a three dimensional Monte-Carlo simulation. The simulation shows that the percolation threshold of CNT depends on the particle waviness, with rigid particles displaying the lowest values. Regarding the effect of CNT dispersion, our numerical results confirm that low levels of agglomeration reduce the percolation threshold of the composite. However, the threshold is shifted to larger values at high agglomeration states because of the appearance of isolated areas of high CNT concentrations. These results imply, therefore, an optimum of agglomeration that further depends on the waviness and concentration of CNT. Significantly, CNT agglomeration can further explain the broad percolation transition found in these systems. When an external strain is applied to the composites, the percolation concentration shifts to higher values because CNT alignment increases the inter-particle distances. The strain sensitivity of the composites is affected by the percolation state of CNT showing a maximum value at certain filler concentration. These results open up the discussion about the relevance in polymer composites of the dispersion state of CNT and filler flexibility towards electrically conductive composites.

Фрактальная модель переноса механического напряжения в нанокомпозитах полиуретан / углеродные нанотрубки

In this communication effect of structure of nanofiller (carbon nanotubes) on transfer of applied to sample mechanical stress from polymer matrix to nanofiller was considered on exam-ple of nanocomposites polyurethane/carbon nanotubes. It was postulated that carbon nanotubes are formed in polymer matrix of nanocomposite ring-like formations, which are structural ana-logue of macromolecular coils of branched polymer chains and specific type of aggregation for carbon nanotubes in virtue of their low transverse stiffness and high anisotropy degree. Indicated formations structure can be characterized most precisely and physically strictly by its fractal di-mension. It has been found, that transfer of mechanical stress in nanocomposite deteriorates at enhancement of indicated fractal dimension and at reaching of this dimension of value of pa-rameter for surrounding Euclidean space nanofiller losses ability to reinfore matrix polymer ow-ing to absence of mechanical stress transfer between its components. Thickness of interfacial layer in polymer nanocomposite is structural characteristic, defining efficiency of applied me-chanical stress transfer. The using of alternative methodics for determination of radius of ring-like formations of carbon nanotubes shows enhancement of their number per one indicated formation at increasing of nanofiller contents. This effect results also to enhancement of fractal dimension of ring-like formation of carbon nanotubes. By analogy with “permeable” macromolecular coils of polymer chains this type of aggregation of carbon nanotubes is realized at fractal dimension of their for-mations of 1.50 and more. Indicated analogue application allows to estimate the Flory-Huggins interaction parameter, which proves to be higher essentially in comparison with polymer macro-molecules.

Porous carbon nanotube/graphene composites for high-performance supercapacitors

Carbon nanotubes (CNTs) are an effective spacer to prevent the re-stacking of graphene layers. However, the aggregation of CNTs always reduces the specific surface area of resulting CNT/graphene composites. Meanwhile, different pores always have different contributions to the specific capacitance. In this study, CNT/graphene composites with different porous structures are synthesized by co-reduction of oxidized CNTs and graphene oxide with different mixing ratios. With an optimized CNT content of 20%, the CNT/graphene composite shows 206 F g−1 in 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. It is found that pores larger than twice the size of electrolyte ions can make greater contributions to the specific capacitance.

Directed aggregation of carbon nanotube on curved surfaces by polymer induced depletion attraction

In this study, we show that by chemically grafting macromolecule, polyethylene glycol (PEG), onto CNTs, PEG-CNTs become dispersible in an aqueous solution with tunable depletion interactions with each other. The aggregation of the PEG-CNTs can be controlled by adding PEG polymers into the solution. PEG-CNTs not only aggregate with each other but also tend to aggregate on curved surfaces. Due to this property, we show that PEG-CNTs can be directed to aggregate on particles and patterned surfaces. Depletion interaction induced aggregation of PEG-CNTs may provide a method to place PEG-CNTs on a specific position for different applications ranging from biomedical to industrial usages.

Effect of degassing on the aggregation of carbon nanotubes dispersed in water

Dynamic light scattering (DLS) along with centrifugation and shaking tests reveal that dissolved gases can significantly affect the aggregation behavior of carbon nanotubes (CNTs) dispersed in water. The CNTs in non-degassed samples form loose, stable networks having the DLS result reminiscent of semidilute polymer solutions, whereas the CNTs in degassed samples aggregate to form Brownian colloids that sediment quickly. Interestingly, the CNTs dispersed in acetone, with or without degassing, also behave like semidilute polymers in DLS experiments. We propose a surface nanobubble-assisted mechanism to explain the observed aggregation behaviors. Our work signifies that dissolved gases may play an important role in determining hydrophobicity and biomolecular functions in aqueous environments.

Novel Polymer Wrapping of Single-Walled Carbon Nanotube By Radical Polymerization

Functionalization of carbon nanotubes (CNTs) is of importance for fundamental studies and the applications of CNTs since as-produced CNTs form aggregated/bundle structures and their dispersion in solution requires CNT functionalization. Especially, biological applications, one of the most promising applications for CNTs, strongly require a stable functionalization since the aggregation of CNTs has the risk of toxicity in vivo. As a functionalization method, chemical functionalization based on the covalent bond provides a stable modification of the CNT surfaces. However, the introduction of the structural defects decreases the unique CNT features such as large area-hydrophobicity surfaces useful for hydrophobic drug loading on the surfaces. On the other hand, physical (noncovalent) modification based on the physical adsorption of the functional molecules onto the CNT surfaces is able to retain the structure and intrinsic properties of the CNTs. For CNT biological applications, we need to recognize that the physical adsorption of small molecules is a dynamic process and the exchange of the molecules on the CNTs with the molecules in the bulk solution is always occurring, which causes the removal of the adsorbed molecules from the CNT surfaces inside the body. The use of a polymeric dispersant dramatically improves the stability of the CNTs through a multipoint physical adsorption, but it has been revealed that the wrapped polymer is unwrapped when a large number of molecules having a strong affinity with the CNTs are added. Indeed, Cherukuri et al. reported that the injection of polymer-wrapped Single-walled carbon nanotubes (SWNTs) into blood sera resulted in rapid displacement by endogenous proteins since some proteins very strongly adsorb onto the SWNT surface. Such a risk of aggregation and the replacement in vivo requires a new functionalization method to enhance the dispersion stability.In 2003, Taton et al. reported a pioneering study to stabilize polymer-wrapped SWNTs based on the cross-linking of the polymers around the CNTs. Similarly, the cross-linking of surfactant micelles has been studied to improve the stability of the CNT dispersion states. Such cross-linking strategies provide a promising approach to achieve a highly stable and non-destructive CNT coating because the wrapping layers are stabilized based on the covalent bonding of polymers around the CNT surfaces. However, this approach has only been applicable to molecules that are able to disperse the CNTs, which prevents the versatility of the concept.Here, we demonstrate a new strategy to synthesize a cross-linked polymer network with an ultrathin layer (~nm-size) around the surface of the CNTs using the inner nanospace of a surfactant micelle as the regulated polymerization site. It has been recognized that in the CNT solutions dispersed by surfactant micelles, the CNTs are encapsulated by the surfactant micelles to provide a stable dispersion of the CNTs. Recently, the molecular penetration inside the micelles due to the hydrophobicity of the interior space was reported. Therefore, the monomer or the polymer together with the cross-linker is expected to penetrate inside the interior of the micelles due to the relatively hydrophobic nature of the space and form a cross-linked polymer network around the CNTs. One of great advantages of our strategy is that there is no need for the monomers to disperse the CNTs since the CNT dispersion is carried out by the surfactant micelles, thus a variety of monomers are applicable to the present system.

Mechanical properties and microstructure characterization of well-dispersed carbon nanotubes reinforced copper matrix composites

Copper (Cu) matrix composites reinforced with 0.3, 0.5, 1.0, and 2.0 vol% multi-wall carbon nanotubes (MWCNTs) were processed by ultrasonication and high-energy attritor milling of pure copper powder with carbon nanotubes (CNTs), followed by spark plasma sintering and annealing. Microstructural characterization shows that the CNTs are well-dispersed in Cu-0.5 vol% CNTs composite, and the aggregation of CNTs increases with the increase in the volume fraction of carbon nanotubes. Raman spectroscopy results indicate that there is an increase in the number of defects in the nanotube after milling and sintering of the composite. Mechanical property and strengthening mechanism analysis indicates that the grain size effect, hindering effect of dislocations interacting with the grain boundary, and load transfer effect are the main mechanisms affecting the mechanical properties of composites, and the experimental strength of the composite can be close to 81% of the theoretical strength.

Carbon nanotube release from polymers into a food simulant

The release assessment of multi-walled carbon nanotubes (CNTs) was performed on two types of polymer-CNT nanocomposites: polypropylene (PP) and polyamide 6 (PA6) containing 3 wt% CNT. Nanocomposite films were prepared and then exposed to ethanol as a fatty-food simulant at 40 °C, and the amount of CNT release into ethanol was determined by ultraviolet-visible spectroscopy (UV-Vis) and graphite furnace atomic absorption spectrometry (GFAAS). The CNTs released into ethanol were visualized by transmission electron microscopy (TEM) and verified by Raman spectroscopy. UV-Vis analysis showed a very small amount of CNT release from the nanocomposite films into ethanol over 60 d: maximum CNT concentrations in ethanol were 1.3 mg/L for the PP-CNT film and 1.2 mg/L for the PA6-CNT film. GFAAS results indicated that the amount of CNTs released into ethanol after 12 d was over 20-fold higher than the results obtained by UV-Vis. Overestimation of CNT release by GFAAS suggested aggregation and poor dispersion of CNTs in the solvent. This assumption was verified by TEM images exhibiting the embedded CNTs in the polymer flakes, which could be poorly dispersed in the solvent. In general, CNT release from the nanocomposite films was considered a surface phenomenon, as indicated by detachment of CNT-containing polymer flakes from the film surface.

3D Microstructured Carbon Nanotube Electrodes for Trapping and Recording Electrogenic Cells

Electrogenic cells such as cardiomyocytes and neurons rely mainly on electrical signals for intercellular communication. Microelectrode arrays (MEAs) have been developed for long‐term recording of cell signals and stimulation of electrogenic cells under low‐cell‐stress conditions, providing new insights in the behavior of electrogenic cells and the operation of the brain. To date, MEAs are relying on flat or needle‐shaped electrode surfaces, mainly due to limitations in the lithographic processes. This paper relies on a previously reported elasto‐capillary aggregation process to create 3D carbon nanotube (CNT) MEAs. This study shows that CNTs aggregate in well‐shaped structures of similar size as cardiomyocytes are particularly interesting for MEA applications. This is because i) CNT microwells of the right diameter preferentially trap individual cardiomyocytes, which facilitates single cell recording without the need for clamping cells or signal deconvolution, and ii) once the cells are trapped inside of the CNT wells, this 3D CNT structure is used as an electrode surrounding the cell, which increases the cell–electrode contact area. As a result, this study finds that the recorded output voltages increase significantly (more than 200%). This fabrication process paves the way for future study of complex interactions between electrogenic cells and 3D recording electrodes.