Single Carbon Nanocoil Research Articles

A Light-Driven Carbon Nanocoil Microrobot

Mobile microrobots are of great scientific significance. However, external actuation and control methods are still challenging to conduct. We present a single carbon nanocoil (CNC) microrobot induced by an NIR laser beam, capable of light-driven locomotion and photothermal actuation. This research demonstrates that CNC-based microrobots rolls away from the focal spot when the laser beam is focused near the CNC. The maximum translational distance of a CNC microrobot increases with an increase in laser power, and the direction of motion is guided by controlling the focusing position of NIR. CNC-based microrobots can load and transport multiple cells under NIR light irradiation, resulting from the temperature gradient generated by photothermal conversion, which causes thermophoresis. The hydrophobic surface and unique helical structure of CNCs are beneficial to the underwater drag reduction in CNC microrobots’ motion and the adhesion of cells on CNC microrobots. Therefore, CNC microrobots, as cell vectors driven by a laser beam, may find applications in a wide range of biomedical applications. In addition, the rotation of a CNC powered by a laser beam provides promising prospects for the future of nanomechanical devices using a carbon nanocoil as a micro/nanomotor.

Probing the Thermoelectricity in Single Carbon Nanocoil for the Design of a Nano Thermocouple

Probing the Thermoelectricity in Single Carbon Nanocoil for the Design of a Nano Thermocouple

Humidity response of single carbon nanocoil and its temperature sensor independent of humidity and strain

Carbon nanocoil (CNC) is a quasi-one dimensional material with unique helical morphology, which provides abundant sites for the adsorption of water and other gas molecules. Herein, we investigated the humidity response of CNCs, including the response mechanism and further regulation. We used several methods to modify the physical and chemical structures of CNC, including 1200 °C annealing, HCl, NH3H2O and H2O2 treatments, to regulate its humidity response and analyze response mechanism. We experimentally demonstrated the p-type conduction of CNCs and the donor characteristic of the adsorbed water molecules, which are not affected by treatment methods. It is found that NH3H2O treatment greatly suppresses the humidity response (almost no response) without affecting the temperature response of CNCs, while annealing suppresses the humidity and temperature response of CNCs simultaneously. Due to the abundant vacancies, defects and functional groups in CNCs, NH3H2O treatment introduces non-volatile water molecules into CNCs, which prevent further adsorption of water molecules and inhibit the humidity response of CNCs. By this way, we achieved an independent temperature sensor of CNCs with no response to humidity, which paves the way for the device based on single CNCs that is independent of humidity and strain.

In situ investigation of annealing effect on thermophysical properties of single carbon nanocoil

In reported high-temperature annealing of carbon nanocoils (CNCs), the samples studied before and after annealing are different ones. This significantly hinders annealing effect understanding due to unknown and remarkable sample-to-sample structure difference. Here using the transient electro-thermal technique (TET) and current-induced annealing, we report the first time in situ investigation of annealing effect on the thermophysical properties for the same individual CNC. Our dynamic annealing track uncovers an electrical resistance relation with annealing time as R∼−Rsln(t). The reaction rate (Rs) shows a normal distribution against the annealing power/temperature, proposing that the activation energy for structure reconstruction in CNCs follows a normal distribution. After annealing at 5–35€μA, the average thermal diffusivity (α) and electrical conductivity (σ) of CNCs show respective 50–160% and 100–170% increase. Normative linear relation between α and σ is discovered, which proposes axial-direction parallel structure in CNCs. The nonuniform temperature distribution along the sample during annealing creates different annealing levels and provides a great advantage to study the relation between structure and thermophysical properties. Our micro-scale Raman characterization reveals the nonuniform distribution of grain size along the length direction of CNCs after annealing and finds a rapid grain size increase from 4.0 to 7.8 nm near the sample's middle point. The middle point of the sample has the highest temperature rise (Tc), largest thermal conductivity (κ) increase, and the most dramatic structure improvement. Its κ shows a rapid improvement (8.7-fold maximum change) from 1200 K to 1800 K. A linear relation between κ−1 and Tc is observed and is attributed to the change of grain size during annealing. Using the concept of thermal reffusivity (Θ=1/α), a 1-fold increase of average grain size and a 197 K decrease of Debye temperature of CNCs after annealing are uncovered.

A carbon nanocoil-based flexible tip for a live cell study of mechanotransduction and electro-physiological characteristics.

The responses of living cells to external mechanical and electrical stimulation play important roles in regulating their biological functions and behaviors, and the response mechanisms have attracted great attention. Global stimulation on cells is generally used in traditional methods, but it is insufficient to investigate the mechanism of a dynamic physiological response at the subcellular level. At present, there is still lack of a low-cost and easy-operated method to apply local mechanical force and electrical stimulation on living cells. In this study, an individual carbon nanocoil (CNC) is used as a microscale noninvasive tool for local stimulation on a single cell, and a living cell imaging technology, fluorescence resonance energy transfer (FRET), is adopted to determine the responses of cells. After demonstrating that CNCs have low cytotoxicity to be applied in the biological field, an individual CNC is used as a needle tip to apply local mechanical force on a single osteosarcoma cell, which is transfected with a Src FRET biosensor to explore the mechano-physiological response. A spatially increasing and polarized Src protein activation is observed on the stimulated cell. Moreover, a single CNC is also used as an electrode to exert periodic local electrical stimulation. Osteosarcoma cells transfected with calcium-FRET biosensors show notable spatial-polarized FRET emission ratio distribution, and the FRET ratio shows a recoverable tendency towards the initial state after withdrawing the electrical stimulation. The cell biofunctions and structures are not damaged during the experiment process, which indicates that CNC is a kind of non-invasive and bio-safe tip. The CNC tip is a powerful tool for exploring the mechanotransduction and electro-physiological characteristics of living cells.

The mechanical oscillation of a single carbon nanocoil driven by a focused laser beam

We have determined the mechanical properties of a long single carbon nanocoil (ALS-CNC) interacting with a focused laser beam. The mechanical oscillation properties of ALS-CNC in liquid based on the interaction of a CNC with light have been demonstrated. Considering the viscous force of a liquid, ALS-CNC oscillation does not occur by laser irradiation when ALS-CNC is in air. A CNC switch controlled by laser irradiation was realized. The first section in your paper.

Highly Efficient Near-Infrared Photothermal Conversion of a Single Carbon Nanocoil Indicated by Cell Ejection

Carbon nanocoil (CNC), which has excellent properties of near-infrared (NIR) absorption and photoelectrical response, is considered as a potential NIR sensing and bioengineering material. In this work, a high-speed living cell ejection is realized in a yeast cell solution based on the photothermal conversion induced by a NIR laser irradiation on the surface of a CNC. The cell ejection reveals a thermal convection of solution induced by the laser irradiated CNC and can be used to evaluate the photothermal conversion ability of CNC. The dynamic behavior of the thermal convection behind cell ejection is studied experimentally and analytically. It is found that the initial solution flow velocity of the dynamic process reaches more than 103 μm/s. Approximately, 60% of the laser energy illuminated on the CNC is converted into thermal energy. The unique helical morphology of CNC enables its high NIR photothermal conversion efficiency. The average convective heat transfer coefficient on the contact area between CNC and surrounding water is deduced to be as high as 7.0 × 105 W/(m2·K). These results indicate that CNC has promising potential applications on microfluidics, laser-operated flow cytometers, bioparticle ejection, and micro-/nano-laser-operated heat generators and exchangers.

Optically Actuated Carbon Nanocoils

Optical manipulation on microscale and nanoscale structures opens up new possibilities for assembly and control of microelectromechanical systems and nanoelectromechanical systems. Static optical force induces constant displacement while changing optical force stimulates vibration of a microcantilever/nanocantilever. The vibratory behavior of a single carbon nanocoil cantilever under optical actuation is investigated. A fitting formula to describe the laser-induced vibration characteristics is deduced based on a classical continuum model, by which the resonance frequency of the carbon nanocoil can be determined directly and accurately. This optically actuated vibration method could be widely used in stimulating quasi-1D micro/nanorod-like materials, and has potential applications in micro-/nano-opto-electromechanical systems.

Thermal Diffusivity of a Single Carbon Nanocoil: Uncovering the Correlation with Temperature and Domain Size

The helical geometries and polycrystalline-amorphous structure of carbon nanocoils (CNCs), an exotic class of low-dimensional carbon nanostructures, distinguish them from carbon nanotubes and graphene. These distinct structures result in very different energy transport from that in carbon nanotubes and graphene, leading to important roles in applications as wave absorbers, near-infrared sensors, and nanoelectromechanical sensors. Here we report a systematic study of the thermal diffusivity (α) and conductivity (κ) of CNCs from 290 to 10 K and uncover their property-structure aspects. Our room-temperature α study reveals a correlation between α and the line diameter (d): α = (5.43 × 104 × e-d/37.7 + 9.5) × 10-7 m2/s. Combined with the Raman-based grain size (La) characterization, α and La are correlated as α = [81.2 × (La - 3.32)1.5 + 9.5] × 10-7 m2/s. With temperature decreasing from 290 K to 10 K, α has a 1-1.6-fold increase, and κ shows a peak around 75 K. To best understand the defect level and polycrystalline-amorphous structure of CNCs, the thermal reffusivity (Θ = α-1) of CNCs is studied and compared with that of graphite and graphene foam from 290 K down to 10 K. Very interestingly, CNC's Θ linearly decreases with decreased temperature, while Θ of graphite and graphene foam have an exponential decrease. The extrapolated 0 K-limit Θ is determined by low-momentum phonon scattering and gives a structure domain size of CNC samples (d = 455, 353, and 334 nm) of 1.28, 2.03 and 3.24 nm. These sizes are coherent with the X-ray diffraction results (3.5 nm) and the Raman spectroscopy study and confirm the correlation among d, La, and α.

Tearing-off method based on single carbon nanocoil for liquid surface tension measurement

A single carbon nanocoil (CNC) is used as a highly sensitive mechanical sensor to measure the surface tension coefficient of deionized water and alcohol in the tearing-off method. The error can be constrained to within 3.8%. Conversely, the elastic spring constant of a CNC can be accurately measured using a liquid, and the error is constrained to within 3.2%. Compared with traditional methods, the CNC is used as a ring and a sensor at the same time, which may simplify the measurement device and reduce error, also all measurements can be performed under a very low liquid dosage owing to the small size of the CNC.

Laser Driven Paraffin Microsphere Transportation on a Single Carbon Nanocoil

Laser driven mass transportation on a single carbon nanocoil (CNC) has been investigated, by regulating the controlling current and the laser focus position. It is found that a paraffin microsphere on a single CNC can be removed by the irradiation of an infrared laser beam on the CNC body near themicrosphere. This phenomenon is explained by a thermal driven forceresulted by a temperature gradient along the CNC around the irradiation spot wherethe laser energy is transformed into thermal energy.

Near-infrared response of a single carbon nanocoil

The near-infrared photoresponse of a single suspended carbon nanocoil (CNC) is investigated. Under the irradiation of a 785 nm laser beam, the photoresponse is generated in the voltage-biased CNC. At a voltage of 50 mV, the ratio of the conductance change to the initial conductance, which is defined as the sensitivity in this paper, can reach 22% and the typical response time is 5 ms. It is found from the changes of photoresponse with pressure and with the laser power that the photoresponse of the CNC is mainly attributed to the bolometric effect. Because of the increase of Joule heating, the sensitivity reduces with the elevation of the bias voltage. However, the responsivity increases with the increase of the bias voltage, which is opposite to the change of the sensitivity. The maximum responsivity of the single CNC IR sensor is 0.22 A W(-1).

Electrically driven light emission from a single suspended carbon nanocoil

Electrically driven thermal radiation spectra from single suspended carbon nanocoils (CNCs) were investigated. The suspended CNC, whose structure is a hybrid between sp2 graphite-like nanocrystallites and sp3 amorphous carbon, shows thermally excited emission peaks superimposed on the blackbody radiation spectrum for wavelengths above 600nm. It is believed that at least four pairs of energy bands exist around the Fermi energy level and the observed emission peaks are attributed to thermally-excited interband electron transitions in the CNC. Photoluminescence measurements for the CNCs show similar emission peaks to the thermally excited emission, which further supports our speculation on the electronic structure of the CNC.

Rapid Dielectrophoresis Assembly of a Single Carbon Nanocoil on AFM Tip Apex

We assembled a single carbon nanocoil (CNC) on the tip apex of an atomic force microscope probe by utilizing dielectrophoresis in isopropyl alcohol (IPA). The total assembly process can be achieved within several seconds at room temperature by using a simple apparatus. Three-dimensional finite element simulations have been conducted to investigate the orientation and position of this assembly. Our experiment agrees well with the simulation. The results indicate that it is essential to filter the CNC/IPA suspension and manipulate the capillary meniscus for a single CNC to be vertically assembled on the tip apex. An inclined-edge electrode has, therefore, been suggested and found effectively confining the CNC/IPA suspension around the probe tip.

Thermal conductivity of a single carbon nanocoil measured by field-emission induced thermal radiation

The spectrum of thermal radiation induced by field emission from a single carbon nanocoil (CNC) is obtained, from which its thermal conductivity is investigated. It is found that the resistivity of the CNC shows an exponential decrease with increasing temperature. The spectrum calculated by the temperature distribution along the CNC coincides with that calculated by the single maximum temperature in the wavelength range below 1250 nm, but shows considerable differences in intensity and peak position for higher wavelengths. Based on this understanding, the thermal conductivity of the CNC is evaluated to be 38 W/m K by a one-dimensional thermal conduction model.