Non-contact Mode Research Articles

Circulatory leukotriene changes during bone healing following osteotomies prepared with Er:YAG laser and piezosurgery: an animal study

Among high-energy lasers, the short-pulsed infrared erbium-doped yttrium aluminium garnet (Er:YAG) laser has shown the best potential for precise cutting and rapid osseous healing. The objective of the present study was to analyse the healing of the bone tissue treated with short-pulsed infrared erbium-doped yttrium aluminium garnet laser in contact and non-contact mode and piezosurgery in relation to the circulatory leukotriene B4 and cysteinyl leukotrienes. Twenty-four 10-week-old adult male Wistar rats were used. Three osteotomies on the medial part of the tibia were performed on each animal: one on the right tibia and two ones on the left tibia. After surgery, six animals were immediately euthanized and the others were euthanized after 1, 2 and 3 weeks. The bone healing after osteotomy was analysed by a laser-based profilometry. After euthanasia, blood samples were taken from the abdominal aorta and collected for further analysis of the circulatory leukotriene B4 and cysteinyl leukotrienes. A decrease in the osteotomy volume resulted from bone healing during the 3-week period. After the third week, there was almost complete healing of the prepared osteotomies. The circulating levels of both LTB4 and Cys-LTs at 7 and 14 days after osteotomy, were significantly reduced in comparison with the initial levels (p < 0.001 for LTB4 and p < 0.05 for Cys-LTs). On the 21st day after surgical treatment, only the circulating levels of LTB4 were significantly decreased compared to those on day 7 (p < 0.001) and day 14 (p < 0.05). All osteotomies healed through a significant decrease in both examined circulatory LTs.

The effectiveness of home-use photobiomodulation toothbrush for treating dentin hypersensitivity: A pilot study.

Dentin hypersensitivity is a frequent oral condition among patients suffering from gingival recession. Recent studies have suggested that photobiomodulation has the potential to reduce inflammation and relieve pain. The present study aims to assess the effectiveness of a new design of photobiomodulation toothbrush with specific irradiation parameters as a homecare device in treating dentin hypersensitivity and to compare its therapeutic effect with that of fluoride varnish. Thirty patients with gingival recession and dentin hypersensitivity were selected and randomly assigned to three groups of equal size: fluoride varnish, photobiomodulation, and the combination. Dentin pain and hypersensitivity were measured using visual analog scale (VAS) by two distinct tests: the contact test with a periodontal probe and the air blast test on the areas of gingival recession and denuded root; once at baseline and again one month after the initial application of treatments. Laser irradiation was carried out at the wavelength of 660 nm in CW with an output power of 40 mW for 30 seconds per spot (1.2 J per spot, 6 J/cm2 energy density, and 200 mW/cm2 power density), perpendicularly to denuded root surfaces in non-contact mode. A significant reduction in dentin pain and hypersensitivity was observed in all three groups. However, the reduction was significantly greater in the combination group. At-home treatment of dentin hypersensitivity with photobiomodulation toothbrush is a convenient, safe, and effective method for the management of dentin hypersensitivity.

The qPlus sensor, a powerful core for the atomic force microscope.

Atomic force microscopy (AFM) was introduced in 1986 and has since made its way into surface science, nanoscience, chemistry, biology, and material science as an imaging and manipulating tool with a rising number of applications. AFM can be employed in ambient and liquid environments as well as in vacuum and at low and ultralow temperatures. The technique is an offspring of scanning tunneling microscopy (STM), where the tunneling tip of the STM is replaced by using a force sensor with an attached tip. Measuring the tiny chemical forces that act between the tip and the sample is more difficult than measuring the tunneling current in STM. Therefore, even 30 years after the introduction of AFM, progress in instrumentation is substantial. Here, we focus on the core of the AFM, the force sensor with its tip and detection mechanism. Initially, force sensors were mainly micro-machined silicon cantilevers, mainly using optical methods to detect their deflection. The qPlus sensor, originally based on a quartz tuning fork and now custom built from quartz, is self-sensing by utilizing the piezoelectricity of quartz. The qPlus sensor allows us to perform STM and AFM in parallel, and the spatial resolution of its AFM channel has reached the subatomic level, exceeding the resolution of STM. Frequency modulation AFM (FM-AFM), where the frequency of an oscillating cantilever is altered by the gradient of the force that acts between the tip and the sample, has emerged over the years as the method that provides atomic and subatomic spatial resolution as well as force spectroscopy with sub-piconewton sensitivity. FM-AFM is precise; because of all physical observables, time and frequency can be measured by far with the greatest accuracy. By design, FM-AFM clearly separates conservative and dissipative interactions where conservative forces induce a frequency shift and dissipative interactions alter the power needed to maintain a constant oscillation amplitude of the cantilever. As it operates in a noncontact mode, it enables simultaneous AFM and STM measurements. The frequency stability of quartz and the small oscillation amplitudes that are possible with stiff quartz sensors optimize the signal to noise ratio. Here, we discuss the operating principles, the assembly of qPlus sensors, amplifiers, limiting factors, and applications. Applications encompass unprecedented subatomic spatial resolution, the measurement of forces that act in atomic manipulation, imaging and spectroscopy of spin-dependent forces, and atomic resolution of organic molecules, graphite, graphene, and oxides.

Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow

The ability to monitor blood flow is critical to patient recovery and patient outcomes after complex reconstructive surgeries. Clinically available wired implantable monitoring technology requires careful fixation for accurate detection and needs to be removed after use. Here, we report the design of a pressure sensor, made entirely of biodegradable materials and based on fringe-field capacitor technology, for measuring arterial blood flow in both contact and non-contact modes. The sensor is operated wirelessly through inductive coupling, has minimal hysteresis, fast response times, excellent cycling stability, is highly robust, allows for easy mounting and eliminates the need for removal, thus reducing the risk of vessel trauma. We demonstrate the operation of the sensor with a custom-made artificial artery model and in vivo in rats. This technology may be advantageous in real-time post-operative monitoring of blood flow after reconstructive surgery.

Noncontact tip-enhanced Raman spectroscopy for nanomaterials and biomedical applications.

Tip-enhanced Raman spectroscopy (TERS) has been established as one the most efficient analytical techniques for probing vibrational states with nanoscale resolution. While TERS may be a source of unique information about chemical structure and interactions, it has a limited use for materials with rough or sticky surfaces. Development of the TERS approach utilizing a non-contact scanning probe microscopy mode can significantly extend the number of applications. Here we demonstrate a proof of the concept and feasibility of a non-contact TERS approach and test it on various materials. Our experiments show that non-contact TERS can provide 10 nm spatial resolution and a Raman signal enhancement factor of 105, making it very promising for chemical imaging of materials with high aspect ratio surface patterns and biomaterials.

Thermal Analysis and Experimental Validation of a 30 kW 60000 r/min High-Speed Permanent Magnet Motor With Magnetic Bearings

Thermal analysis calculation is an indispensable checking process in the design of the high-speed permanent magnet synchronous machine (HSPMSM) with the active magnetic bearings, due to its high loss density and non-contact support mode. The finite element method (FEM) is applied for visual global temperature distribution. Because the thermal analysis is a complex problem reflected the interaction among the electromagnetic field, temperature field, and fluid field, so it cannot be solved independently, and a multi-physical field simulation based on magneto-thermal-fluid coupled iterative solution is proposed. An electromagnetism (EM) model is established to solve electromagnetic loss and the computational fluid dynamics (CFD) software is used to simulate convective condition, both the results are applied to the thermal analysis of motor. The data interaction is bidirectional and transfers in the form of a field, and the interaction during the EM model, the CFD model, and thermal analysis is fully considered to guarantee high accuracy. Finally, two prototypes of 30-kW 60000 r/min magnetically suspended HSPMSMs have been developed. The experimental results of back-to-back towing test validate the accuracy of the proposed multi-physical field simulation.

Fabrication of Si-based AFM Probe with High Q-factor for Fast Non-Contact Mode Scanning

In non-contact atomic force microscopy, a feedback loop is used to maintain the set-point frequency relative to the force between the specimen and the cantilever. The quality factor of the cantilever affects the sensitivity of feedback loop. Therefore, the fabrication of a high-quality-factor cantilever to improve the scan speed of non-contact atomic force microscopy is highly desirable. Here, we optimized the thickness of the non-contact atomic force microscope’s cantilever to maximize the quality factor with a high resonant frequency. These maximized values reached about 1200 and 530 kHz, respectively. The corresponding scan rate was more than 0.12 mm/s, indicating that the cantilever can be used in high-speed non-contact atomic force microscopy.

Geometric parameters effect of the atomic force microscopy smart piezoelectric cantilever on the different rough surface topography quality by considering the capillary force.

Nowadays, the atomic force microscopy (AFM) is widely used in the nanotechnology as a powerful nano-robot. The surface topography in Nanoscale is by far one of the most important usages of the AFM device. Hence, in this article, the vibration motion of a piezoelectric rectangular cross-section micro-cantilever (MC) which oscillates in the moist environment has been examined based on the Timoshenko beam theory. After extracting the MC governing equations according to Hamilton's principle, the finite element method has been used to discretize the motion equations. The surface topography has been simulated for various roughness forms in the tapping and non-contact modes by considering the effects of the Van der Waals, capillary and contact forces. Also, the experimental results obtained from the glass surface topography have been simulated. The results illustrate that the time delay in higher natural frequencies in the tapping mode is shorter in comparison with the non-contact mode, especially, for the lower natural frequencies. The sensitivity analysis of the natural frequencies, topography depth and time delay have been simulated. Results indicate that the most effective parameter is the MC length. In the first mode, the first section length has the highest effect on the surface topography time delay, also, in the second vibration mode; the most effective parameter on the time delay is the MC tip length based on the simulation results.

Antibody drop based handling with near-superhydrophobic mesh substrates overcomes condensation sticking

Superhydrophobic substrates facilitate low adhesion for biological liquid handling but are hampered by wetting state changes due to condensation. Here, meshed near-superhydrophobic substrates, that are easier to produce than two-tiered architecture substrates, are shown to provide good immunity to wetting state changes while imbuing high positional resistance to roll-off by tilting when tested with 5 and 10 μL volume drops (18° and 13° respectively) of human IgG antibodies in aqueous solution at both room temperature and 4 °C. Pneumatic actuation was applied to elicit horizontal drop movement over the near-SH surface without any fragmentation, wherein higher velocities can be achieved when smaller drops and higher air pressures are used (0.385 m/s at 33 mbar with the 5 μL drop). A non-contact mode of translating a protein drop towards a highly viscous oil-based adjuvant dispensed from a steel tip allowed for both drops to be combined and aspirated back up into the tip such that subsequent repeated cycles of pendant drop formation and upward aspiration allows for effective mixing to achieve a stable emulsion. The findings here advance the development of devices that enable improved antigen-adjuvant preparation by reducing the amount of reagents required and product losses from surface adsorption.

Ho:YAG laser lithotripsy in non-contact mode: optimization of fiber to stone working distance to improve ablation efficiency.

To evaluate how variable working distances between the laser fiber and the stone influence ablation volume. A laser fiber was fixed on a robotic arm perpendicular to an artificial stone. A single laser pulse was triggered at different working distances (0-2.0mm in 0.2mm increments) between the distal fiber tip and the stone. To achieve a measurable impact, pulse energy was set to 2 and 3J, with either short or long pulse duration. Ablation volume was calculated with an optical microscope. Experiments were repeated five times for each setting. Highest ablation volume was observed with a long pulse of 3J at a working distance of 0.4mm between the laser fiber and the stone surface (p value<0.05). At 2J, the highest ablation volume was noticed with a short pulse in contact mode. However, ablation volume of the latter was not significantly greater than with a long pulse of 2J at a working distance of 0.4mm (p value>0.05). Compared to lithotripsy in contact mode, triggering a single long pulse at 0.4mm increased ablation volume by 81% (p value=0.016) at 2J and by 89% (p value=0.034) at 3 J. For Ho:YAG laser lithotripsy, ablation volume may be higher in non-contact mode using long pulses, rather than in direct contact to the stone. Findings of the current study support the need of further studies of lithotripsy in non-contact mode.

Evaluation of Topical Medications, Lavage Solutions, and Laser Therapy for Treating Open Wounds Induced in Blue-fronted Amazon Parrots, Amazona Aestiva

This study aimed to evaluate topical medications, lavage solutions and laser therapy for treating open clean wounds induced in captive blue-fronted Amazon parrots. Twenty-four blue-fronted Amazon parrots (Amazona aestiva) were divided into 6 groups according to the wound treatment: Group DEX—dexpanthenol 5% ointment; Group RIC—ointment of Ricinus communis oil; Group CHL—chlorhexidine digluconate solution 1%; Group SSS—0.9% sterile saline solution; Group LLL—low-level laser therapy and Group CON—no treatment, control. Four full-thickness wounds were induced in the front part of the chest area with the aid of an 8-mm punch. In each parrot, the 4 wounds received the same treatment, every 48 hours until healing, according to the group. In all groups, on postoperative days 5, 14 and 21, biopsies were taken for histological examination. One of the 4 wounds was not submitted to biopsy but rather was used for wound size measurements. Group CON presented the longest healing time and differed statistically from the other groups. Excluding Group CON, groups CHL and SSS showed no significant difference. Microscopically, groups DEX and CHL showed higher fibroplasia and epithelialization compared to the other groups on day 21. In conclusion, the best results were achieved macroscopically through lavage solutions, chlorhexidine digluconate solution or sterile saline solution; however, chlorhexidine digluconate was superior microscopically. The laser therapy and dexpanthenol ointment showed intermediate results, whereas the Ricinus communis oil showed the worst results. It is unclear the exact amount of energy received from the tissue since laser was administered in non-contact mode, and further studies at different laser settings are warranted.

3DAirSig: A Framework for Enabling In-Air Signatures Using a Multi-Modal Depth Sensor.

In-air signature is a new modality which is essential for user authentication and access control in noncontact mode and has been actively studied in recent years. However, it has been treated as a conventional online signature, which is essentially a 2D spatial representation. Notably, this modality bears a lot more potential due to an important hidden depth feature. Existing methods for in-air signature verification neither capture this unique depth feature explicitly nor fully explore its potential in verification. Moreover, these methods are based on heuristic approaches for fingertip or hand palm center detection, which are not feasible in practice. Inspired by the great progress in deep-learning-based hand pose estimation, we propose a real-time in-air signature acquisition method which estimates hand joint positions in 3D using a single depth image. The predicted 3D position of fingertip is recorded for each frame. We present four different implementations of a verification module, which are based on the extracted depth and spatial features. An ablation study was performed to explore the impact of the depth feature in particular. For matching, we employed the most commonly used multidimensional dynamic time warping (MD-DTW) algorithm. We created a new database which contains 600 signatures recorded from 15 different subjects. Extensive evaluations were performed on our database. Our method, called 3DAirSig, achieved an equal error rate (EER) of %. Experiments showed that depth itself is an important feature, which is sufficient for in-air signature verification.

Strategies and progress on improving robustness and reliability of triboelectric nanogenerators

Triboelectric nanogenerator (TENG) is a novel technology converting mechanical energy into electricity and has shown great potential in coping with energy and environmental crisis, and driving emerging electronics. The robustness and reliability represent the ability of TENGs to conduct long-term, stable, and reliable operation, and are considered as the precondition for realizing the extensive and large-scale application of this device in realistic environment. However, the robustness and reliability of TENGs are being severely challenged by frequent, direct and long-term mechanical impacts as well as negative environmental factors during the operation of device. Therefore, how to improve the robustness and reliablity of TENGs is an important issue that urgently need to be addressed. In this article, we review five types of feasible strategies, including noncontact mode, rolling structural, liquid-solid contact, self-recovery and encapsulated TENGs, for the enhancement of robustness and reliability. Some representative examples and their merits are highlighted and demonstrated. The contribution, availability, and challenges toward each strategy are discussed.

Effect of Er,Cr:YSGG on bond strength and microleakage of dentin bonded to resin composite with different distance and irradiation time.

To explore the surface modification of dentin using Er,Cr:YSGG phototherapy and bonding system on the shear bond strength and microleakage scores at two different distances and times of laser irradiation. Ninety disease-free third molars were collected for the experiment. The four laser groups were divided on the basis of non-contact mode distance and time of irradiation: Group-I: Distance of 1 mm with duration of 60 s; Group-II: Distance of 1 mm with duration of 120 s; Group-III: Distance of 2 mm with duration of 60 s and; Group-IV: Distance of 2 mm with duration of 120 s. The surface for control group (Group-EB: Etch & bond group) was treated with etch and rinse bonding regime. Specimens from all the groups were assessed for shear bond strength and microleakage scores. Samples from all groups were immersed in 2% methylene blue for 24 h and assessed under a digital microscope for microleakage. The lowest bond strength and microleakage was observed in the control group EB. The maximum bond strength score was observed in Group-IV with mean scores 23.41 ± 1.83, while the maximum microleakage scores were observed in Group-II and Group-IV with mean scores 1.0 ± 0.36 and 1.0 ± 0.11, respectively. The lowest bond strength and microleakage among laser groups was observed in Group-II and Group-III, respectively. However, specimens in laser groups showed comparable bond strength and microleakge scores (p > 0.05). For bond strength and microleakage values, analysis of variance showed significant difference among the study groups (p < 0.001). Using Tukey post hoc test, bond strength and microleakage of laser groups showed statistically significant values than EB group. Use of phototherapy using Er,Cr:YSGG for dentin surface treatment has the potential for clinical application in comparison to conventional conditioning technique. Increasing the distance of laser application and time of irradiation has significant effect on the shear bond strength and microleakage scores of dentin bonded to resin composite. However, further in-vitro analysis should be undertaken in order to prove such findings.

In vitro effect of diode laser against biofilm of Aggregatibacter actinomycetemcomitans.

Objective:The main objective is to investigate the antibacterial effect of diode laser against Aggregatibacter actinomycetemcomitans biofilm.Materials and Methods:Biofilms of A. actinomycetemcomitans plus Streptococcus sanguinis grown on bovine root surfaces were treated with an 810-nm diode laser using a noncontact pulsed mode with a pulse interval and pulse length of 20 ms. Four protocols, that is, one episode of 1.5 or 2.5 W for 30 s and three episodes of 1.5 or 2.5 W for 30 s were tested. No treatment and 0.2% chlorhexidine treatment served as negative and positive controls, respectively. Viable bacterial number was determined by colony counting.Results:Treatment with chlorhexidine and all laser protocols except that using single episode of 1.5 W reduced the number of A. actinomycetemcomitans in either single-species or dual-species biofilm compared to negative control. A higher percentage of A. actinomycetemcomitans reduction was demonstrated after increasing the power output or repeating the irradiation.Conclusions:The laser protocols used in this study could reduce the number of viable bacteria but not eradicate A. actinomycetemcomitans biofilm.

Accurate placement of single nanoparticles on opaque conductive structures

Single quantum emitters coupled to different plasmonic and photonic structures are key elements for integrated quantum technologies. In order to fully exploit these elements, e.g., for quantum enhanced sensors or quantum repeaters, a reliable fabrication method as enabling technology is crucial. In this work, we present a method that allows for positioning of individual nanocrystals containing single quantum light sources on non-transparent conductive samples with sub-micrometer precision. We induce long-range electrostatic forces between an atomic force microscope tip, which carries a nanoparticle, and the target surface. This allows for mapping of the target area in the non-contact mode. Then, the placement site can be identified with high accuracy without any tip approach, eliminating the risk of a particle loss. We demonstrate the strength of the method by transferring a diamond nanocrystal containing a single nitrogen-vacancy defect to the center of a micrometer-sized silver bullseye antenna with nanometer resolution. Our approach provides a simple and reliable assembling technology for positioning single nano-objects on opaque substrates with high reproducibility and precision.

Effect of three types of piezoelectric cantilever on the topography quality in the vicinity of rough surface in a fluid ambient

• Advanced mathematical modeling for different types of piezoelectric micro cantilever. • Utilizing modified couple stress theory. • Advanced liquid modeling. • Predicting the piezoelectric non uniform micro cantilever vibration behavior in fluid. • Tapping and non-contact topography in liquid. The use of higher vibration modes and different geometries of the atomic force microscopy (AFM) piezoelectric micro cantilever (MC) is affected by the surface topography quality in a liquid medium. Therefore, utilizing an appropriate MC geometry and vibration mode is of a great importance. This paper analyzes the effect of different types of AFM MCs on the surface topography quality in the noncontact and tapping modes in a liquid medium. The modified couple stress theory (MCS) in a liquid based on the Timoshenko beam theory is used in order to enhance the accuracy of MC dynamic modeling. In addition, the differential quadrature (DQ) method has been used to discrete the equations. Identification of environmental forces helps to measure the accurate MC vibration amplitude. Investigating the effect of geometric and force parameters on the MC vibration behavior leads to understanding the system to design it properly in a liquid medium. Based on the advanced dynamic modeling, the best MC geometry for the specific surface roughness has been determined in the liquid for the surface topography. Also, due to oscillating the MC near the sample surface, the effect of interaction forces between the sample surface and the MC, including van der Waals, contact and squeeze forces is analyzed in a liquid medium in addition to the hydrodynamic forces. Furthermore, due to the reduction of the MC amplitude caused by the squeeze force; the MC is angled in proportion to the horizontal surface.

VS02.01: FLEXIBLE ENDOSCOPIC CRICOPHARYNGEAL MYOTOMY WITH THULIUM LASER

Abstract Description Flexible endoscopic treatment of Zenker's diverticulum is feasible, but electrocautery and CO2 laser technology carry the risk of collateral thermal injury. Thulium laser septum incision may overcome this limitation. We describe for the first time the use of thulium laser through flexible endoscopy in a small cohort of patients with Zenker diverticulum. Methods Thulium laser septum division was performed via flexible endoscopy under general anesthesia in 11 consecutive symptomatic patients with primary or recurrent Zenker diverticulum. Primary study aims were feasibility and safety of the procedure. To improve exposure and stabilize the septum during the procedure, either a transparent cap or a bivalve soft overtube were used. The laser system used was Opera® (Quanta System SpA, Varese, Italy), emitting a 1.9 μm Thulium wavelength radiation. A continuous laser configuration and an emission power of 5 to 16 W were chosen to allow incision of the mucosa and cricopharyngeal myotomy. Using 272 and 365 μm optical fibres in a non-contact mode, laser incision was performed in the midline of the septum until cricopharyngeal muscle fibers were encountered and a V-shaped myotomy was completed under visual control. Results Between May and January 2018, 11 consecutive patients were treated. Four patients presented with recurrent symptomatic diverticulum after previous transoral septum stapling or endoscopic myotomy. Median dysphagia and regurgitation scores were 4.1 ± 0.7 and 3.3 ± 0.8 respectively. Complete division of the septum was achieved in all patients. There was no bleeding nor need of adjunctive electrocautery devices to complete the procedure. The post-operative course was uneventful in all patients; the chest film and gastrographin swallow study on post-operative day one were negative for pneumomediastinum or leaks. All patients were discharged within 48 hours on a soft diet. At the 2-month follow-up visit, all patients were satisfied with the procedure with a post-operative dysphagia score of 2.0 ± 0.6 and a regurgitation score of 1.5 ± 0.4. Conclusions Division of Zenker's septum with Thulium laser is feasible and safe through flexible endoscopy. Longer term follow-up is required to establish effectiveness and reproducibility of this novel procedure. Disclosure All authors have declared no conflicts of interest.

Triboelectric–Thermoelectric Hybrid Nanogenerator for Harvesting Energy from Ambient Environments

AbstractRecently developed triboelectric nanogenerators (TENG) with advantages of a low fabrication cost, high output voltage, and high energy conversion efficiency have shown potential applications in harvesting ambient environment energy. However, the heat energy produced and wasted during the triboelectric energy generation process limits the output of TENG. One approach is to design TENG based on a noncontact mode to minimize the energy loss. The other approach is to scavenge the lost energy with a supplementary nanogenerator. In this work, triboelectric–thermoelectric hybrid nanogenerator (TTENG) is fabricated to harvest the energy from ambient environment and the thermal energy from the temperature difference induced by r‐TENG friction. At a rotation rate of 500 rpm, r‐TENG can produce a constant open‐circuit voltage (Voc) of 200 V and a short‐circuit current (Isc) of 0.06 mA. The thermoelectric nanogenerator (TMENG) with a size of 16 cm2 can produce a Voc of 0.2 V and an Isc of 20 mA. The experimental results show that the TTENG is a promising method to harvest the ambient mechanical energy.

Size investigation of silicon nanoclusters deposited on HOPG using noncontact atomic force microscopy

The sizes of silicon nanoparticles produced using two different novel methods are investigated in this report. The method of production used to generate silicon oxide nanoparticles was achieved via gas aggregation codeposition with water on a cold target, and also via a liquid jet method. The nanoparticles were drop-cast on a highly oriented pyrolytic graphite (HOPG) substrate and assessed using ultrahigh vacuum atomic force microscopy (AFM). Noncontact constant force mode was used in the AFM investigations. The silicon nanoparticles produced using the gas aggregation and water codeposition method were found to be smaller than 2 nm. A degree of deviation in the measured sizes of the silicon nanoparticles in different layers was detected. The size deviation was attributed to surface-nanoparticle, surface-tip, and nanoparticle-tip interactions. Silicon nanoparticles produced in alcohol using the liquid jet method were also found to be smaller than 2 nm. The solvent used for the silicon nanoparticles was varied in our investigations. When water was used as a solvent, a size deviation for silicon nanoparticles in different layers was also observed.