Electrothermal Devices Research Articles

Расчет теплопроводности нефтенасыщенных песчаных грунтов

Nowadays, there are significant heavy high-viscosity oil reserves in the Russian Federation with oil recovery coefficient not higher than 0.25-0.29 even with applying modern and efficient methods of oil fields development. Thermal methods are the most promising out of the existing ways of development, main disadvantage of which is large material costs, leading to the significant rise in the cost of extracted oil. Thus, creating more efficient thermal methods and improving the existing ones, is the task of great importance in oil production.One of the promising trends in enhancing thermal methods of oil recovery is the development of bottomhole electric steam generators. Compared to the traditional methods of thermal-steam formation treatment, which involve steam injection from surface, well electrothermal devices can reduce energy losses and improve the quality of steam injected into the formation. For successful and efficient organization of oil production and rational development of high-viscosity oil fields using well electrothermal equipment, it is necessary to take into account the pattern of heat propagation, both in the reservoir and in the surrounding space, including the top and bottom. One of the main values characterizing this process is the heat conductivity λ of oil-bearing rocks. The article describes composition of typical oil-saturated sand soils, presents studies of heat and mass transfer in oil-saturated soils, reveals the effect of various parameters on the heat conductivity of a heterogeneous system, proposes a method for calculating the heat conductivity of oil-bearing soils by sequential reduction of a multicomponent system to a two-component system and proves the validity of the proposed approach by comparing acquired calculated dependencies and experimental data.

Assembly of carbon nanodots in graphene-based composite for flexible electro-thermal heater with ultrahigh efficiency

A high-efficiency electro-thermal heater requires simultaneously high electrical and thermal conductivities to generate and dissipate Joule heat efficiently. A low input voltage is essential to ensure the heater’s safe applications. However, the low voltage generally leads to low saturated temperature and heating rate and hence a low thermal efficiency. How to reduce the input voltage while maintaining a high electro-thermal efficiency is still a challenge. Herein, a highly electrical and thermal conductive film was constructed using a graphene-based composite which has an internal three-dimensional (3D) conductive network. In the 3D framework, cellulose nanocrystalline (CNC) phase with chiral liquid crystal manner presents in the form of aligned helix between the graphene oxide (GO) layers. Carbon nanodots (CDs) are assembled inside the composite as conductive nanofillers. Subsequent annealing and compression results in the formation of the assembled GO-CNC-CDs film. The carbonized CNC nanorods (CNR) with the helical alignment act as in-plane and through-plane connections of neighboring reduced GO (rGO) nanosheets, forming a conductive network in the composite film. The CDs with ultrafast electrons transfer rates provide additional electrons and phonons transport paths for the composite. As a result, the obtained graphene-based composite film (rGO-CNR-CDs) exhibited a high thermal conductivity of 1,978.6 W·m−1·K−1 and electrical conductivity of 2,053.4 S·cm−1, respectively. The composite film showed an outstanding electro-thermal heating efficiency with the saturated temperature of 315 °C and maximum heating rate of 44.9 °C·s−1 at a very low input voltage of 10 V. The freestanding graphene composite film with the delicate nanostructure design has a great potential to be integrated into electro-thermal devices.

MEMS 열전소자를 이용한 교류실효전압 측정표준

본 논문은 국가측정표준에서 중요한 기여를 하고 있는 MEMS 열전소자에 대해 기술하였다. 교류실효전압은 MEMS 기술로 제작된 PMJCT와 기준 직류전압을 이용하여 정확하게 측정할 수 있으며 이 때문에 MEMS기술로 제작된 PMJTC는 교류실효전압과 직류전압을 연결하는 AC-DC 전달표준으로 사용된다. PMJTC는 교직차로 정의되는 고유 오차를 가지고 있으며 이는 기준 PMJCT와 비교측정을 통해 교정한다. 현재 우리나라는 PMJTC를 이용하여 10 Hz - 1MHz 주파수 대역에서 2 mVSUBrms/SUB 부터 1000 VSUBrms/SUB에 이르는 AC-DC 전달표준을 구현하고 있다.

A novel technique for preventing postoperative pancreatic fistulas after distal pancreatectomy

Introduction: Many techniques have been described for the transection and closure of the pancreatic remnant during distal pancreatectomy, yet the pancreatic fistula rate after distal pancreatectomy remains 15–40%. Herein, we describe a novel technique which has decreased the pancreatic fistula rate at our institution. Methods: A case series was performed evaluating the pancreatic leak rate in patients undergoing distal pancreatectomy. A novel non-closure technique was applied, utilizing an electrothermal bipolar tissue sealer in an “open jaw” technique to transect the pancreas, followed by saline-couple bipolar tissue sealer to coagulate the stump of the pancreatic remnant. Drain amylase was measured one day after initiating patients' diets to detect pancreatic leak. Thirty day follow up was also performed for detection of late pancreatic leaks or formation of fistulae. Results: Six distal pancreatectomies were performed, by a single surgeon, during the study period. Indications included neuroendocrine tumor, adenocarcinoma, IPMN and lymphoepithelial cyst. A laparoscopic approach was utilized in 50%. All but one patient underwent splenectomy. Mean drain amylase one day after initiating a diet was 47 (19 – 91), with no patients exhibiting evidence of leak. At thirty day follow up, all 6 patients remained without signs or symptoms of leak or fistula. Conclusion: A novel technique using electrothermal and saline-coupled bipolar devices resulted in no pancreatic leaks or fistulae in our small series of distal pancreatectomies. Larger series and comparative studies are required to determine the optimal method of pancreatic transection for preventing pancreatic leaks.

Generation of Noble and Refractory Metals Plasma Jets by Electrothermal Discharge for Surface Deposition Applications

Arc-dominated capillary discharges generate high-density plasmas from the ablation of the material of the inner lining sleeve, where ablation is determined by the radiant energy transport in such electrothermal (ET) plasma devices. Properties of sleeve material are an important factor on the generated plasma in ET devices. The 1-D time-dependent NC State University ET plasma code ETFLOW provides simulation of the capillary discharge and predicts the plasma parameters along the capillary axis. Of interest are the plasma parameters at the exit of the capillary which include temperature, pressure, velocity, heat flux and total ablated mass ejected from the source. The experimental discharge current was used in the code, and the plasma parameters at the source exit were calculated. Six materials were tested, namely, titanium, chromium, copper, silver, platinum, and gold. The code results show that the plasma temperature is between 2.4 and 2.57 eV for all tested materials. The lower heat of sublimation of gold and silver leads to increase the total ablated mass, density, electrical conductivity, and the exit pressure combined with reduction of the plasma bulk velocity. The gold has the highest ablated mass while titanium has the lowest values. The total ablated mass of copper material is about 168 mg, which is in a good agreement with previous experimental results.

Closure methods of the appendix stump for complications during laparoscopic appendectomy.

Laparoscopic appendectomy is amongst the most common general surgical procedures performed in the developed world. Arguably, the most critical part of this procedure is effective closure of the appendix stump to prevent catastrophic intra-abdominal complications from a faecal leak into the abdominal cavity. A variety of methods to close the appendix stump are used worldwide; these can be broadly divided into traditional ligatures (such as intracorporeal or extracorporeal ligatures or Roeder loops) and mechanical devices (such as stapling devices, clips, or electrothermal devices). However, the optimal method remains unclear. To compare all surgical techniques now used for appendix stump closure during laparoscopic appendectomy. In June 2017, we searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 6) in the Cochrane Library, MEDLINE Ovid (1946 to 14 June 2017), Embase Ovid (1974 to 14 June 2017), Science Citation Index - Expanded (14 June 2017), China Biological Medicine Database (CBM), the World Health Organization International Trials Registry Platform search portal, ClinicalTrials.gov, Current Controlled Trials, the Chinese Clinical Trials Register, and the EU Clinical Trials Register (all in June 2017). We searched the reference lists of relevant publications as well as meeting abstracts and Conference Proceedings Citation Index to look for additional relevant clinical trials. We included all randomised controlled trials (RCTs) that compared mechanical appendix stump closure (stapler, clips, or electrothermal devices) versus ligation (Endoloop, Roeder loop, or intracorporeal knot techniques) for uncomplicated appendicitis. Two review authors identified trials for inclusion, collected data, and assessed risk of bias independently. We performed the meta-analysis using Review Manager 5. We calculated the odds ratio (OR) for dichotomous outcomes and the mean difference (MD) for continuous outcomes, with 95% confidence intervals (CIs). We included eight randomised studies encompassing 850 participants. Five studies compared titanium clips versus ligature, two studies compared an endoscopic stapler device versus ligature, and one study compared an endoscopic stapler device, titanium clips, and ligature. In our analyses of primary outcomes, we found no differences in total complications (OR 0.97, 95% CI 0.27 to 3.50, 8 RCTs, very low-quality evidence), intraoperative complications (OR 0.93, 95% CI 0.34 to 2.55, 8 RCTs, very low-quality evidence), or postoperative complications (OR 0.80, 95% CI 0.21 to 3.13, 8 RCTs, very low-quality evidence) between ligature and all types of mechanical devices. However, our analyses of secondary outcomes revealed that use of mechanical devices saved approximately nine minutes of total operating time when compared with use of a ligature (mean difference (MD) -9.04 minutes, 95% CI -12.97 to -5.11 minutes, 8 RCTs, very low-quality evidence). However, this finding did not translate into a clinically or statistically significant reduction in inpatient hospital stay (MD 0.02 days, 95% CI -0.12 to 0.17 days, 8 RCTs, very low-quality evidence). Available information was insufficient for reliable comparison of total hospital costs and postoperative pain/quality of life between the two approaches. Overall, evidence across all analyses was of very low quality, with substantial potential for confounding factors. Given the limitations of all studies in terms of bias and the low quality of available evidence, a clear conclusion regarding superiority of any one particular type of mechanical device over another is not possible. Evidence is insufficient at present to advocate omission of conventional ligature-based appendix stump closure in favour of any single type of mechanical device over another in uncomplicated appendicitis.

Two-level agent-based scheduling for a cluster of heating systems

The ongoing decentralization of the electrical power system encompasses the installation of residential electrical loads and generators, such as electro-thermal heating devices. Clusters of these devices in combination with thermal storage can play a significant role in future power system control as they introduce load and generation flexibility into the system. Hence, control concepts which are attractive for both power system level and end user side are required. This work proposes a novel decentralized scheduling approach for electro-thermal heating devices based on a multi-agent system architecture. As a major novelty, the approach addresses both of the aforementioned appeals on two levels without central control. First, local planning with individual objectives is performed. Second, the heating devices cooperate to find the combination of local plans serving best a given energy system objective. This approach is fully decentralized and has a strong end user involvement. The performance of the proposed approach related to end user and system level objectives is compared to that of centralized approaches. Simulation results show that the new method can successfully satisfy end user objectives and provide energy fluctuation balancing. Finally, drawbacks compared to centralized scheduling are analyzed.

Scaling behavior of oxide-based electrothermal threshold switching devices.

Materials exhibiting insulator to metal transition (IMT) and transition metal oxides showing threshold switching behavior are considered as promising candidates for selector devices for crossbar non-volatile memory application. In this study, we use an electrothermal model to simulate the behavior of nanoscale selectors based on several different functional oxides (TaOx, VO2 and NbO2). We extract the device characteristics, such as threshold voltage (VTH), leakage current, device temperature in the ON state, and the size of the conductive filament as a function of selector diameter and functional layer thickness. In addition, we benchmark these devices in a 1 selector/1 resistor (1S1R) cell with a generic phase change-like memory element. These findings provide an insight into how device performance changes with scaling and help with material selection and design of selectors.

3D-FEM electrical–thermal–mechanical analysis and experiment of Si-based MEMS infrared emitters

Designs, simulations, and fabrications of silicon-based MEMS infrared (IR) emitters for gas sensing application are presented. A 3D finite element method (3D-FEM) was used to analyze the coupled electrical–thermal–mechanical properties of a bridge hotplate structure (BHS) IR emitter and closed hotplate structure (CHS) IR emitter using Joule heating and thermal expansion models of COMSOL™. The IR absorptions of n- and p-silicon were calculated for the design of self-heating structure. The BHS and CHS IR emitters were fabricated synchronously using micro-electromechanical systems technology for a direct performance comparison. Both types of IR emitters were characterized by electrical and optical measurements. The experimental results show that BHS IR emitters have higher radiation density, lower power consumption, and faster frequency-response than CHS IR emitters due to the use of a thermal isolation structure and self-heating structure. Meanwhile, the simulated results agree well with the corresponding measured results, which indicate that the 3D-FEM-model is effective and can be used in the optimal design of electro-thermal devices.

In-situ measurement of the heat transport in defect- engineered free-standing single-layer graphene.

Utilizing nanomachining technologies, it is possible to manipulate the heat transport in graphene by introducing different defects. However, due to the difficulty in suspending large-area single-layer graphene (SLG) and limited temperature sensitivity of the present probing methods, the correlation between the defects and thermal conductivity of SLG is still unclear. In this work, we developed a new method for fabricating micro-sized suspended SLG. Subsequently, a focused ion beam (FIB) was used to create nanohole defects in SLG and tune the heat transport. The thermal conductivity of the same SLG before and after FIB radiation was measured using a novel T-type sensor method on site in a dual-beam system. The nanohole defects decreased the thermal conductivity by about 42%. It was found that the smaller width and edge scrolling also had significant restriction on the thermal conductivity of SLG. Based on the calculation results through a lattice dynamics theory, the increase of edge roughness and stronger scattering on long-wavelength acoustic phonons are the main reasons for the reduction in thermal conductivity. This work provides reliable data for understanding the heat transport in a defective SLG membrane, which could help on the future design of graphene-based electrothermal devices.

Comparison of a Hemorrhoidectomy With Ultrasonic Scalpel Versus a Conventional Hemorrhoidectomy.

PurposeA variety of instruments, including circular staplers, ultrasonic scalpels, lasers, and bipolar electrothermal devices, are currently used when performing a hemorrhoidectomy. This study compared outcomes between hemorrhoidectomies performed with an ultrasonic scalpel and conventional methods.MethodsThe study was a randomized prospective review of data available between May 2013 and December 2013, involving 50 patients who had undergone a hemorrhoidectomy for grade III or IV internal hemorrhoids. The hemorrhoidal pedicle was coagulated with an ultrasonic device in the ultrasonic scalpel group (n = 25) and sutured with 3-0 vicryl material after excision in the conventional method group (n = 25).ResultsThe patients' demographics, clinical characteristics, and lengths of hospital stay were similar in both groups. The mean ages of the conventional and the ultrasonic scalpel groups were, respectively, 20.8 ± 1.6 and 22.4 ± 5.0 years (P = 0.240). In comparison with the conventional method group, the ultrasonic scalpel group had a shorter operation time (P < 0.005), less postoperative pain on the visual analogue scale score (for example, P = 0.211 on postoperative day 1), and less postoperative bleeding (P = 0.034). No significant differences in postoperative complications were observed between the 2 groups.ConclusionA hemorrhoidectomy using an ultrasonic scalpel is an effective and safe procedure. The ultrasonic scalpel reduces the operation time, the postoperative blood loss, and the postoperative pain. Long-term follow-up with larger-scale studies is required to evaluate normal activity after a hemorrhoidectomy performed with an ultrasonic scalpel.

Defect-Engineered Heat Transport in Graphene: A Route to High Efficient Thermal Rectification.

Low-dimensional materials such as graphene provide an ideal platform to probe the correlation between thermal transport and lattice defects, which could be engineered at the molecular level. In this work, we perform molecular dynamics simulations and non-contact optothermal Raman measurements to study this correlation. We find that oxygen plasma treatment could reduce the thermal conductivity of graphene significantly even at extremely low defect concentration (∼83% reduction for ∼0.1% defects), which could be attributed mainly to the creation of carbonyl pair defects. Other types of defects such as hydroxyl, epoxy groups and nano-holes demonstrate much weaker effects on the reduction where the sp2 nature of graphene is better preserved. With the capability of selectively functionalizing graphene, we propose an asymmetric junction between graphene and defective graphene with a high thermal rectification ratio of ∼46%, as demonstrated by our molecular dynamics simulation results. Our findings provide fundamental insights into the physics of thermal transport in defective graphene, and two-dimensional materials in general, which could help on the future design of functional applications such as optothermal and electrothermal devices.

Programmable terahertz metamaterials through V-beam electrothermal devices

A reconfigurable THz complex medium, obtained from the embedment of a V-beam electrothermal actuator as a tuning mechanism in a split-ring resonator, is proposed in this paper. When the appropriate actuation voltage is applied on the electrothermal microelectromechanical systems, a controllable metamaterial, presenting enhanced bandwidth tunability at two different resonances, is accomplished. Several polarization arrangements are investigated to enlighten the diverse attributes of the complex medium. The merits of the proposed device are thoroughly examined via a precise finite element method.

Comparison of the Debonding Characteristics of Conventional and New Debonding Instrument used for Ceramic, Composite and Metallic Brackets - An Invitro Study.

Debonding procedure is time consuming and damaging to the enamel if performed with improper technique. Various debonding methods include: the conventional methods that use pliers or wrenches, an ultrasonic method, electrothermal devices, air pressure impulse devices, diamond burs to grind the brackets off the tooth surface and lasers. Among all these methods, using debonding pliers is most convenient and effective method but has been reported to cause damage to the teeth. Recently, a New Debonding Instrument designed specifically for ceramic and composite brackets has been introduced. As this is a new instrument, little information is available on efficacy of this instrument. The purpose of this study was to evaluate the debonding characteristics of both "the conventional debonding Pliers" and "the New debonding instrument" when removing ceramic, composite and metallic brackets. One Hundred Thirty eight extracted maxillary premolar teeth were collected and divided into two Groups: Group A and Group B (n = 69) respectively. They were further divided into 3 subGroups (n = 23) each according to the types of brackets to be bonded. In subGroups A1 and B1{stainless steel};A2 and B2{ceramic};A3 and B3{composite}adhesive precoated maxillary premolar brackets were used. Among them {ceramic and composite} adhesive pre-coated maxillary premolar brackets were bonded. All the teeth were etched using 37% phosphoric acid for 15 seconds and the brackets were bonded using Transbond XT primer. Brackets were debonded using Conventional Debonding Plier and New Debonding Instrument (Group B). After debonding, the enamel surface of each tooth was examined under stereo microscope (10X magnifications). Amodifiedadhesive remnant index (ARI) was used to quantify the amount of remaining adhesive on each tooth. The observations demonstrate that the results of New Debonding Instrument for debonding of metal, ceramic and composite brackets were statistically significantly different (p = 0.04) and superior from the results of conventional debonding Pliers. The debonding efficiency of New Debonding Instrument is better than the debonding efficiency of Conventional Debonding Pliers for use of metal, ceramic and composite brackets respectively.

ENERgized vessel sealing systems versus CONventional hemostasis techniques in thyroid surgery—the ENERCON systematic review and network meta-analysis

Energized vessel-sealing systems have been proposed to save operation time and reduce post-operative complications. The aim of the present systematic review was to compare operation time and postoperative morbidity for ultrasonic and electrothermal bipolar-activated devices with conventional hemostasis techniques and with each other in open thyroidectomy. A systematic literature search (MEDLINE, Cochrane Library, EMBASE and ISI Web of Science) was performed to identify randomised controlled trials (RCTs) comparing conventional hemostasis techniques, ultrasonic devices (Harmonic® scalpel) and/or electrothermal bipolar-activated vessel sealing systems (Ligasure®) during open thyroidectomy. For the primary endpoint (operation time), a network meta-analysis with Bayesian random effects model was performed. Pairwise meta-analyses with random effects were calculated for primary and secondary endpoints. One hundred sixteen publications were evaluated for eligibility; 35 RCTs (4,061 patients) were included. There was considerable methodological and clinical heterogeneity of included trials. The Harmonic scalpel significantly reduced operation time compared with conventional techniques (22.26 min, 22.7 min in the inconsistency model). The use of Ligasure significantly reduced operation time in total thyroidectomy (13.84 min in the consistency model, 12.18 min in the inconsistency model). In direct comparison, operations with the Harmonic scalpel were faster than with Ligasure (8.42 min in the consistency model, 2.45 min in the inconsistency model). The rates of recurrent nerve palsy and postoperative hypocalcaemia did not significantly differ in the intervention groups. This meta-analysis shows superiority of ultrasonic devices in terms of operation time compared with conventional hemostasis techniques in thyroid surgery, with no detriment to safety outcomes.

Fabrication of robust electrothermal MEMS devices using aluminum–tungsten bimorphs and polyimide thermal isolation

We report a novel fabrication process for bimorph based electrothermal devices that involves surface and bulk micromachining on an SOI (silicon-on-insulator) wafer. The bimorph transducers consist of aluminum (Al)-–tungsten (W) beams with a thin layer of SiO2 encapsulating the W-layer and electrically isolating it from the Al-layer. The widely different coefficients of thermal expansion (CTE) of Al and W ensure high bimorph sensitivity. The W-layer acts as an active layer of the bimorph and also as a resistive heater for actuation by Joule heating. Proof mass and rigid beams can be incorporated into the design by utilizing the device layer of the wafer. Thermal isolation between the bimorphs and the substrate; and between bimorphs and the proof mass or rigid beams is achieved by a spin-coated polyimide layer. The process ensures improved robustness compared to comparable designs that typically utilize SiO2 thin-film for thermal isolation. The process can be adapted to a wide range of electrothermal devices, and enables design and layout engineers to trade off speed for achieving lower power consumption and vice versa. We report fabrication and test results on 1D (one-dimensional) electrothermal scanning micromirrors. The fabricated devices have significantly better robustness compared to previously reported mirrors with Al-SiO2 bimorphs and SiO2 thermal isolation.

Effectiveness of electrothermal bipolar vessel-sealing devices versus other electrothermal and ultrasonic devices for abdominal surgical hemostasis: a systematic review

Adequate hemostatic techniques are essential for optimal intra- and postoperative results. A number of different hemostatic techniques and devices have been developed over the past few years, but which device should be preferred during laparoscopic and open abdominal procedures? We conducted a systematic search for randomized controlled trials (RCTs) that compared the effectiveness and costs of vessel-sealing devices with those of other electrothermal or ultrasonic devices in abdominal surgical procedures. Seven RCTs that included 554 patients met the inclusion criteria. Various procedures that used a vessel-sealing device (LigaSure™) (n = 264) were compared to ultrasonic devices (n = 139) and mono- (n = 20) or bipolar devices (n = 130). LigaSure was favored in two studies with respect to less blood loss, shorter operating time, and lower costs. However, no differences were observed in the other studies. Considering the relatively low number of complications, all hemostatic devices used may be considered relatively safe. None of the studies reported on quality of life or cost effectiveness. Vessel-sealing devices may be considered safe and their use may reduce costs due to reduced blood loss and shorter operating time in some abdominal surgical procedures compared to mono- or bipolar electrothermal devices. Wider-ranging RCTs of sufficient quality that assess (cost) effectiveness are required to make firm conclusions.

TCR Sign Variation of Surface Micromachined Polysilicon Resistor under Joule Self-Heating

This work reports the sign variation of temperature coefficient of surface micromachined polysilicon resistor due to Joule self-heating effect. It was found that the sign of temperature coefficient of polysilicon resistor with initial negative temperature coefficient value varies two times from negative to positive and then from positive to negative with the consumed power increasing, while the sign of the temperature coefficient of polysilicon resistor with initial positive value only changes once to negative. The experiment results indicate that much more attention should be paid to the temperature coefficient of polysilicon resistor for the surface micromachined electrothermal polysilicon devices.

Modeling of an Ablation-Free Electrothermal Plasma Pellet Accelerator

Electromagnetic and electrothermal launch devices can provide high acceleration and inject pellets with speeds in excess of 3 km/s for masses up to 3gm. However, the ablation of the bore adds impurities to the plasma. An ablation-free electrothermal pellet accelerator is a concept that utilizes an ablation-free capillary discharge in which a quartz capillary is coated with a nanocrystalline diamond film (NCD). The ablation-free capillary connects to an extension tube, which is also an ablation-free quartz tube coated with NCD that serves as the acceleration barrel. An ablation-free capillary discharge computer code has been developed to model plasma flow and acceleration of pellets for fusion fueling in magnetic fusion reactors. The code incorporates ideal and non-ideal conductivity models and has a set of governing equations for the capillary, the acceleration tube, and the pellet. The capillary generates the plasma from hydrogen/deuterium gas when the discharge current flows through the capillary. The pellet starts moving in the extension tube when the pressure of the plasma flow from the capillary reaches the release limit. The code results show an exit velocity of 2.7 km/s for a 20 mg deuterium pellet when using a capillary and barrel each 9 cm long where the source and barrel diameters are 0.4cm and 0.6cm, respectively, with a discharge current of 20 kA over a 300 both the capillary and the barrel to 12 cm increases the pellet exit velocity to 2.9 km/s, and a further increase to 18cm results in a 3.15km/s pellet exit velocity. Increasing the barrel length to 36 cm, while keeping the source length at 18 cm, results in an increase in the pellet velocity to 3.32 km/s. The pellet starts moving at 35 μs reaches 3.32 km/s in 100 this velocity until exiting the acceleration tube.

Analysis of Hybrid Electrothermomechanical Microactuators With Integrated Electrothermal and Electrostatic Actuation

The goal of this paper is to integrate electrothermal and electrostatic actuations in microelectromechanical systems (MEMS). We look at cases where these two types of actuation are intimately coupled and argue that such integrated electrothermomechanical (ETM) microactuators have more advantages than pure electrothermal or electrostatic devices. We further propose a framework to model hybrid ETM actuation to get a consistent solution for the coupled mechanical, thermal, and electrical fields in the steady state. Employing a Lagrangian approach, the inhomogeneous current conduction equation is used to describe the electric potential, while the thermal and displacement fields are obtained by solving the nonlinear heat conduction equation and by performing a large deformation mechanical analysis, respectively. To preserve numerical accuracy and reduce computational time, we also incorporate a boundary integral formulation to describe the electric potential in the medium surrounding the actuator. We show through the example of a hybrid double-beam actuator that ETM actuation results in low-voltage low-power operation that could be used for switching applications in MEMS. We also extend the same device toward bidirectional actuation and demonstrate how it may be used to overcome common problems like stiction that occur in MEMS switches.