Through Holes Research Articles

One-pot/one-step synthesis of Bi2O3/ZnO/Pd nanocomposite for preconcentration and determination of some heavy metal ions in different samples

ABSTRACT In this contribution, a new green eco-friendly synthesised nanocomposite (Bi2O3/ZnO/Pd) was fabricated by one-pot/one-step method, using ultrasonic waves. The nanocomposite was used for pre-concentration of some heavy metals, i.e. cadmium (II), lead (II), and copper (II), exploiting ultrasound-assisted dispersive micro solid phase extraction (UA-D-μ-SPE) method, before their determination by flame atomic absorption spectroscopy (FAAS). The adsorbent synthesis was confirmed by XRD, SEM, BET, TEM, EDS, and TGA analyses. The central composite design (CCD) method was employed to optimise various parameters affecting the extraction of heavy metals. The effective parameters in the adsorption process, viz. the amount of adsorbent (16 mg), pH of the sample solution (6.2), and adsorption time (4 min), were optimised. The type and the concentration of eluting agent (HCl solution) was investigated as one parameter at a time. Impressive parameters in the desorption stage such as the volume and concentration of eluting solution (400 μL of 0.8 mol L−1 HCl) and desorption time (2.5 min) were optimised. In the best extraction conditions for cadmium (II), lead (II), and copper (II), the limits of detection (LODs) were 0.75, 2.1, and 0.90 ng mL−1; the limits of quantification (LOQs) were 2.5, 7.0, and 3.0 ng mL−1; the linear dynamic ranges (LDRs) were 2.5–100, 7.0–600, and 3.0–250 ng mL−1; preconcentration factors (PF) were 24.10, 25.20, and 25.39; and the relative standard deviations (RSDs%) were 3.7, 4.1, and 3.8 (n = 5), respectively. Additionally, the adsorbent had the ability to extract metals up to 8 times without a significant decrease in the extraction percentages. The adsorbent was successfully used in the determination of cadmium (II), lead (II), and copper (II) ions in different food, biological, cosmetic, and water samples.

Optimized DC–DC converter based on new interleaved switched inductor capacitor for verifying high voltage gain in renewable energy applications

This paper introduces an optimized DC–DC converter that employs a modified switched inductor-capacitor technique to achieve ultra-high voltage gain for renewable energy systems. The development is based on adding one cell of modified switched inductor (MSL1) with series diodes interleaved with the main switch in the proposed DC–DC converter. The (MSL1) with capacitor operates in resonant mode to reduce current stress across the main switch when the charge in capacitor becomes zero. This approach also reduces voltage stress across the main switch, all inductors, and diodes. Furthermore, modified switched inductors (MSL2) with an auxiliary switch and a coupled capacitor are incorporated to provide double boosting voltage and to achieve high voltage gain. Additionally, a main and auxiliary switch are integrated with modified switched capacitors (MSC) to provide ultra-high voltage gain and to reduce voltage stress across auxiliary switch. Moreover, the proposed converter exhibits a continuous input current with zero pulsating, even at very low duty cycles. The advantages of the proposed converter are high efficiency, low voltage stress, and low values of inductors and capacitors when utilizing a high switching frequency. A mathematical model for the proposed converter is developed for both continuous conduction mode and discontinuous conduction mode. In addition, the PCB design for the proposed converter is presented, and experimental tests are conducted to verify the simulation and laboratory results. The proposed converter aims to boost the voltage from 20 to 40 V to a variable output voltage between 200 and 400 V, delivering 400 watts of power with an efficiency of 96.2%.

(Invited) Modified SAB Methods for Hybrid and All-Cu Bonding for 3D Integration below 200ºC

Two Surface Activated Bonding (SAB) methods will be proposed to enable low-temperature hybrid bonding for 3D integration. A modified one involves surface activation processes using Ar fast-atom-beam bombardment with simultaneous co-sputtering of Si nano-adhesion layer, followed by sequential plasma irradiation with N2 radicals. In the other one, we will connect two device wafers not in a hybrid but all-Cu bonding. A small insulation area surrounds the Cu pads on the wafer, while the rest is covered with Cu solid layers. These solid layers constitute the ground plane, power plane, or their paired layers and may contribute to heat dissipation when connected to thermal vias. The two wafers are connected only by bonding on the Cu electrodes and solid layers. Cu-Cu direct bonding is possible at room temperature by applying the standard SAB directly. Room-temperature bonding is overwhelmingly advantageous for bonding heterogeneous devices and wafers.

Bending analysis of glass fiber reinforced epoxy composites/copper-clad laminates for multi-layer printed circuit boards

Printed circuit board (PCB) is the most important part of any electronic device which is made of copper-clad laminate and glass fiber-reinforced composites. Since the ply orientation of fiber-reinforced composites and lamina thickness have a significant influence on the mechanical properties of the whole composite laminate it is necessary to investigate the effects of ply orientation and lamina thickness on the bending properties of PCB so that they can be manufactured to meet the service requirements. In this work, the bending properties of PCB were investigated for seven different ply orientations of glass fiber-reinforced composite laminas and for eight different thickness combinations (for a constant laminate thickness) of glass fiber-reinforced composite lamina and copper-clad laminate. A commercially available finite element analysis software (Abaqus) was used to simulate a three-point bending test of PCBs and the simulation results were validated using experimental results. It is found that the bending stiffness is maximum for the cross-ply laminate. The introduction of angle ply improves the maximum von-Mises stress of the PCB with an insignificant cost of bending stiffness (less than 5% reduction). It is found that the bending stiffness and the maximum von-Mises stress of the PCB can be regulated through the variation of thickness of the constituent lamina. The laminate stiffness can be increased by increasing the thickness of stiffer laminas or by placing the stiffer laminas towards the surface of the laminate. The outcome of this research would provide a comprehensive understanding of the bending characteristics of the multi-layered PCBs which can be directly utilized by the PCB manufacturers. However, the effects of ply orientation and lamina thickness variation on the behavior of the PCBs subject to temperature variation, impact loading, vibration, and other conditions that might affect the service life of the PCBs should be investigated.

Proximity hybridization induced bipedal DNA walker for label-free electrochemical detection of apolipoprotein A4 based on DNA meditated Ag nanoparticles growth

Apolipoprotein A4 (Apo-A4) is considered as a prospective molecular biomarker for diagnosis of depression due to its neurosynaptic toxicity. Here, we propose a neighboring hybridization induced catalyzed hairpin assembly (CHA) driven bipedal DNA walker that mediates hybridization of Ag nanoparticles (Ag NPs) with DNA probes for highly sensitive electrochemical quantitative detection of Apo-A4. Driven by CHA, this bipedal DNA walker can spread all over the surface of the sensor, induce the HP1-HP2 double chain structure, make the surface of the sensor negatively charged, and adsorb a large number of Ag ions. After chemical reduction with hydroquinone, the Ag NPs formed provide signal tracers for electrochemical dissolution analysis of the target. The Ag NPs formed by chemical reduction of hydroquinone can provide signal traces for electrochemical stripping analysis of target thrombin. The linear range of this method is from 10 pg mL−1 to 1000 ng mL−1, and the detection limit is 5.1 pg mL−1. This enzyme-free and labeling detection method provides a new strategy for rapid clinical detection of Apo-A4 and accurate identification of depression.

Surface‐Engineered Liquid Metal Particles for Printing Stretchable Conductive Composites with Enhanced Stability Under Different Strain Rates

AbstractIntegrating liquid metal (LM) particles into compliant polymers presents an innovative approach for developing intelligent and adaptable systems in stretchable electronics, wearable devices, soft robotics, and other emerging technologies. However, the inherent electrically insulative nature of these solid‐liquid composites, compounded by the gallium oxide shell surrounding LM droplets, poses a significant challenge in establishing conductive pathways, especially for small droplet sizes and ultrasoft elastomers. Here, an interface modification approach that addresses this bottleneck and enables the synthesis of highly stretchable and printable composites with LM microparticles (<2 µm) is presented. Polyvinylpyrrolidone (PVP) is used to functionalize these small LM inclusions, weakening the particle‐matrix interface, and facilitating the formation of a conductive percolating network under tensile strain. Optimized synthesis parameters result in printed conductive traces with excellent electrical conductivity (0.2 Ω cm−1), ultra‐high elongation at break (>900% strain), and minimal resistance change (≈131%). Furthermore, this comprehensive study of the electromechanical response of these stretchable conductors under various strain rates reveals their exceptional stability under dynamic loading conditions, surpassing the performance of conductive traces composed of sprayed liquid metal. Finally, the potential application of these multifunctional materials in stretchable circuitry, addressing the demand for high stretchability and stability in wearable electronics, is demonstrated.

Magnetically tunable zero-index metamaterials

Zero-index metamaterials (ZIMs) feature a uniform electromagnetic mode over a large area in arbitrary shapes, enabling many applications including high-transmission supercouplers with arbitrary shapes, direction-independent phase matching for nonlinear optics, and collective emission of many quantum emitters. However, most ZIMs reported to date are passive; active ZIMs that allow for dynamic modulation of their electromagnetic properties have rarely been reported. Here, we design and fabricate a magnetically tunable ZIM consisting of yttrium iron garnet (YIG) pillars sandwiched between two copper clad laminates in the microwave regime. By harnessing the Cotton–Mouton effect of YIG, the metamaterial was successfully toggled between gapless and bandgap states, leading to a “phase transition” between a zero-index phase and a single negative phase of the metamaterial. Using an S-shaped ZIM supercoupler, we experimentally demonstrated a tunable supercoupling state with a low intrinsic loss of 0.95 dB and a high extinction ratio of up to 30.63 dB at 9 GHz. We have also engineered a transition between the supercoupling state and the topological one-way transmission state at 10.6 GHz. Our work enables dynamic modulation of the electromagnetic characteristics of ZIMs, enabling various applications in tunable linear, nonlinear, quantum, and nonreciprocal electromagnetic devices.

Grafting Amino Groups onto Polyimide Films in Flexible Copper-Clad Laminates Using Helicon Plasma.

Polyimide (PI) films are widely used in electronic devices owing to their excellent mechanical and electrical properties and high thermal and chemical stabilities. In particular, PI films play an important role in flexible printed circuit boards (FPCBs). However, one challenge currently faced with their use is that the adhesives used in FPCBs cause a high dielectric loss in high-frequency applications. Therefore, it is envisioned that PI films with a low dielectric loss and Cu films can be used to prepare two-layer flexible copper-clad laminates (FCCLs) without any adhesive. However, the preparation of ultra-thin FCCLs with no adhesives is difficult owing to the low peel strength between PI films and Cu films. To address this technical challenge, an FCCL with no adhesive was prepared via high-power helicon wave plasma (HWP) treatment. Field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were tested. Also, the surface roughness of the PI film and the peel strength between the PI film and Cu film were measured. The experimental results show that the surface roughness of the PI film increased by 40-65% and the PI film demonstrated improved adhesion (the peel strength was >8.0 N/cm) with the Cu film following plasma treatment and Cu plating.

An Enhanced Interlayer Construction Strategy for High‐Frequency Copper Clad Laminates: Resolving the Contradiction between Signal Loss and Adhesion

AbstractIn high‐frequency printed circuit boards (PCBs), there is an inherent contradiction between minimizing signal loss and maximizing adhesion strength. To tackle this issue, this work presents a simple approach by developing an enhanced interlayer through a two‐step process involving anodization/APTES (3‐aminopropyltriethoxysilane) treatment. The anodization yields micro/nano oxide structures with low surface roughness, thereby reducing the skin effect. One side of the enhanced interlayer is mechanically anchored and chemically bonded to copper foils, while the other side is coupled with bismaleimide/triazine‐based resins (BT resins), significantly augmenting the adhesion strength. Eight‐layer PCBs manufactured employing this method exhibit an insertion loss of −1.3553 dB in−1 at 32 GHz. Compared to two conventional brown oxide methods, the insertion loss is reduced by 7.80% and 3.24%, respectively, with a more substantial reduction observed at higher frequencies. The peel strength of samples ranges from 0.554 to 0.589 N mm−1, demonstrating maximum enhancements of 34.78% and 164.13% in comparison to the two brown oxide methods, respectively. Moreover, eight‐layer PCBs undergo lead‐free reflow soldering tests, solder float tests, and thermal fatigue tests without encountering any failures. Consequently, the proposed method holds significant practical significance in addressing the challenge associated with low signal loss and high adhesion strength in high‐frequency PCBs.

Ultra high voltage gain non-isolated DC-DC converter based on new interleaved triple boosting technique

This paper introduces a DC-DC converter that employs a modified triple boosting architecture (MTB), interleaved with modified switched inductor capacitors (MSIC), to achieve ultra-high voltage gain in photovoltaic applications. The converter design also includes a modified switched inductor with a modified voltage multiplier mode (MVM), which interleaves with the main switch and effectively doubles the voltage transfer gain. Furthermore, a modified triple boosting mode technique, utilizing interleaved components and an auxiliary switch, is integrated into the converter design. The main switch and auxiliary switch, combined with modified voltage multiplyer, contribute to achieving high voltage gain. The proposed converter offers numerous advantages. It exhibits remarkable efficiency while ensuring low voltage stress across diodes and MOSFETs. Moreover, by utilizing low inductance and capacitance values at high switching frequencies, the converter’s overall performance is enhanced. To validate and substantiate the simulation and laboratory results, the converter has undergone PCB design and experimental testing. Specifically, this converter is designed to boost input voltage levels ranging from 30 V to 40 V to a variable output voltage between 200 V and 400 V, with a power output of 360 W and an efficiency rating of 96.5%.

ADVANTAGES OF VIRTUAL MODELING FOR THE DEVELOPMENT OF MEASURING DEVICES

The relevance of using virtual modeling of devices for engineering design is considered. An analysis of the publication on the application of computerized design technologies in the processes of device development was made. The possibilities and ways of using computer modeling in the process of developing devices in the Proteus Design and SolidWorks software environments are indicated. In the Proteus Design software environment, you can simulate the operation of electrical circuits containing programmable devices: microcontrollers and microprocessors, as well as design a printed circuit board. A large number of virtual tools are used to simulate the circuits, which simulate the operation of measuring devices, which facilitates the development of electrical circuits. The ARES PCB design module has an autorouter that allows you to automate the design process. As a result of the design of the printed circuit board, a pattern of tracks is obtained, which is used for the manufacture of the printed circuit board by various methods. The article demonstrates all the stages of designing an electronic device. On the basis of the comparison of the simulation results and the operation of the manufactured device, conclusions are made about the effectiveness of the application of simulation in the engineering design of electronic measuring devices.

Oxidative stress responses to heavy metal burden in African catfish (<i>Clarias gariepinus</i>) from Warri River, Niger-Delta, Southern Nigeria

Despite the degradation and threat of ubiquitous contaminants, such as heavy metals, in Warri River, Southern Nigeria, little is known about the ecological effects of such pollution using pro-oxidant variables. This study investigated oxidative stress responses to heavy metals (lead (Pb), cadmium (Cd), manganese (Mn), nickel (Ni) and copper (Cu)) burden in the heart, kidney, liver and gills of African catfish inhabiting Warri River. Fish (N=30) were collected during August-September, 2018 from two contaminated sites along the course of Warri River and a fish farm which was considered a reference site. The concentrations of Pb, Cd and Ni in the two contaminated sites were above the WHO permissible limits and significantly higher (p<0.05) as compared to the fish collected from the reference site. The trend of accumulation of the metals followed the order: Reference site (site 1)-Mn>Ni>Cu>Pb>Cd; site 2-Pb>Cu>Cd>Mn>Ni and site 3-Ni>Mn>Cu>Cd and Pb respectively. The activities of catalase (CAT) and superoxide dismutase (SOD) were significantly higher (p<0.05) in the organs of fish caught at the two contaminated sites. Malondialdehyde (MDA) was significantly elevated (p<0.05), in the liver and heart of fish obtained from site 3, relative to sites 2 and 1. Fish obtained from the two contaminated sites had significantly decreased (p<0.05) levels of reduced glutathione (GSH) in their organs, however, the reduction was more in site 2. The results of this study confirm that environmental stressors, such as heavy metals, can alter antioxidant enzymes and glutathione systems, as well as induce lipid peroxidation, leading to oxidative stress in aquatic organisms.

A New Hybrid Modular Multilevel Rectifier as MVac–LVdc Active Front-End Converter for Fast Charging Stations and Data Centers

As the power demands from DC energy-storage and loads continue to grow in electric vehicle (EV) fast charging stations and data centers, the power delivery infrastructure faces challenges with the installation of bulky, heavy, and slow responsive line-frequency power transformer (LFT). These transformers are required to step-down the feeder voltage from medium-voltage (MV) ac grid-service to low-voltage (LV) ac, followed by LVac-LVdc rectifiers. This approach results in a large equipment footprint, heavy conductor copper usage, and lower efficiency. Consequently, there is increasing interest in exploring direct interface from MVac to LVdc without the need for LFT. This paper proposed a new solution called MVac-LVdc hybrid modular multilevel rectifier (HMMR). The HMMR serves as a centralized step-down active front-end converter, enabling power delivery to LVdc with a reduced number of dc/dc back-end isolated converters. Compared to the modular multilevel converter (MMC) used as the MVac interface solution, the proposed HMMR could save the submodule number by 40%, reduce losses by 22%, and significantly reduce the footprint area by 37%, effectively increasing the power density and reducing the construction cost. Moreover, the proposed HMMR has the potential to operate in both unity and non-unity power factor modes, allowing it to provide the grid-support functionality. The performance of HMMR is evaluated and compared with full-bridge MMC in the case of 13.8 kV ac to 6 kV dc. The feasibility of the proposed converter is verified by the simulation results with the same specifications. Finally, a scale-down 1.4 kV HMMR prototype is developed to validate the effectiveness of the proposed converter.

Health Monitoring System from Pyralux Copper-Clad Laminate Film and Random Forest Algorithm.

Sensor technologies have been core features for various wearable electronic products for decades. Their functions are expected to continue to play an essential role in future generations of wearable products. For example, trends in industrial, military, and security applications include smartwatches used for monitoring medical indicators, hearing devices with integrated sensor options, and electronic skins. However, many studies have focused on a specific area of the system, such as manufacturing processes, data analysis, or actual testing. This has led to challenges regarding the reliability, accuracy, or connectivity of components in the same wearable system. There is an urgent need for studies that consider the whole system to maximize the efficiency of soft sensors. This study proposes a method to fabricate a resistive pressure sensor with high sensitivity, resilience, and good strain tolerance for recognizing human motion or body signals. Herein, the sensor electrodes are shaped on a thin Pyralux film. A layer of microfiber polyesters, coated with carbon nanotubes, is used as the bearing and pressure sensing layer. Our sensor shows superior capabilities in respiratory monitoring. More specifically, the sensor can work in high-humidity environments, even when immersed in water-this is always a big challenge for conventional sensors. In addition, the embedded random forest model, built for the application to recognize restoration signals with high accuracy (up to 92%), helps to provide a better overview when placing flexible sensors in a practical system.

Liquid Phase Graphene Exfoliation with a Vibration-Based Acoustofluidic Effector.

Liquid phase exfoliation (LPE) has emerged as a promising method for the industrial-scale production of graphene. However, one of its critical steps, namely sonication, has faced challenges due to high power consumption and low efficiency, leading to limited applicability in industrial settings. This study introduces a novel, cost-effective microfluidic sonication device designed to significantly reduce power consumption while efficiently assisting the LPE process for graphene production. By coupling a capillary with a buzzer and applying an appropriate electric signal, simulation and particle tracing experiments reveal the generation of robust shear forces resulting from acoustic streaming and cavitation when the capillary end is immersed in the liquid. For the first time, the capillary-based sonication device was effectively utilized for graphene exfoliation in a DMF (N,N-Dimethylformamide) + NaOH liquid phase system. The SEM (Scanning Electron Microscope) and Raman characterization results corroborate the successful exfoliation of 100 nm with thicknesses below 10 nm graphene sheets from graphite flakes using this pioneering device. The values of I2D/IG increase after processing, which suggests the exfoliation of graphite flakes into thinner graphene sheets. The vibration-based acoustofluidic effector represents a versatile and scalable miniature device, capable of being employed individually for small-batch production, thereby optimizing the utilization of raw 2D materials, particularly in experimental scenarios. Alternatively, it holds the potential for large-scale manufacturing through extensive parallelization, offering distinct advantages in terms of cost-efficiency and minimal power consumption.

Association between female circulating heavy metal concentration and abortion: a systematic review and meta-analysis.

This study aimed to evaluate the association between blood heavy metal (zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd)) concentrations and spontaneous abortion (SA) and recurrent pregnancy loss (RPL) and explore the possible endocrine dysfunction associated with it. A literature search was performed in the PubMed, Embase, Cochrane Library, and Web of Science databases up to April 2023. The overall effects were expressed as the standard mean difference (SMD). Subgroup analysis was performed according to the type of abortion (SA or RPL). Stata 16.0 was utilized for data analysis. Based on the integrated findings, abortion women showed significantly lower Zn (SMD = -1.05, 95% CI: -1.74 to -0.36, p = 0.003) and Cu concentrations (SMD = -1.42, 95% CI: -1.97 to -0.87, p <0.001) and higher Pb (SMD = 1.47, 95% CI: 0.89-2.05, p <0.001) and Cd concentrations (SMD = 1.15, 95% CI: 0.45-1.85, p = 0.001) than normal pregnant women. Subgroup analysis showed that Zn and Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with RPL, whereas Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with SA. Zn and Cu deficiencies and Pb and Cd exposure were associated with abortion. Endocrine dysfunction, such as insulin resistance, vitamin D insufficiency, and abnormal thyroid and sex hormone concentrations, is thought to be involved in heavy metal-related abortion.

High peel strength and excellent solder heat‐resistance epoxy adhesive for flexible copper clad laminate

AbstractFlexible copper clad laminate (FCCL), commonly composed of copper foil, epoxy adhesive, and polyimide (PI) film, is widely used as the substrate material of flexible printed circuit boards. Carboxyl‐terminated acrylonitrile butadiene (CTBN) and four curing agents were used to prepare the modified epoxy adhesive. FCCL's peel strength was improved by treating PI with plasma. The results showed that when the epoxy adhesive was toughened by adding 30 phr CTBN and PI film was treated with nitrogen plasma, the comprehensive performance of the modified epoxy adhesive and FCCL was the best. The impact strength of the modified epoxy adhesive was 39.32 kJ m−2 (149.7% higher than that of the unmodified), and the gelation time was 330 s at 160°C. The peel strength of FCCL was 1.29 kgf cm−1, which was higher than required. It can pass the lead‐free solder heat‐resistance test at 320°C 10 s−1 as well. A new way is provided to expand the application of FCCL in areas requiring higher peel strength.

An adaptive laser processing method of multilayer heterogeneous materials by monitoring dynamic spectrum at kHz-MHz level

Laser micro/nano processing exhibits significant advantages in manufacturing capability and performance. However, the properties of ablated materials cannot be sensed and identified during processing is an intractable challenge. In particular, multilayer heterogeneous materials often evolve into excessive residues and damages during laser selective removal. In this study, we developed an adaptive laser processing method that includes material interface adaptive and laser power adaptive for selective removal of multilayer heterogeneous materials by monitoring dynamic spectrum at kHz-MHz level. The mechanism of interface sensing and the threshold of laser selective removal of multilayer materials were investigated. Dual-channel parallel detection mode of the blazed grating with the ultrafast photodetector at the kHz-MHz pulse level has been designed and verified for monitoring adjacent layers synchronously. High-speed signals with a pulse width of 30 ns and a repetition frequency of 0–15 MHz were identified by the Field Programmable Logic Gate Array (FPGA), and pulse-level closed-loop feedback was finished. Patterned selective removal on an FR-4 copper clad laminate (CCL) and flexible printed circuit (FPC) was completed. The method exhibited sensitive signal characteristics, accurately sensed the material interface, and provided a clear criterion for identifying the removal process of multilayer materials by quantitative analysis of signal variation, which provides an innovative scheme for laser intelligent manufacturing of multilayer heterogeneous materials.

A Printing Strategy for Embedding Conductor Paths into FFF Printed Parts.

A novel approach to manufacture components with integrated conductor paths involves embedding and sintering an isotropic conductive adhesive (ICA) during fused filament fabrication (FFF). However, the molten plastic is deposited directly onto the adhesive path which causes an inhomogeneous displacement of the uncured ICA. This paper presents a 3D printing strategy to achieve a homogeneous cross-section of the conductor path. The approach involves embedding the ICA into a printed groove and sealing it with a wide extruded plastic strand. Three parameter studies are conducted to obtain a consistent cavity for uniform formation of the ICA path. Specimens made of polylactic acid (PLA) with embedded ICA paths are printed and evaluated. The optimal parameters include a groove printed with a layer height of 0.1 mm, depth of 0.4 mm, and sealed with a PLA strand of 700 µm diameter. This resulted in a conductor path with a homogeneous cross-section, measuring 660 µm ± 22 µm in width (relative standard deviation: 3.3%) and a cross-sectional area of 0.108 mm2 ± 0.008 mm2 (relative standard deviation 7.2%). This is the first study to demonstrate the successful implementation of a printing strategy for embedding conductive traces with a homogeneous cross-sectional area in FFF 3D printing.

Laser diode based THz-TDS system with 133 dB peak signal-to-noise ratio at 100 GHz

Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful and versatile tool in various scientific fields. These include—among others—imaging, material characterization, and layer thickness measurements. While THz-TDS has achieved significant success in research environments, the high cost and bulky nature of most systems have hindered widespread commercialization of this technology. Two primary factors contributing to the size and cost of these systems are the laser and the optical delay unit (ODU). Consequently, our group has focused on developing THz-TDS systems based on compact monolithic mode-locked laser diodes (MLLDs). The ultra-high repetition rate (UHRR) of the MLLD has the added benefit that it allows us to utilize shorter ODUs, thereby reducing the overall cost and size of our systems. However, achieving the necessary precision in the ODU to acquire accurate terahertz time-domain signals remains a crucial aspect. To address this issue, we have developed and enhanced an interferometric extension for UHRR-THz-TDS systems. This extension is inexpensive, compact, and easy to incorporate. In this article, we present the system setup, the extension itself, and the algorithmic procedure for reconstructing the delay axis based on the interferometric reference signal. We evaluate a dataset comprising 10,000 signal traces and report a standard deviation of the measured terahertz phase at 1.6 THz as low as 3 mrad. Additionally, we demonstrate a remaining peak-to-peak jitter of only 20 fs and a record-high peak signal-to-noise ratio of 133 dB at 100 GHz after averaging. The method presented in this paper allows for simplified THz-TDS system builds, reducing bulk and cost. As a result, it further facilitates the transition of terahertz technologies from laboratory to field applications.