Search Results (156)

Flexible and biocompatible sensors are vital for a wide range of biomedical applications, including real-time health monitoring, intracranial pressure monitoring, knee replacement surgeries, wearables, and smart prosthetics. While various highly sensitive and stable pressure sensors have been demonstrated, they often lack the conformability and biocompatibility crucial for their wider application in various bio-integrated electronic systems. Herein, a piezoelectric pressure sensor is proposed using a hybrid polymer composite by leveraging the unique properties of Chitosan and Parylene C. Various material characterisations, such as XRD and FTIR, were performed to reveal structural and chemical characteristics of the novel composite material. Next, electromechanical characterisations of the pressure sensor were performed to reveal its dynamic sensing properties. The pressure sensor exhibits excellent sensitivity for both pressure and frequency, as well as cyclic stability (10³ cycles), wide pressure range (20–70 kPa), and biocompatibility. Full article

This study presents a sustainable strategy for developing high-performance supercapacitor separators through the upcycling of waste newspapers into functional cellulose-based membranes. The intrinsic porous architecture of cellulose fibers was exploited as a robust scaffold, onto which Parylene C and polyaniline (PANI) layers were sequentially introduced to reinforce mechanical integrity and enhance electrochemical functionality. The resulting dual-layer configuration exhibited significantly improved interfacial stability and ion-transport characteristics compared with conventional polyethylene separators. Comprehensive structural and electrochemical analyses verified that the synergistic combination of Parylene C and PANI coatings effectively optimized separator–electrolyte interfacial properties and reduced impedance. Beyond performance enhancement, this work establishes an environmentally responsible route for valorizing paper waste, offering a viable pathway toward sustainable energy storage technologies. Full article

High-resolution, multi-modal neural interfaces are essential for advancing systems neuroscience and brain–computer interface technologies. This study designed and fabricated a 128-channel comb-shaped flexible micro-electrode array. The device integrates a biocompatible Parylene substrate with a flexible thin-film microprobe array, enabling simultaneous recording of electrocorticography (ECoG), intracortical local field potentials (LFP), and neuronal action potentials (spikes) from the cortical surface and superficial layers. Microelectrode sites were modified with platinum black nanoparticles, significantly reducing impedance. In vivo experiments in rats demonstrated the array’s ability to capture high-fidelity signals across different recording depths. Key findings included the acquisition of opposing LFP trends and polarity reversals between adjacent channels, reflecting local microcircuit dynamics. The array also reliably recorded neural activity during audiovisual cross-modal sensory stimulation. These results validate the device as an effective tool for multi-scale electrophysiology, successfully balancing high spatial resolution and signal quality with minimal tissue invasiveness, thereby offering significant potential for fundamental research and neural engineering applications. Full article

Plasma regeneration was investigated as a means of regenerating microstructures on biosensors for repeated use. These microstructures were based on the deposition of suspensions containing polymer microspheres. While this method provides a simple way to structure surfaces, obtaining regular structures in a reproducible way remains a challenge. Therefore, it would be advantageous to be able to reuse regular structures, which requires regeneration. To investigate this concept, surface acoustic wave (SAW) resonators were structured using 5 µm and 20 µm polystyrene microspheres and coated with parylene C to stabilize the particle structures. After use in bioanalytical experiments, the biological residues and the parylene C cover layer were removed with plasma, and a new parylene C layer was added. Both atmospheric and low-pressure plasma were tested for regeneration. As a result, the low-pressure plasma was to be preferred because it did not damage the transducer structures on the SAW resonators, unlike the atmospheric plasma. Water contact angle measurements and transmission spectra recorded with a network analyzer confirmed that freshly prepared and regenerated structured SAW resonators coated with parylene C exhibited similar wetting properties and resonance parameters. Therefore, plasma regeneration is an effective way to enable the reuse of perfectly structured SAW resonators. Full article

Parylene C films are subjected to inadequate corrosion resistance due to their relatively low adhesion and structural defects. To address this challenge, the CVD Parylene C film (10 μm thick) was composited with Al₂O₃ film (30 nm thick) prepared with atomic layer deposition (ALD) technology in this work. Optical microscopic results indicate uniform thickness of the films and the reduced adhesion of Parylene C based thick films. SEM-EDX and AFM results show that the composite films have more blurred mounds morphology than the individual films, and Al₂O₃ film decreases the surface roughness of Parylene C film; compared with the single-layer film, the R_a value of the bilayer film decreased by approximately 6%. XPS, FTIR and XRD analyses confirm the structural components of Al₂O₃ and Parylene C films and the annealing effect of ALD process on Parylene C film. Tafel polarization and electrochemical impedance spectroscopy tests reveal that the 304-Parylene C–Al₂O₃ system exhibits the optimal corrosion resistance; its corrosion current density (i_corr) is 8.099 × 10⁻⁵ μA/cm² and the ALD Al₂O₃ thin film uniformly coats the Parylene C film, enhancing its physical barrier and chemical passivation under corrosive conditions. Full article

This study addresses the critical packaging requirements of implantable pressure sensors concerning measurement accuracy and environmental stability. We propose a solid/liquid composite packaging technique based on Parylene-C and silicone oil. Utilizing liquid silicone oil as an intermediate medium, this method effectively decouples solid/solid interface shear forces, thereby mitigating measurement errors caused by mechanical coupling. Furthermore, the superior hydrophobic properties of silicone oil and its defect-filling capability are employed to slow the infiltration rate of water molecules at the interface, ensuring long-term stability. The influence of the solid/liquid composite layer on the mechanical properties of the sensor’s sensitive element was analyzed through finite element simulation. The experimental results demonstrate the efficacy of this approach: after adding a liquid silicone oil layer between the Parylene coating and the sensitive element, the sensor’s accuracy improved to 0.5 mmHg within the pressure range encountered in clinical human applications. In simulated bodily fluids, it demonstrated exceptional long-term stability, with drift values consistently below 2 mmHg over a 30-day period. This research provides a feasible and straightforward solution for the packaging design of high-performance implantable pressure sensors. Full article

This study presents the development of a capacitive pressure sensor tailored for measuring the dynamic pressure of flow fields. The sensor is fabricated using the UMC 0.18 μm CMOS-MEMS process, incorporated with additional post-processing steps such as metal wet etching, supercritical CO₂ drying, and parylene encapsulation. The sensing architecture employs AD7746 as a capacitance-to-voltage converter (CVC), enabling the conversion of capacitance signals into voltage outputs for enhanced measurement fidelity. Structurally, the capacitive pressure sensor features a vacuum-sealed diaphragm capsule design with dual movable circular membranes functioning as sensing electrodes. A contact-mode capacitive configuration with a trapezoidal or Gong-like vacuum-chamber diaphragm is adopted to improve linearity and sensitivity. The output sensitivity was determined to be feasible for measuring dynamic pressure at 1–2 Pa resolution. Full article

The development of electro-thermal textiles has attracted growing interest as a promising approach for active thermal management in wearable systems. Metallic-coated fabrics can efficiently generate heat through the Joule effect; however, their long-term performance and safety are severely limited under perspiration due to metal ion release and corrosion. To overcome these challenges, this study introduces a Parylene-C encapsulation strategy for copper-coated polyethylene terephthalate nonwovens (CuPET) using a chemical vapor deposition (CVD) process. The conformal, biocompatible Parylene-C films (thickness 4–16 μm) act as effective protective barriers while preserving the porous textile structure. Morphological and comfort analyses demonstrate a controlled reduction in air permeability from 3100 to 1100 L·m⁻²·s⁻¹, maintaining acceptable breathability. Electro-thermal measurements reveal rapid and uniform heating, reaching 40–45 °C within 2 min at 2 V, and the addition of a thermal insulation layer further enhances the Joule heating efficiency, increasing the steady-state temperature by approximately 6 °C. ICP–OES results show an ≈80% reduction in copper ion release (from 28.34 mg·L⁻¹ to 5.80 mg·L⁻¹) after artificial sweat exposure. This work demonstrates a scalable encapsulation route that effectively balances sweat protection, electrical stability, and thermal performance, paving the way for safe, durable, and actively heated smart textiles for advanced thermal insulation applications. Full article

The integration of microstructured current collectors offers a potential pathway to enhance interface properties in solid-state battery architectures. In this work, we investigate the influence of surface morphology on the electrochemical performance of Zn/Na_2.99Ba_0.005OCl/Cu electrodeless pouch cells by fabricating copper thin films on microstructured parylene-C substrates using a combination of colloidal lithography and reactive ion etching. O₂ plasma etching times ranging from 0 to 15 min were used to tune the surface topography, resulting in a systematic increase in root-mean-square roughness and a surface area enhancement of up to ~30% for the longest etching duration, measured via AFM. Kelvin probe force microscopy-analyzed surface potential showed maximum differences of 270 mV between non-etched and 12-minute-etched Cu collectors. The results revealed that the chemical potential is the property that relates the surface of the Cu current collector/electrode with the cell’s ionic transport performance, including the bulk ionic conductivity, while four-point sheet resistance measurements confirmed that the copper layers’ resistivity maintained values close to those of bulk copper (1.96–4.5 µΩ.cm), which are in agreement with electronic mobilities (−6 and −18 cm²V⁻¹s⁻¹). Conversely, the charge carrier concentrations (−1.6 to −2.6 × 10²³ cm⁻³) are indirectly correlated with the performance of the cell, with the samples with lower CCC_bulk (fewer free electrons) performing better and showing higher maximum discharge currents, interfacial capacitance, and first-cycle discharge plateau voltage and capacity. The data were further consolidated with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. These results highlight that the correlation between the surface morphology and the cell is not straightforward, with the microstructured current collectors’ surface chemical potential and the charge carriers’ concentration being determinant in the performance of all-solid-state electrodeless sodium battery systems. Full article

Proton therapy has emerged as a highly precise and tissue-sparing radiotherapy technique, capitalizing on the unique energy deposition pattern of protons characterized by the Bragg peak. Ensuring treatment accuracy relies on calibration phantoms, often composed of tissue-equivalent polymeric materials. This study investigates the dosimetric behavior of four commonly used polymers—Parylene, Epoxy, Lexan, and Mylar—by analyzing their linear energy transfer (LET) values and Bragg curve characteristics across various proton energies. Experimental LET data were collected and used to train and evaluate the predictive power for Bragg peak of multiple artificial intelligence models, including kNN, SVR, MLP, RF, LWRF, XGBoost, 1D-CNN, LSTM, and BiLSTM. These algorithms were optimized using 10-fold cross-validation and assessed through statistical error and performance metrics including MAE, RAE, RMSE, RRSE, CC, and R². Results demonstrate that certain AI models, particularly RF and LWRF, accurately (in terms of all evaluation metrics) predict Bragg peaks in Epoxy polymers, reducing the reliance on costly and time-consuming simulations. In terms of CC and R² metrics, the LWRF model demonstrated superior performance, achieving scores of 0.9969 and 0.9938, respectively. However, when evaluated against MAE, RMSE, RAE, and RRSE metrics, the RF model emerged as the top performer, yielding values of 12.3161, 15.8223, 10.3536, and 11.4389, in the same order. Additionally, the SVR model achieved the highest number of statistically significant differences when compared pairwise with the other eight models, showing significance against six of them. The findings support the use of AI as a robust tool for designing reliable calibration phantoms and optimizing proton therapy planning. This integrative approach enhances the synergy between materials science, medical physics, and data-driven modeling in advanced radiotherapy systems. Full article

This study presents a comprehensive evaluation and an equivalent circuit modeling of the skin–electrode impedance characteristics of three types of ultra-thin tattoo electrodes, all based on Parylene C nanofilms but with different active materials: Gold, Silver, and PEDOT:PSS. Their performance was compared to standard disposable Ag/AgCl electrodes. Impedance measurements were carried out on six human subjects under controlled conditions, assessing the frequency response in the range of 20 Hz to 1 kHz. For each subject, the impedance was recorded six times over one hour to investigate the stability and the temporal performance. The collected data were subsequently analyzed to model the electrical properties and interface behavior of each electrode type. The findings demonstrate that the tattoo electrodes offer impedance levels comparable to those of Ag/AgCl electrodes (in the order of tens of kΩ at 20 Hz), while providing additional benefits such as enhanced conformability, improved skin adhesion, and reduced skin irritation during use. Furthermore, the modeling of the skin–electrode interface through a more detailed equivalent circuit than the single time constant model enables a more detailed interface analysis and description, with fitting algorithm R² scores of about 0.999 and 0.979 for the impedance magnitude and impedance phase, respectively. The proposed equivalent circuit offers valuable insights for optimizing electrode design, supporting the potential of Parylene C-based tattoo electrodes as promising alternatives for next-generation wearable bioelectronic applications. Full article

The motivation of this work is to enable the use of piezoelectric micromachined ultrasonic transducer (PMUT)-based implants within the human body for biomedical applications, particularly for power and data transfer for implanted medical devices. To protect surrounding tissue and ensure PMUT functionality over time, biocompatible and hermetic encapsulation is essential. This study investigates the impact of Parylene F-VT4 layers of various thicknesses as well as the effect of multilayer stacks of Parylene F-VT4 combined with atomic layer-deposited nanolayers of Al₂O₃ and HfO₂ on the mechanical and acoustic properties of PMUTs. PMUTs with various diameters (40 µm, 60 µm, and 80 µm) are fabricated and tested both as stand-alone devices and as arrays. The mechanical behavior of single stand-alone PMUT devices is characterized in air and in water using laser Doppler vibrometry (LDV), while the acoustic output of arrays is evaluated by pressure measurements in water. Experimental results reveal a non-monotonic change in resonance frequency as a function of increasing encapsulation thickness due to the competing effects of added mass and increased stiffness. The performance of PMUT arrays is clearly influenced by the encapsulation. For certain array designs, the encapsulation significantly improved the arrays’ pressure output, a change that is attributed to the change in the acoustic wavelength and inter-element coupling. These findings highlight the impact of encapsulation in modifying and potentially enhancing PMUT performance. Full article

In this paper, a novel through-silicon via (TSV) fabrication strategy based on through-hole structures is proposed for low-cost and low-complexity manufacturing. Compared to conventional TSV fabrication processes, this method significantly simplifies the process flow by employing double-sided liner deposition, double-sided barrier layer/seed layer formation, and double-sided Cu electroplating. This method enhances the TSV stability by eliminating Cu contamination issues during chemical–mechanical polishing (CMP), which are a common challenge in traditional blind via fabrication processes. Additionally, the liner and barrier layer/seed layer achieve a high step coverage exceeding 80%, ensuring excellent conformality and structural integrity. For electroplating, a multi-stage bi-directional electroplating technique is introduced to enable void-free Cu filling in TSVs. The fabricated TSVs exhibit an ultra-low leakage current of 135 fA at 20 V, demonstrating their potential for advancing 3D integration technologies in heterogeneous integration. Full article

This work presents a novel microfabrication process that addresses the interference of thiol groups on off-stoichiometry thiolene (OSTE) surfaces with the curing of polydimethylsiloxane (PDMS) by integrating the high-performance polymer Parylene-C. The process utilizes a Parylene-C coating to encapsulate the active thiol groups on the OSTE surface, enabling precise replication of PDMS microstructures. Based on this method, PDMS micropillar arrays and microwell arrays were successfully fabricated and applied in passive plasma separation and polymorphic crystal formation, respectively. The experimental results demonstrate that the plasma-separation chip efficiently isolates plasma from whole-blood samples with varying hematocrit (HCT) levels, achieving a separation efficiency of up to 57.5%. Additionally, the microwell array chip exhibits excellent stability and controllability in the growth of salt and protein crystals. This study not only provides a new approach for microfabricating microfluidic chips, but also highlights its potential applications in biomedical diagnostics and materials science. Full article

This study comprehensively examines the barrier properties, aging behavior, and failure mechanisms of Parylene F-VT4 films, applied at four distinct thicknesses (0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm), as encapsulation layers for implantable medical devices. Parylene F-VT4, a fluorinated polymer known for its mechanical flexibility, thermal stability, and chemical inertness, is a promising candidate for long-term hermetic encapsulation. Parylene F-VT4 was uniformly deposited via a dedicated chemical vapor deposition (CVD) process typically used for Parylene depositions. The investigation of the Parylene F-VT4 films included pinhole density characterization, electrochemical impedance spectroscopy (EIS), and testing of coating lifetime based on the resistance of Cu meanders protected by Parylene F-VT4 when immersed in phosphate-buffered saline (PBS) under accelerated aging conditions (PBS at 60 °C) over 550 days. The EIS results demonstrated that thicker coatings (1.2 µm) exhibited excellent barrier properties and resistance to electrolyte penetration, whereas thinner coatings (0.3 µm and 0.6 µm) showed more rapid degradation due to microvoids and pinholes. The temporal evaluation of EIS spectra highlighted the gradual decrease in impedance magnitude, indicating the ingress of ions and water into the coating. The lifetime in PBS at 60 °C was determined by resistance-based lifetime measurements on Cu meander structures coated with Parylene F-VT4 coatings. The lifetime at 37 °C was calculated, assuming an acceleration factor of 2 per 10 °C increase in temperature, yielding lifetimes of approximately 25 days, 6.4 months, 2.3 years, and 4.5 years for 0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm coatings, respectively. These findings highlight the critical relationship between thickness and durability, providing valuable insights into the long-term performance of thin Parylene F-VT4 films for implantable devices. Full article