Plasma removal of Parylene C

Parylene C, an emerging material in microelectromechanical systems, is of particular interest in biomedical and lab-on-a-chip applications where stable, chemically inert surfaces are desired. Practical implementation of Parylene C as a structural material requires the development of micropatterning techniques for its selective removal. Dry etching methods are currently the most suitable for batch processing of Parylene structures. A performance comparison of three different modes of Parylene C plasma etching was conducted using oxygen as the primary reactive species. Plasma, reactive ion and deep reactive ion etching techniques were explored. In addition, a new switched chemistry process with alternating cycles of fluoropolymer deposition and oxygen plasma etching was examined to produce structures with vertical sidewalls. Vertical etch rates, lateral etch rates, anisotropy and sidewall angles were characterized for each of the methods. This detailed characterization was enabled by the application of replica casting to obtain cross sections of etched structures in a non-destructive manner. Application of the developed etch recipes to the fabrication of complex Parylene C microstructures is also discussed

Multi-fuel rotary engine for general aviation aircraft

Design studies of advanced multifuel general aviation and commuter aircraft rotary stratified charge engines are summarized. Conceptual design studies were performed at two levels of technology, on advanced general aviation engines sized to provide 186/250 shaft kW/hp under cruise conditions at 7620 (25000 m/ft) altitude. A follow on study extended the results to larger (2500 hp max.) engine sizes suitable for applications such as commuter transports and helicopters. The study engine designs were derived from relevant engine development background including both prior and recent engine test results using direct injected unthrottled rotary engine technology. Aircraft studies, using these resultant growth engines, define anticipated system effects of the performance and power density improvements for both single engine and twin engine airplanes. The calculated results indicate superior system performance and 27 to 33 percent fuel economy improvement for the rotary engine airplanes as compared to equivalent airframe concept designs with current baseline engines. The research and technology activities required to attain the projected engine performance levels are also discussed

Biocompatible parylene neurocages developing a robust method for live neural network studies

We present a refined method and design for fabricating parylene neurocages for in vitro studies of live neural networks. Parylene neurocages are biocompatible and very robust, making them ideally suited for studying the synaptic connections netween individual neurons to gain insight into learning and memory. The neurocage fabrication process is significantly less complex than earlier versions. Previous neurocage designs achieved limited neuronal outgrowth; however, the long-term cell survival rate was 50%

Development of biocompatible parylene neurocages

We present a refined method and design for building parylene neurocages for in vitro studies of live neural networks. Parylene neurocages are biocompatible and very robust, making them ideally suited for studying the synaptic connections between individual neurons to gain insight into learning and memory. The neurocage fabrication process is significantly less complex than earlier versions. Previous neurocage designs achieved limited neuronal outgrowth; however, the long-term cell survival rate was 50%

A parylene MEMS flow sensing array

We have demonstrated the first parylene MEMS thermal sensor array capable of detecting small flows down to 0.5 µl/min. The device is fabricated using low-temperature parylene/platinum technology and consists of metallic sensors suspended on a membrane over a bulk micromachined silicon channel. For the first time, insightful results from three different methods of flow sensing using a single device are studied and compared. Multi-mode testing using hot film, calorimetric, and time-of-flight techniques at low overheat ratios has been performed. Thus, this device is biocompatible in both construction and operation

Parylene etching techniques for microfluidics and bioMEMS

Parylene C (poly(monochloro-p-xylylene)) is a member of a unique family of thermoplastic, crystalline polymers. Compared to other polymers, parylene films are exceptionally conformal and chemically inert owing to its vapor deposition polymerization (VDP) coating process. These properties bring about many interesting possibilities for MEMS, particularly in microfluidic and bioMEMS applications. Dry etching techniques are required to define fine features in parylene films. For the first time, selective parylene C removal using oxygen-based plasmas is characterized for plasma etching, reactive ion etching (RIE), and deep reactive ion etching (DRIE) based methods. The ability of these techniques to achieve high aspect ratio (HAR) structures desirable for MEMS applications is also investigated

Implantable Unpowered Parylene MEMS Intraocular Pressure Sensor

This paper presents the first implantable, unpowered, parylene-based micro-electro-mechanical-systems (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant structures, this sensor registers pressure variations without power consumption/transduction. Micromachined high-aspect-ratio thin-walled tubes in different geometric layouts are exploited to obtain a high-sensitivity pressure response. An integrated packaging method has been successfully developed to realize suture-less implantation of the device. In vitro testing results have demonstrated that the IOP sensor can achieve 0.67 degree/mmHg angular sensitivity with a spiral-tube design, 3.43 µm/mmHg lateral sensitivity with a long-armed-tube design, and 0.38 µm/mmHg longitudinal sensitivity with a serpentine-tube design. This IOP sensor is designed to be implanted in the anterior chamber of the eye and anchored directly on the iris so that, under incident visible light, the pressure response of the implant can be directly observed from outside the eye, which enables faithful and unpowered IOP monitoring in glaucoma patient

Wafer-Level Parylene Packaging With Integrated RF Electronics for Wireless Retinal Prostheses

This paper presents an embedded chip integration technology that incorporates silicon housings and flexible Parylene-based microelectromechanical systems (MEMS) devices. Accelerated-lifetime soak testing is performed in saline at elevated temperatures to study the packaging performance of Parylene C thin films. Experimental results show that the silicon chip under test is well protected by Parylene, and the lifetime of Parylenecoated metal at body temperature (37°C) is more than 60 years, indicating that Parylene C is an excellent structural and packaging material for biomedical applications. To demonstrate the proposed packaging technology, a flexible MEMS radio-frequency (RF) coil has been integrated with an RF identification (RFID) circuit die. The coil has an inductance of 16 μH with two layers of metal completely encapsulated in Parylene C, which is microfabricated using a Parylene–metal–Parylene thin-film technology. The chip is a commercially available read-only RFID chip with a typical operating frequency of 125 kHz. The functionality of the embedded chip has been tested using an RFID reader module in both air and saline, demonstrating successful power and data transmission through the MEMS coil

The cost-effectiveness of nivolumab monotherapy for the treatment of advanced melanoma patients in England

Background: Nivolumab was the first programmed death receptor 1 (PD-1) immune checkpoint inhibitor to demonstrate long-term survival benefit in a clinical trial setting for advanced melanoma patients. Objective: To evaluate the cost effectiveness of nivolumab monotherapy for the treatment of advanced melanoma patients in England. Methods: A Markov state-transition model was developed to estimate the lifetime costs and benefits of nivolumab versus ipilimumab and dacarbazine for BRAF mutation-negative patients and versus ipilimumab, dabrafenib, and vemurafenib for BRAF mutation-positive patients. Covariate-adjusted parametric curves for time to progression, pre-progression survival, and post-progression survival were fitted based on patient-level data from two trials and long-term ipilimumab survival data. Indirect treatment comparisons between nivolumab, ipilimumab, and dacarbazine were informed by these covariate-adjusted parametric curves, controlling for differences in patient characteristics. Kaplan–Meier data from the literature were digitised and used to fit progression-free and overall survival curves for dabrafenib and vemurafenib. Patient utilities and resource use data were based on trial data or the literature. Patients are assumed to receive nivolumab until there is no further clinical benefit, assumed to be the first of progressive disease, unacceptable toxicity, or 2 years of treatment. Results: Nivolumab is the most cost-effective treatment option in BRAF mutation-negative and mutation-positive patients, with incremental cost-effectiveness ratios of £24,483 and £17,362 per quality-adjusted life year, respectively. The model results are most sensitive to assumptions regarding treatment duration for nivolumab and the parameters of the fitted parametric survival curves. Conclusions: Nivolumab is a cost-effective treatment for advanced melanoma patients in England

Implantable micromechanical parylene-based pressure sensors for unpowered intraocular pressure sensing

This paper presents the first implantable, unpowered, parylene-based microelectromechanical system (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant spiral-tube structures, this sensor registers pressure variations without electrical or powered signal transduction of any kind. Micromachined high-aspect-ratio polymeric hollow tubes with different geometric layouts are implemented to obtain high-sensitivity pressure responses. An integrated device packaging method has been developed toward enabling minimally invasive suture-less needle-based implantation of the device. Both in vitro and ex vivo device characterizations have successfully demonstrated mmHg resolution of the pressure responses. In vivo animal experiments have also been conducted to verify the biocompatibility and functionality of the implant fixation method inside the eye. Using the proposed implantation scheme, the pressure response of the implant can be directly observed from outside the eye under visible light, with the goal of realizing convenient, direct and faithful IOP monitoring in glaucoma patients