Biocompatibility and biofouling of MEMS drug delivery devices

Recent advances in electrodes for noninvasive recording of electroencephalograms expand opportunities collecting such data for diagnosis of neurological disorders and brain-computer interfaces. Existing technologies, however, cannot be used effectively in continuous, uninterrupted modes for more than a few days due to irritation and irreversible degradation in the electrical and mechanical properties of the skin interface. Here we introduce a soft, foldable collection of electrodes in open, fractal mesh geometries that can mount directly and chronically on the complex surface topology of the auricle and the mastoid, to provide highfidelity and long-term capture of electroencephalograms in ways that avoid any significant thermal, electrical, or mechanical loading of the skin. Experimental and computational studies establish the fundamental aspects of the bending and stretching mechanics that enable this type of intimate integration on the highly irregular and textured surfaces of the auricle. Cell level tests and thermal imaging studies establish the biocompatibility and wearability of such systems, with examples of high-quality measurements over periods of 2 wk with devices that remain mounted throughout daily activities including vigorous exercise, swimming, sleeping, and bathing. Demonstrations include a text speller with a steadystate visually evoked potential-based brain-computer interface and elicitation of an event-related potential (P300 wave).or more than 80 y, electroencephalography (EEG) has provided an effective noninvasive means to study human brain activity (1). EEG is instrumental in a wide range of clinical and research applications, from diagnosing epilepsy (2) to improving our understanding of language comprehension (3) and the development of brain-computer interfaces (BCI) (4). Conventional EEG recording systems, particularly the physical interface between the sensor (commonly known as an electrode) and the head, have limitations that constrain the more widespread use of EEG monitoring. Electrodes typically consist of rigid metal disks mechanically secured to the head with a mesh cap and chin strap, where electrolyte gels (5) enable efficient electrical coupling by reducing the impedance at the skin interface. This arrangement causes skin irritation (erythema) and leads to electrical degradation for periods of use that extend more than a few hours, typically caused by drying of the electrolyte gel (6). Recent technologies replace the gel (7, 8) with needles (8, 9), contact probes (10, 11), capacitive disks (12, 13), conductive composites (14, 15), or nanowires (16). Such dry electrodes have some promise, but they require multistep preparations, obtrusive wiring interfaces, and/or cumbersome mechanical fixtures. These shortcomings limit the potential for long-term use in diagnosis of neurological disabilities (17, 18) or in persistent BCI (17,19). For example, although microneedle electrodes can record EEG signals for a few hours (20), the interface does not offer the robustness, comfort, or eas...

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“…The epidermal electrode incorporates well-characterized, biocompatible materials [silicone (25), gold (33), and polyimide (34)]. …”

Section: Resultsmentioning

confidence: 99%

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

Norton

Lee

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

317

283

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“…Studies have shown that the concentration of silanol groups (Si-OH) and the degree of their ionization define the hydrophobicity of silicon dioxide (silica) surfaces and govern their adsorption properties and thus also, the behavior of silica-based materials in processes such as biomolecular adhesion and biomineralization (Sumper & Brunner, 2008;Voskerician et al 2003). In computational studies of protein-oxide surface interactions, ionization may be represented explicitly (Friedrichs et al 2013;Köppen & Langel, 2010;Patwardhan et al 2012;Tosaka et al 2010), or by assigning uniform partial charges to selected surface atoms (Kubiak-Ossowska & Mulheran, 2012).…”

Section: Ionization and Hydrationmentioning

confidence: 99%

Modeling and simulation of protein–surface interactions: achievements and challenges

Ozboyaci

Kokh

Corni

et al. 2016

Quart. Rev. Biophys.

191

199

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Abstract. Understanding protein-inorganic surface interactions is central to the rational design of new tools in biomaterial sciences, nanobiotechnology and nanomedicine. Although a significant amount of experimental research on protein adsorption onto solid substrates has been reported, many aspects of the recognition and interaction mechanisms of biomolecules and inorganic surfaces are still unclear. Theoretical modeling and simulations provide complementary approaches for experimental studies, and they have been applied for exploring protein-surface binding mechanisms, the determinants of binding specificity towards different surfaces, as well as the thermodynamics and kinetics of adsorption. Although the general computational approaches employed to study the dynamics of proteins and materials are similar, the models and force-fields (FFs) used for describing the physical properties and interactions of material surfaces and biological molecules differ. In particular, FF and water models designed for use in biomolecular simulations are often not directly transferable to surface simulations and vice versa. The adsorption events span a wide range of time-and length-scales that vary from nanoseconds to days, and from nanometers to micrometers, respectively, rendering the use of multi-scale approaches unavoidable. Further, changes in the atomic structure of material surfaces that can lead to surface reconstruction, and in the structure of proteins that can result in complete denaturation of the adsorbed molecules, can create many intermediate structural and energetic states that complicate sampling. In this review, we address the challenges posed to theoretical and computational methods in achieving accurate descriptions of the physical, chemical and mechanical properties of protein-surface systems. In this context, we discuss the applicability of different modeling and simulation techniques ranging from quantum mechanics through all-atom molecular mechanics to coarse-grained approaches. We examine uses of different sampling methods, as well as free energy calculations. Furthermore, we review computational studies of protein-surface interactions and discuss the successes and limitations of current approaches.

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“…Moreover, Ref. 11 shows that SU8 is a good biocompatible material. These properties make SU8 a suitable material for electrothermal microactuators, especially for building tools for biomedical research.…”

Section: Designmentioning

confidence: 99%

Integrated Silicon-Polymer Laterally Stacked Bender for Sensing Microgrippers

Due

Wei

Sarro

et al. 2006

2006 5th IEEE Conference on Sensors

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-This paper presents a novel electro-thermal microgripper based on integrated silicon-polymer laterally stacked microactuators. The device consists of a serpentineshape deep silicon structure with a thin film aluminum heater on the top and filling polymer in the trenches among the vertical silicon parts. The fabrication is based on deep reactive ion etching of silicon, aluminum sputtering and SU8 filling. The actuator is 500 pm long, 65 pm wide and 50 pm high. The microgripper generates a large motion up to 52 pm at a driving voltage of only 2 V and with a power consumption of 50 mW. The maximum working temperature is 164°C at 2 V.

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Biocompatibility and biofouling of MEMS drug delivery devices

Cited by 492 publications

References 21 publications

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

Modeling and simulation of protein–surface interactions: achievements and challenges

Integrated Silicon-Polymer Laterally Stacked Bender for Sensing Microgrippers

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