3D MEA Research Articles

Modeling computer sight based on DEM data to detect terrain breaks caused by gully erosion on the loess Plateau

As a type of terrain break, the gully shoulder line is of great significance to locate the scope of surface failure and soil erosion. Based on the knowledge of the terrain structure of loess gullies, this paper modeled sight lines to calculate the three-dimensional maximum elevation angle (3D MEA). Then, a critical MEA value of 35° was determined via human vision to extract negative terrain and shoulder lines considering unmanned aerial vehicle (UAV)- and light detection and ranging (lidar)-based digital elevation models (DEMs). In addition to the DEM resolution, the uncertainties caused by the direction number, look distance and skip radius of computer sight were further examined. It was suggested that the process should involve observing at least 12 directions to detect complete information on terrain breaks. The simulation process required a relatively large look distance to analyze global terrain changes because a small distance could limit sight within the local window. The skip radius could result in the process ignoring nearby abrupt changes in terrain, thus causing negative terrain to be misclassified as positive terrain near shoulder lines. The concept of wall morphology was introduced to attribute the critical value to the repose angle of loess gullies. Eventually, the MEA was compared with many other parameters. It could be concluded that the slope is limited to the local scale, while the MEA could combine local and global scales using a large look distance. The hillshade is limited to one viewing direction, but the 3D MEA is a comprehensive layered index from multiple directions. This study is a novel exploration of interdisciplinary hydraulic engineering and information technology. This approach reduces terrain breaks from three-dimensional space into a one-dimensional index and simplifies shoulder lines as a critical 3D MEA value related to loess material properties. This research could be adopted for soil and water conservation.

Spatiotemporal analysis of 3D human iPSC-derived neural networks using a 3D multi-electrode array.

While there is a growing appreciation of three-dimensional (3D) neural tissues (i.e., hydrogel-based, organoids, and spheroids), shown to improve cellular health and network activity to mirror brain-like activity in vivo, functional assessment using current electrophysiology techniques (e.g., planar multi-electrode arrays or patch clamp) has been technically challenging and limited to surface measurements at the bottom or top of the 3D tissue. As next-generation MEAs, specifically 3D MEAs, are being developed to increase the spatial precision across all three dimensions (X, Y, Z), development of improved computational analytical tools to discern region-specific changes within the Z dimension of the 3D tissue is needed. In the present study, we introduce a novel computational analytical pipeline to analyze 3D neural network activity recorded from a "bottom-up" 3D MEA integrated with a 3D hydrogel-based tissue containing human iPSC-derived neurons and primary astrocytes. Over a period of ~6.5 weeks, we describe the development and maturation of 3D neural activity (i.e., features of spiking and bursting activity) within cross sections of the 3D tissue, based on the vertical position of the electrode on the 3D MEA probe, in addition to network activity (identified using synchrony analysis) within and between cross sections. Then, using the sequential addition of postsynaptic receptor antagonists, bicuculline (BIC), 2-amino-5-phosphonovaleric acid (AP-5), and 6-cyano-5-nitroquinoxaline-2,3-dione (CNQX), we demonstrate that networks within and between cross sections of the 3D hydrogel-based tissue show a preference for GABA and/or glutamate synaptic transmission, suggesting differences in the network composition throughout the neural tissue. The ability to monitor the functional dynamics of the entire 3D reconstructed neural tissue is a critical bottleneck; here we demonstrate a computational pipeline that can be implemented in studies to better interpret network activity within an engineered 3D neural tissue and have a better understanding of the modeled organ tissue.

Fully Integrated 3D Microelectrode Arrays with Polydopamine-Mediated Silicon Dioxide Insulation for Electrophysiological Interrogation of a Novel 3D Human, Neural Microphysiological Construct.

Advances within in vitro biological system complexity have enabled new possibilities for the "Organs-on-a-Chip" field. Microphysiological systems (MPS) as such incorporate sophisticated biological constructs with custom biological sensors. For microelectromechanical systems (MEMS) sensors, the dielectric layer is critical for device performance, where silicon dioxide (SiO2) represents an excellent candidate due to its biocompatibility and wide utility in MEMS devices. Yet, high temperatures traditionally preclude SiO2 from incorporation in polymer-based BioMEMS. Electron-beam deposition of SiO2 may provide a low-temperature, dielectric serving as a nanoporous MPS growth substrate. Herein, we enable improved adherence of nanoporous SiO2 to polycarbonate (PC) and 316L stainless steel (SS) via polydopamine (PDA)-mediated chemistry. The resulting stability of the combinatorial PDA-SiO2 film was interrogated, along with the nature of the intrafilm interactions. A custom polymer-metal three-dimensional (3D) microelectrode array (3D MEA) is then reported utilizing PDA-SiO2 insulation, for definition of novel dorsal root ganglion (DRG)/nociceptor and dorsal horn (DH) 3D neural constructs in excess of 6 months for the first time. Spontaneous/evoked compound action potentials (CAPs) are successfully reported. Finally, inhibitory drugs treatments showcase pharmacological responsiveness of the reported multipart biological activity. These results represent the initiation of a novel 3D MEA-integrated, 3D neural MPS for the long-term electrophysiological study.

A three-dimensional micro-electrode array for in-vitro neuronal interfacing

Objective. In this paper, we report on the development of an easy-to-fabricate three-dimensional Micro-Electrode Array (3D-MEA) specifically designed for brain-on-a-dish applications. Approach. The proposed device consists of pillar-shaped gold microelectrodes realized by electroplating directly on top of a standard MEA, making this approach highly versatile and convenient for batch fabrication. Moreover, with this simple technique, it is possible to obtain electrodes with a height of more than 100 µm onto different kind of substrates, ranging from glass to flexible plastic ones. Main results. This novel 3D-MEA structure has been validated with acute brain slices, successfully recording both epileptiform-like discharges (upon the administration of 4-AP), and electrically-evoked neuronal activity. The preliminary validation showed a substantial improvement in the signals amplitude with respect to both commercial and custom planar electrodes thanks to a better coupling offered by the peculiar shape of the three-dimensional electrodes. Significance. Beside the versatility of the fabrication approach, which allows to obtain 3D MEA devices onto both rigid and flexible substrates, the reported validation showed how the pillar approach can outperform standard planar MEA recordings in terms of signal amplitude. Moreover, thanks to the possibility of obtaining multi-level 3D structures within the same device, the proposed fabrication technique offers an interesting and flexible approach for the development of a new family of electrophysiological tools for 3D in vitro electrophysiology, in particular for acute brain slices and 3D neuronal cultures for brain-on-a-dish applications.

Makerspace microfabrication of a stainless steel 3D microneedle electrode array (3D MEA) on a glass substrate for simultaneous optical and electrical probing of electrogenic cells.

Microfabrication and assembly of a Three-Dimensional Microneedle Electrode Array (3D MEA) based on a glass-stainless steel platform is demonstrated involving the utilization of non-traditional “Makerspace Microfabrication” techniques featuring cost-effective, rapid fabrication and an assorted biocompatible material palette. The stainless steel microneedle electrode array was realized by planar laser micromachining and out-of-plane transitioning to have a 3D configuration with perpendicular transition angles. The 3D MEA chip is bonded onto a glass die with metal traces routed to the periphery of the chip for electrical interfacing. Confined precision drop casting (CPDC) of PDMS is used to define an insulation layer and realize the 3D microelectrodes. The use of glass as a substrate offers optical clarity allowing for simultaneous optical and electrical probing of electrogenic cells. Additionally, an interconnect using 3D printing and conductive ink casting has been developed which allows metal traces on the glass chip to be transitioned to the bottomside of the device for interfacing with commercial data acquisition/analysis equipment. The 3D MEAs demonstrate an average impedance/phase of ∼13.3 kΩ/−12.1° at 1 kHz respectively, and an average 4.2 μV noise. Lastly, electrophysiological activity from an immortal cardiomyocyte cell line was recorded using the 3D MEA demonstrating end to end device development.

Bioelectronics: Ultrasoft Silicone Gel as a Biomimetic Passivation Layer in Inkjet‐Printed 3D MEA Devices (Adv. Biosys. 9/2019)

In article number 1900130, Hideaki Yamamoto and co-workers describe a novel multielectrode (MEA) array device with a biomimetic, ultrasoft interface. Here, inkjet printing is used to fabricate 3D MEA structures, which are then passivated with a polydimethylsiloxane gel. Primary cortical neurons are grown on the device, and effective stimulation of the culture confirms functional cell-device coupling.

Fabrication and Characterization of a 3D Printed, MicroElectrodes Platform With Functionalized Electrospun Nano-Scaffolds and Spin Coated 3D Insulation Towards Multi- Functional Biosystems

We demonstrate new fabrication technologies for 3D microelectrode platforms, fully realized for several 3D multi-functional biosystems. The microfabrication technology involves 3D metallized microtowers realized by 3D printing, metal evaporation, and coarse biocompatible lamination to insulate the traces. Electrospun 3D nanofiber scaffolds (NFSs) are coupled to the microelectrodes to provide additional functionality. The scaffolds were formed via electrospinning two types of nanofibers: ~200-500 nm PET, a hydrophobic polymer, and ~100 nm PVA/PAA, a hydrophilic co-polymer. PVA/PAA nanofibers had consistent diameters without beading and were used in subsequent experiments. Impedance measurements before, 651.3 $\text{k}\Omega $ , and after, 659.4 $\text{k}\Omega $ , deposition of PVA/PAA remains unchanged, indicating enhanced functionality without interfering with the electrical characteristics of the 3D MEAs. Silver nanoparticles (Ag NP) were embedded as model drug compounds in the PVA/PAA-NFS to demonstrate the potential of the 3D MEA as a biosensor and drug delivery system. TEM and antimicrobial studies demonstrated ~5-15 nm Ag NP within the PVA/PAA-NFS, which was potent to Acinetobacter baumannii and Escherichia coli. Fine 3D insulation atop the microtowers is achieved using a drop-casted/spin-coated 3D layer of Polystyrene (PS), which is laser micromachined to realize $50\times 50\,\,\mu \text{m}^{{2}}\,\,3\text{D}$ microelectrodes with impedance properties similar to other reported approaches. [2019-0043]

Functionalized Thick Film Impedance Sensors for Use in In Vitro Cell Culture.

Multi-electrode arrays find application in electrophysiological recordings. The quality of the captured signals depends on the interfacial contact between electrogenic cells and the electronic system. Therefore, it requires reliable low-impedance electrodes. Low-temperature cofired ceramic technology offers a suitable platform for rapid prototyping of biological reactors and can provide both stable fluid supply and integrated bio-hardware interfaces for recordings in electrogenic cell cultures. The 3D assembly of thick film gold electrodes in in vitro bio-reactors has been demonstrated for neuronal recordings. However, especially when dimensions become small, their performance varies strongly. This work investigates the influence of different coatings on thick film gold electrodes with regard to their influence on impedance behavior. PEDOT:PSS layer, titanium oxynitride and laminin coatings are deposited on LTCC gold electrodes using different 2D and 3D MEA chip designs. Their impedance characteristics are compared and discussed. Titanium oxynitride layers emerged as suitable functionalization. Small 86-µm-electrodes have a serial resistance Rs of 32 kOhm and serial capacitance Cs of 4.1 pF at 1 kHz. Thick film gold electrodes with such coatings are thus qualified for signal recording in 3-dimensional in vitro cell cultures.

Batch Fabrication of Three-Dimensional Microelectrode Arrays For The In-Vitro Investigation Of Tissue Slices And 3D Cell Cultures

Event Abstract Back to Event Batch Fabrication of Three-Dimensional Microelectrode Arrays For The In-Vitro Investigation Of Tissue Slices And 3D Cell Cultures Manuel Martina1, Stefan Klaus2, Alfred Stett3, Thoralf Herrmann4, Günther Zeck5 and Claus Burkhardt6* 1 NMI Natural and Medical Sciences Institute at the University Tubingen, Microsystems / Nanotechnology, Germany 2 NMI Naturwissenschaftliches und Medizinisches Institut, Microsystems / Nanotechnology, Germany 3 NMI Natural and Medical Sciences Institute at the University Tubingen, Technical Engineering & Biophysics, Germany 4 NMI Naturwissenschaftliches und Medizinisches Institut, Neurochip Research, Germany 5 NMI at the University Tuebingen, Neurochip Research, Germany 6 NMI Natural and Medical Sciences Institute at the University Tubingen, Microsystems / Nanotechnology, Germany Motivation Three dimensional microelectrode arrays pose a valuable tool for the in-vitro investigation of acute tissue slices [1,2]. The reason for this is a dead-cell layer, which occurs due to the preparation of tissue slices and dampens the electrical signal when using planar electrodes. 3D MEAs can overcome the dead-cell layer by penetrating the tissue and moving the active electrode array in direct proximity to the living cells. Furthermore, three dimensional cell cultures become an increasingly hot topic and are subject of more and more investigations [3,4]. Here, a 3D MEA can be applied to measure signals, preferable in different defined heights from the MEA surface. A microelectrode array combining planar and 3D electrodes, with heights ranging from some ten micrometers to a hundred micrometer, can be a valuable tool to progress in this field of research. Here, we present a batch fabrication process, which allows to combine planar electrodes and 3D electrodes with tunable geometry. Material and Methods A process scheme of the fabrication is depicted in Figure 1. First, a silicon-on-glass wafer (consisting of a 50 µm thick silicon layer bonded to a thick glass wafer) is coated with a 50 nm thick silicon nitride layer. The silicon nitride layer is structured by optical lithography into square masks, where the electrode tips will be located. The mask size correlates to the later tip height. After anisotropic etching in potassium hydroxide, the majority of the silicon is removed, yielding a transparent substrate with 3D silicon structures. From here, structuring into a MEA is done by standard processes. During the final step, namely the deposition of the electrode material, height and size of the active electrode area is determined. Results and Discussion Following the developed process, an electrode array with 50 µm high tips is fabricated. Figure 2 shows SEM images of the finished 3D electrodes. The active electrode area, consisting of a fractal titanium nitride layer is located at the upper 20 µm, respectively 15 µm. The aspect ratio (tip height / base diameter) of the structures is measured to 2 and given by the silicon crystal orientation and mask shape. The apex angle is measured to 28°, with a tip radius of 1 µm. This geometry should be well suited for tissue penetration. The developed process possess several advantages over already reported ways to fabricate 3D MEAs, e.g. the isotropic wet etching of glass or the dry etching of SU-8 resist for structure fabrication. Structures fabricated using a silicon-on-glass wafer are completely chemically inert in organic solvents (which are used in lithography processes), mechanically stable during fabrication as well as in application and provide an aspect ratio which cannot be achieved by isotropic wet etching. Conclusions and Outlook We developed a stable and batch process compatible way to fabricate MEAs with 3D electrodes. Although the electrode aspect ratio is fixed, tip height, tip distance and the size of the active electrode area can be tuned to one’s needs. The fabrication of these MEAs utilizes parallel processing and allows to produce these substrate in high numbers to affordable prices. Electrophysiological measurements with these MEAs are currently conducted. In the future, tip geometry and aspect ratio can be further tuned by adapting the mask shape. With proper mask geometry and orientation, triangular tips with apex angles below 25° (known from AFM probes) can be fabricated. It might be possible to fabricate tips with heights of 100 µm and more by using a silicon-on-glass wafer with a thicker silicon layer. Figure Legend Figure 1: Process scheme for the fabrication of an electrode array, combining planar electrodes and 3D electrodes of different heights. Figure 2: SEM images of 50 µm high tips with different sized active electrode areas (red).

LTCC Based Multi-Electrode Arrays for In-Vitro Cell Culture

Neurobiological concepts based on state-of-the art technology have so far lacked the complexity of actual high-level neurobiological systems. Two key advances are needed to improve our understanding of such systems: in vitro 3D-neuronal cell culture and 3D MEA systems for measuring such 3D-cultures. These requirements call for smart multilayer and packaging technology. The material Green Tape TM from DuPont Nemours is chosen for the presented works, because its compatibility and those of available metallisation with cell cultures is already proven. An LTCC multilayer circuit with gold electrodes is the base of the 3D MEA. The layout of the 3D MEA is designed to fit the MEA2100-System for in vitro recording from Multi Channel Systems and enable thus a comparable data processing to established 2D MEAs Slots. The surface topography of the thick film electrodes and the surface state is investigated with laser scanning microscopy, SEM, XPS and measurements of the wetting angle of contact. The impedance of the screen printed electrodes is discussed taking these data into account. Their impedance amounts to 24 kΩ and are falls thus below the impedance of commercially available electroplated gold electrodes of 30 kΩ. First promising results have been achieved using 3D MEAs for 2D culture of human pluripotent stem cell derived neural cells.

Micromachined three-dimensional electrode arrays for transcutaneous nerve tracking

We report the development of metal transfer micromolded (MTM) three-dimensional microelectrode arrays (3D MEAs) for a transcutaneous nerve tracking application. The measurements of electrode–skin–electrode impedance (ESEI), electromyography (EMG) and nerve conduction utilizing these minimally invasive 3D MEAs are demonstrated in this paper. The 3D MEAs used in these measurements consist of a metalized micro-tower array that can penetrate the outer layers of the skin in a painless fashion and are fabricated using MTM technology. Two techniques, an inclined UV lithography approach and a double-side exposure of thick negative tone resist, have been developed to fabricate the 3D MEA master structure. The MEAs themselves are fabricated from the master structure utilizing micromolding techniques. Metal patterns are transferred during the micromolding process, thereby ensuring reduced process steps compared to traditional silicon-based approaches. These 3D MEAs have been packaged utilizing biocompatible Kapton® substrates. ESEI measurements have been carried out on test human subjects with standard commercial wet electrodes as a reference. The 3D MEAs demonstrate an order of magnitude lower ESEI (normalized to area) compared to wet electrodes for an area that is 12.56 times smaller. This compares well with other demonstrated approaches in literature. For a nerve tracking demonstration, we have chosen EMG and nerve conduction measurements on test human subjects. The 3D MEAs show 100% improvement in signal power and SNR/√area as compared to standard electrodes. They also demonstrate larger amplitude signals and faster rise times during nerve conduction measurements. We believe that this microfabrication and packaging approach scales well to large-area, high-density arrays required for applications like nerve tracking. This development will increase the stimulation and recording fidelity of skin surface electrodes, while increasing their spatial resolution by an order of magnitude or more. Although biopotential electrode systems are not without their challenges, the non-invasive access to neural information, along with the potential for automation with associated electronic and software development, is precisely what makes this technology an excellent candidate for the next generation in diagnostic, therapeutic, and prosthetic devices.

Three-dimensional micro-electrode array for recording dissociated neuronal cultures

This work demonstrates the design, fabrication, packaging, characterization, and functionality of an electrically and fluidically active three-dimensional micro-electrode array (3D MEA) for use with neuronal cell cultures. The successful function of the device implies that this basic concept-construction of a 3D array with a layered approach-can be utilized as the basis for a new family of neural electrode arrays. The 3D MEA prototype consists of a stack of individually patterned thin films that form a cell chamber conducive to maintaining and recording the electrical activity of a long-term three-dimensional network of rat cortical neurons. Silicon electrode layers contain a polymer grid for neural branching, growth, and network formation. Along the walls of these electrode layers lie exposed gold electrodes which permit recording and stimulation of the neuronal electrical activity. Silicone elastomer micro-fluidic layers provide a means for loading dissociated neurons into the structure and serve as the artificial vasculature for nutrient supply and aeration. The fluidic layers also serve as insulation for the micro-electrodes. Cells have been shown to survive in the 3D MEA for up to 28 days, with spontaneous and evoked electrical recordings performed in that time. The micro-fluidic capability was demonstrated by flowing in the drug tetrotodoxin to influence the activity of the culture.

Design and fabrication of novel three-dimensional multi-electrode array using SOI wafer

A novel method has been developed for the manufacture of a three-dimensional multi-electrode array (3D MEA), particularly, the shape of micro-tips can be varied by MEMS technology to construct different multi-electrode array. It improved the disadvantage of single electrode, which meant that it was available for multi-recording and analysis of a series of signals. Overcoming the difficulty of making interconnection line on 3D MEA chips via innovative fabrication process design. Using local isolation and removal of oxide films to forming electrodes and interconnections with oxide isolation covers. A 10 × 10 3D MEA with a distance of 100 μm between each other for further bio-neural signals was demonstrated, and a test on rabbit retina was also available. Besides, integrating pre-amplifier and built-in resistors with 3D MEA was brought out to hopefully increase the efficiency of sensing.