3D Electrode Array Research Articles

Structural Electronic Skin for Conformal Tactile Sensing.

The conformal integration of the electronic skin on the non-developable surface is in great demand for the comprehensive tactile sensing of robotics and prosthetics. However, the current techniques still encounter obstacles in achieving conformal integration of film-like electronic skin on non-developable surfaces with substantial curvatures for contact pressure detection and tactile mapping. In this paper, by utilizing the 3D printing technology to prepare the 3D electrode array in the structural component following its surface curvature, and covering it with a molded functional shell to form the pressure sensitive iontronic interface, a device is proposed to achieve high-sensitive pressure detection and high-fidelity tactile mapping on a complicated non-developable surface, called structural electronic skin (SES). The SES is prepared in a 3D printed fingertip with 46 tactile sensing units distributed on its curved surface, achieving the integration of both structural and tactile functions in a single component. By integrating the smart fingertip into a dexterous hand, a series of demonstrations are presented to show the dead-zone free pressure detection and tactile mapping with high sensitivity, for instance, 2D pulse wave monitoring and robotic injection in a medical robot, object recognition and compliant control in a smart prosthesis.

High-Performance Solid-State Lithium-Ion Battery with Mixed 2D and 3D Electrodes

It is well established that the miniaturization of batteries has not kept pace with the miniaturization of electronics. Three-dimensional (3D) batteries, which were developed with the intent of improving microbattery performance, have had limited success because of fabrication challenges and material constraints. Solid-state, 3D batteries have been particularly susceptible to these shortcomings. In this paper we demonstrate that the incorporation of a high conductivity, solid electrolyte is the key to achieving a non-planar solid-state battery with high areal-capacity and high power-density. The model, 2.5D platform used in this study is a modification of the more typical 3D configuration in that it is comprised of a cathode array of pillars (3D) and a planar (2D) anode. This 2.5D geometry exploits the use of a high conductivity, ionogel electrolyte (10-3 S cm-1) which interpenetrates the 3D electrode array. The 2.5D battery offers high areal energy densities from the post array while the high-conductivity, solid electrolyte enables high power densities (3.7 mWh cm-2 at 2.8 mW cm-2). The reported solid-state 2.5D device exceeds the energy and power densities of any 3D solid-state system and the derived multiphysics model provides guidance for achieving significantly higher energy and power densities.

Electrodeposition and Characterization of Manganese Dioxide Thin Films on Silicon Pillar Arrays for 3D Thin-Film Lithium-Ion Batteries

Due to the increasing power requirements of the electronic devices and emerging technologies (e.g., wireless transmission), Li-ion batteries should be improved to provide higher energy and power densities on a small area (e.g. <1 cm2). To date, one promising way to maximize the energy and power densities of battery is to be built using 3D structured electrodes. Such electrodes are designed to make shorter ions diffusion paths and improving electrons harvesting pathways [1,2].In this context, the present work focuses onthe electrochemical deposition of manganese dioxide thin films on high aspect ratio silicon pillar arrays coated with carbon as a technologically-relevant current collector and the investigation of their properties as positive electrode material for Li-ions batteries. As 3D electrode array, hexagonally arranged Si pillars of 2um in diameter and 2um spacing were etched 60um deep in the silicon by reactive ion etching (RIE) using a SiO2 hard mask. The pillars were coated with about 20nm TiN by atomic layer deposition (ALD), acting as diffusion barrier for lithium into silicon. Cases of conformal coatings of electrolytic manganese dioxide (EMD) directly on the conductive TiN barrier were compared with seeded TiN / silicon pillars. In this respect, thin carbon coatings were evaluated as technological relevant alternative for platinum. For this, about 30nm of carbon was grown on ALD TiN / silicon pillars by chemical vapor deposition (CVD) from CH4/H2 mixture. The platinum seed films were made by ALD process. The electrolytic manganese dioxide (EMD) films were anodically deposited from an aqueous solution of 0.3 M MnSO4·xH2O + 0.55 M H2SO4. Since the oxidation of TiN takes place in the same potential region as does EMD deposition a protective layer such as platinum can be used to prevent TiN from oxidation during the aqueous deposition of MnO2 [3]. Here we evaluated carbon as technologically relevant alternative. Figure 1 shows cyclic voltamogrammes for uncoated and carbon coated planar TiN substrates. The EMD film thickness on TiN is strongly limited due to oxidation of the TiN. The carbon successfully protects the TiN from oxidation such that much thicker films can be made similarly to what was found with Pt seed layers before [4].The physical characteristics of the EMD films has been primarily investigated on planar substrates. The crystal structure of the EMD films before and after lithiation were characterized by X-ray diffraction (XRD). The porosity of the EMD films was determined by comparison of Rutherford backscattering (RBS) and Scanning electron microscopy (SEM). The porosity of the films typically ranges between 40-60%, depending on film thickness and substrate.After removing the water content in the films by thermal annealing, the electrochemical activity of EMD films was studied in propylene carbonate solvent with 1M LiClO4.Reversible insertion and extraction of Li+ was observed. Electrochemical lithiation and delithiation experiments showed an improved cycle performance for carbon coated TiN substrates compared to Pt coated TiN substrates. The difference is attributed to decreased porosity (attachment) for the EMD to the C surface compared to platinum surface. The average lithium storage capacity for planar EMD films is about 50mAh/cm2 per mm (at 10mV/s comparable with charging rate of 20C). Based on a surface area gain of 28for the 3D pillar structures, a capacity of 0.2mAh/cm2is expected for conformal coated 200 nm film at these high rates.REFERENCES[1] M. Roberts, P. Johns, J. Owen, D. Brandell, K. Edström, G. Enany, C. Guery, D. Golodnitsky, M. Lacey, C. Lecoeur, H. Mazor, E. Peled, E. Perre, M. M. Shaijumon, P. Simon, P. L. Taberna, J. Mater. Chem. 21, 9876 (2011)[2] A. H. Whitehead and M. Schreiber, Journal of The Electrochemical Society, 152, A2105 (2005) [3] D. J. Cott, M. Verheijen, O. Richard, I. Radu, S. De Gendt, S. van Elshocht, and P. M. Vereecken, Carbon, 58 59 (2013).[4] "Effect of Film Morphology on the Li-ion Intercalation Kinetics in Anodic Porous Manganese Dioxide Thin-Films" A. Etman, A. Radisic, E. Mahmoud, C. Huyghebaert, P.M. Vereecken, submitted to Journal of Physical Chemistry.

Mathematical modeling and reliability analysis of a 3D Li-ion battery

The three-dimensional (3D) Li-ion battery presents an effective solution to issues affecting its two-dimensional counterparts, as it is able to attain high energy capacities for the same areal footprint without sacrificing power density. A 3D battery has key structural features extending in and fully utilizing 3D space, allowing it to achieve greater reliability and longevity. This study applies an electrochemical-thermal coupled model to a checkerboard array of alternating positive and negative electrodes in a 3D architecture with either square or circular electrodes. The mathematical model comprises the transient conservation of charge, species, and energy together with electroneutrality, constitutive relations and relevant initial and boundary conditions. A reliability analysis carried out to simulate malfunctioning of either a positive or negative electrode reveals that although there are deviations in electrochemical and thermal behavior for electrodes adjacent to the malfunctioning electrode as compared to that in a fully-functioning array, there is little effect on electrodes further away, demonstrating the redundancy that a 3D electrode array provides. The results demonstrate that implementation of 3D batteries allow it to reliably and safely deliver power even if a component malfunctions, a strong advantage over conventional 2D batteries.

Design, Fabrication and Characterization of a Low-Impedance 3D Electrode Array System for Neuro-Electrophysiology

Recent progress in patterned microelectrode manufacturing technology and microfluidics has opened the way to a large variety of cellular and molecular biosensor-based applications. In this extremely diverse and rapidly expanding landscape, silicon-based technologies occupy a special position, given their statute of mature, consolidated, and highly accessible areas of development. Within the present work we report microfabrication procedures and workflows for 3D patterned gold-plated microelectrode arrays (MEA) of different shapes (pyramidal, conical and high aspect ratio), and we provide a detailed characterization of their physical features during all the fabrication steps to have in the end a reliable technology. Moreover, the electrical performances of MEA silicon chips mounted on standardized connector boards via ultrasound wire-bonding have been tested using non-destructive electrochemical methods: linear sweep and cyclic voltammetry, impedance spectroscopy. Further, an experimental recording chamber package suitable for in vitro electrophysiology experiments has been realized using custom-design electronics for electrical stimulus delivery and local field potential recording, included in a complete electrophysiology setup, and the experimental structures have been tested on newborn rat hippocampal slices, yielding similar performance compared to commercially available MEA equipments.

A continuous high-throughput bioparticle sorter based on 3D traveling-wave dielectrophoresis

We present a high throughput (maximum flow rate approximately 10 microl/min or linear velocity approximately 3 mm/s) continuous bio-particle sorter based on 3D traveling-wave dielectrophoresis (twDEP) at an optimum AC frequency of 500 kHz. The high throughput sorting is achieved with a sustained twDEP particle force normal to the continuous through-flow, which is applied over the entire chip by a single 3D electrode array. The design allows continuous fractionation of micron-sized particles into different downstream sub-channels based on differences in their twDEP mobility on both sides of the cross-over. Conventional DEP is integrated upstream to focus the particles into a single levitated queue to allow twDEP sorting by mobility difference and to minimize sedimentation and field-induced lysis. The 3D electrode array design minimizes the offsetting effect of nDEP (negative DEP with particle force towards regions with weak fields) on twDEP such that both forces increase monotonically with voltage to further increase the throughput. Effective focusing and separation of red blood cells from debris-filled heterogeneous samples are demonstrated, as well as size-based separation of poly-dispersed liposome suspensions into two distinct bands at 2.3 to 4.6 microm and 1.5 to 2.7 microm, at the highest throughput recorded in hand-held chips of 6 microl/min.