A Multipurpose CMOS Platform for Nanosensing

Abstract

This paper presents a customizable sensing system based on functionalized nanowires (NWs) assembled onto complementary metal oxide semiconductor (CMOS) technology. The Micro-for-Nano (M4N) chip integrates on top of the electronics an array of aluminum microelectrodes covered with gold by means of a customized electroless plating process. The NW assembly process is driven by an array of on-chip dielectrophoresis (DEP) generators, enabling a custom layout of different nanosensors on the same microelectrode array. The electrical properties of each assembled NW are singularly sensed through an in situ CMOS read-out circuit (ROC) that guarantees a low noise and reliable measurement. The M4N chip is directly connected to an external microcontroller for configuration and data processing. The processed data are then redirected to a workstation for real-time data visualization and storage during sensing experiments. As proof of concept, ZnO nanowires have been integrated onto the M4N chip to validate the approach that enables different kind of sensing experiments. The device has been then irradiated by an external UV source with adjustable power to measure the ZnO sensitivity to UV-light exposure. A maximum variation of about 80% of the ZnO-NW resistance has been detected by the M4N system when the assembled 5 μm × 500 nm single ZnO-NW is exposed to an estimated incident radiant UV-light flux in the range of 1 nW–229 nW. The performed experiments prove the efficiency of the platform conceived for exploiting any kind of material that can change its capacitance and/or resistance due to an external stimulus.

A CMOS Multi-Electrode Array for Four-Electrode Bioimpedance Measurements

“…Several authors have used the ENIG process for plating MEAs with individual differences such as electrode geometry and processing steps. We have based our deposition on the processes described by Niitsu et al [25] and Bonanno et al [27], but with different electrode shapes and another gold plating solution. Since handling mm sized chips can be difficult, a strainer was 3D printed in formlabs standard resin for moving the chips between the different chemicals used in the plating process.…”

Low-power architecture for integrated CMOS bio-sensing

“…Regarding the second point, about the use for in in vivo applications, standard CMOS materials are not the best choice both because of native oxide formation (e.g., Al, Cu) and intrinsic medium/long term toxicity (e.g., Cu). For these reasons some additional post processing (such as electro-or electroless deposition) could be required to make the CMOS more biocompatible [14], [15]. The third point, i.e., new architectures, is what we want to propose and motivate here.…”

A Scalable and Low Stress Post-CMOS Processing Technique for Implantable Microsensors

“…), including systems-on-chip. Examples range from MEMS (microelectromechanical) integrated systems [ 1 , 2 ] to microfluidic devices [ 3 , 4 , 5 , 6 ], and bio/chemical sensors [ 7 , 8 , 9 , 10 , 11 ]. Among those applications, the development of wireless microscale neural implants using CMOS has been explored as one approach for next-generation brain–machine interfaces (BMI) by several groups [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…These might include building biocompatible microelectrodes on contact pads, applying coatings for hermetic sealing, and so on, which typically requires microfabrication processes such as lithography, metallization, etching, and bonding on the CMOS die. In a CMOS process, aluminum that is often used as a top metal is oxidized over time, which can disrupt the electrical interface with biological tissue, as one example [ 8 , 9 ]. For this problem, stable and biocompatible alternative materials such as gold (Au), platinum–iridium alloy, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are attractive to provide long-term reliability of the electrode–tissue interface and electrode–electrolyte impedance optimization [ 19 , 20 , 21 , 22 , 23 , 24 ].…”