Muthu B. J. Wijesundara

SiC Materials and Processing Technology

This chapter contains a broad review of SiC materials and processing technology necessary to create SiC electronics, micromechanical transducers, and packaging. Details on deposition and etching methods are covered. The material properties of various forms of SiC (single crystalline, polycrystalline, and amorphous) along with their use for creating the various components of harsh environment microsystems will also be discussed. Current status and future research are highlighted with regards to both materials and processing technologies.

EHD printing of PEDOT: PSS inks for fabricating pressure and strain sensor arrays on flexible substrates

Robotic skins with multi-modal sensors are necessary to facilitate better human-robotic interaction in non-structured environments. Integration of various sensors, especially onto substrates with non-uniform topographies, is challenging using standard semiconductor fabrication techniques. Printing is seen as a technology with great promise that can be used for sensor fabrication and integration as it may allow direct printing of different sensors onto the same substrate regardless of topology. In this work, we investigate Electro-Hydro-Dynamic (EHD) printing, a method that allows printing of micron-sized features with a wide range of materials, for fabricating pressure sensor arrays using Poly(3,4- ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS). Fabrication of such sensors has been achieved by prepatterning gold or platinum metallized interdigitated comb electrode arrays on a polyimide substrate, with three custom made PEDOT:PSS based inks printed directly onto the electrode arrays. These three inks include a formulation of PEDOT:PSS and NMP; PEDOT:PSS, PVP, and NMP; and PEDOT:PSS, PVP, Nafion, and NMP. All these inks were successfully printed onto sensor elements. The initial results of bending-induced strain tests on the fabricated sensors display that all the inks are sensitive to strain. This confirms their suitability for pressure and strain sensor applications; however, the behavior of each ink; including sensitivity, linearity, and stability; is unique to the type.

Sensorized soft robotic glove for continuous passive motion therapy

This paper presents the design and development of a sensorized soft robotic glove based on pneumatic soft-and-rigid hybrid actuators for providing continuous passive motion (CPM) in hand rehabilitation. This hybrid actuator is comprised of bellow-type soft actuator sections connected through block-shaped semi-rigid sections to form robotic digits. The actuators were designed to satisfy the anatomical range of motion for each joint. Each digit was sensorized at the tip with an inertial measurement unit sensor in order to track the rotation of the distal end. A pneumatic feedback control system was developed to control the motion of the soft robotic digit in following desired trajectories. The performance of the soft robotic glove and the associated control system were examined on an able-bodied subject during flexion and extension to show the gloves applicability to CPM applications.

Design and Development of a Novel Soft-and-Rigid Hybrid Actuator System for Robotic Applications

This paper presents the design and development of a pneumatic soft-and-rigid hybrid actuator system that consists of half-bellow shaped soft sections in-between block shape rigid sections. The hybrid actuator architecture allows for selective actuation of each soft section (acting as a joint) with precise control over its bending motion. The soft half-bellow section is designed as a series of hollow ridges extending straight to a flat base. This geometry provides forward and backward bending motion when subjected to positive and negative pressure, respectively. Bending occurs as the ridges of the soft section expand and contract more than the flat base due to pressure variations. The rigid sections serve as connections between soft actuator sections and enhance force transfer. As a case study, a hybrid actuator system was designed as a soft robotic digit with three soft joints and four rigid connecting sections. Finite element analysis was performed to evaluate the design parameters such as number of ridges and materials for the robotic finger. The joints (from proximal to distal) were designed to have four, three, and two ridges, respectively, to generate the desired range of angular motion. Fabrication of the finger was done with silicone rubber RTV-4234-T4 and PMC polyurethane rubber using a combination of compression molding and overmolding processes. The angular and translational displacements of the robotic finger were experimentally and numerically evaluated at different pressures. The trajectory of the fingertip is comparable to those reported in literature for continuous soft actuators with a similar length. The significance of this actuator system is that both range of angular and translational motions are achieved at low pressure, less than 70kPa, as opposed to reported pressures of greater than 100kPa. The presented results show the great potential of the soft robotic finger for use in robotic, rehabilitation, and assistive device applications.Copyright

A novel Microchannel Electrode Array: Towards bioelectronic medical interfacing of small peripheral nerves

Bioelectronic medicine is an emerging field that relies on electrical signals to modulate complex neuronal circuits, particularly in the peripheral nervous system, as an alternative to drug-enabled therapeutics. Small autonomic nerves are one of the targets in this field, however, interfacing peripheral nerves smaller than 300 μm remains a challenge. Here we report the development of a Microchannel Electrode Array (DCEA) capable of interfacing nerve fascicles as small as 50-300μm. The current μCEA records and stimulates from 28 channels and is designed for easy implantation and removal, bearing promise to enable neural interfacing in BM.

EHD as sensor fabrication technology for robotic skins

Human-robot interaction can be made more sophisticated and intuitive if the entire body of a robot is covered with multimodal sensors embedded in artificial skin. In order to efficiently interact with humans in unstructured environments, robotic skin may require sensors such as touch, impact, and proximity. Integration of various types of sensors into robotic skin is challenging due to the topographical nature of skin. Printing is a promising technology that can be explored for sensor integration as it may allow both sensors and interconnects to be directly printed into the skin. We are developing Electrohydrodynamic (EHD) inkjet printing technology in order to co-fabricate various devices onto a single substrate. Using strong applied electrostatic forces, EHD allows the printing of microscale features from a wide array of materials with viscosities ranging from 100 to 1000cP, highly beneficial for multilateral integration. Thus far we have demonstrated EHD’s capability at printing patterns of Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) for pressure sensor applications, generating patterns with modified commercial photoresist for mask-less lithography, and obtaining ZnO microstructures for direct device printing. Printed geometries range from a few tens of microns to millimeters. We have used inks with viscosities ranging from 230 to 520cp and from non-conductive to 135μS/cm. These results clearly show that the EHD is a promising multi-material printing platform and would be an enabling technology that can be used to co-fabricate various devices into robotic skin.

Silicon Carbide Electronics

One of the major benefits of silicon carbide for harsh environment microsystems is the ability to create high temperature electronics from a corrosion resistance base material. Because silicon carbide is a wide band semiconductor, it is more robust to high temperature excursions. But silicon carbide electronics requires the ability to create a substrate and thin-film layers that are high purity and can be doped in a controlled manner. Thematerials developments outlined in Chapter 2 lay the foundation for developing silicon carbide electronics. Besides being able to create doped, highpurity films, silicon carbide electronics requires a way to create localized doped regions in order to create specific transistor topologies as well as a metallization scheme for routing signals. This chapter will begin with a generalized process flow for creating silicon carbide electronics, followed by discussions on ion implantation doping and electrical contacts for silicon carbide. Then different electrical device topologies explored in silicon carbide will be described in the context of high power switching, high temperature amplifiers, and wireless communication.

Pneumatic actuator inserts for interface pressure mapping and fit improvement in lower extremity prosthetics

The fit of a prosthetic socket to a residual limb is critical as poor socket fit is one of the leading causes of improper function, discomfort, and skin breakdown. The daily and long term volume fluctuation of a residual limb presents a major challenge to maintaining fit. This work presents the initial efforts to develop adjustable inserts that consisted of arrays of small, sensorized inflatable pressure actuators that can expand based on the volume change. We have fabricated and tested actuator inserts to demonstrate their capability for pressure mapping in a limb-socket interface. We have also shown that the actuators have the capacity to maintain positive displacement under load to accommodate for volume change in a residual limb for improved fit.

Front Matter: Volume 9859

This PDF file contains the front matter associated with SPIE Proceedings Volume 9859, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

A flexible microchannel electrode array for peripheral nerves to interface with neural prosthetics

In order to control neural prosthetics by recording signals from peripheral nerves with the required specificity, high density electrode arrays that can be easily implanted on very small peripheral nerves (50μm-500μm) are needed. Interfacing with these small nerves is surgically challenging due to their size and fragile nature. To address this problem, a Flexible MicroChannel Electrode Array for interfacing with small diameter peripheral nerves and nerve fascicles was developed. The electrochemical characterization and electrophysiological recordings from the common peroneal nerve of a rat are presented along with demonstration of the surgical ease-of-use of the array.