Integration technologies for implantable microsystems

Microsystems targeted for implantation require careful consideration of power, thermals, size, reliability, and biocompatibility. The presented research explored appropriate integration technologies for an implantable drug delivery system suitable for use in mice weighing less than 20 grams. Microsystems technology advancements include in situ pump diaphragm formation; integrated, low volume microfluidic coupling technologies; and incorporation of a low voltage, low-power pump actuation with a zero-power off state. Utility of the developed integration technologies have been tested through in vitro reliability and validation experiments. A four-chamber peristaltic pump was created using micromachining (e.g. thin film deposition and Si etching) and direct write techniques. A novel phase change material based actuator was designed and fabricated to deflect deformable diaphragms into and out of four pump chambers while the diaphragms isolated the pumped fluid from the working material. Polyimide capillary tubing with 140-μm OD was integrated in-plane and acted as fluidic interconnects to a drug supply and to the pharmaceutical delivery site. Parylene C conformal coating and the design for gap occlusion provided sealed, flexible tubing connections to the micropump. The per chamber actuation power of 10.1 mW at 0.083 Hz resulted in fluid flow of over 100 nL/min with an efficiency of 11 mJ/nL

Investigating the Design and Manufacture of PneuNet Actuators as a Prosthetic Tongue for Mimicking Human Deglutition

The number of Total Glossectomy cases in the United States is seeing an increasing trend as per the Nationwide Inpatient Sample Database. Patients, who have undergone such aggressive surgical procedures, have extensive limitations performing basic oral functions such as swallowing (deglutition), eating and speaking. Current rehabilitation prostheses do little in restoring the functionality of the original tongue. This is true especially in deglutition, which is necessary to transfer a bolus to the esophagus. Such patients need advanced prosthetic devices and through this research, investigations into potential solutions for prosthetic tongues to aid in deglutition were carried out. The process began with an extensive literature review that provided tongue position, motion, and pressure data during the swallowing stages. Several potential designs were considered such as using linkages and pneumatic networks (PneuNets). Based on a decision matrix, PneuNets were adopted as the foundational basis for generating prosthetic designs. Several prototypes were fabricated using Fused Filament Disposition for mold development and silicone Eco-flex 00-30 for actuator development. Each iteration involved tackling several design and manufacturing challenges especially when scaling these actuators from an initial experiment to an anatomical shape and size of a human tongue. A tongue of dimensions 1.8 inches wide, 2.4 inches long and 0.24 inches thick was developed. The PneuNet actuator was powered by a pneumatic system and kinematic data was collected using a tracking software. The data gathered provided validation comparisons between position trends exhibited in the literature. Theoretical deflection models were generated for analyzing the deflection of the front, middle and back sections of the tongue prototype. Details from literature review, design iterations, simulations, validation processes, research challenges and conclusions will be discussed in depth

The development of artificial muscles using textile structures

The aim of this project was to investigate the use of textile structures as muscles to assist people with muscular deficiency or paralysis. Due to the average life expectancy continuing to increase, support for those needing assistance to move unaided is also increasing. The purpose of this project was to try to help a patient who would normally need assistance, to move their arm unaided. It could also help with rehabilitation of muscular injuries and increasing strength and reducing muscular fatigue of manual workers. The approach considered was to develop an extra corporal device for the upper limbs, providing the main required motions. Most devices currently available use motors and gearboxes to assist in limb movement. This study investigated a way of mimicking the contraction of biological skeletal muscles to create a motion that is as human as possible with a soft, flexible and lightweight construction. Electroactive polymers (EAPs) and pneumatic artificial muscles (PAMs) were investigated. It became clear that at present, the EAPs were unable to create the forces and speed of contraction required for this application. The use of pneumatics to create artificial muscles was developed upon. PAMs, like the McKibben muscle and the pleated pneumatic muscle mimic the natural contraction of skeletal muscle. These current PAMs were used as a basis to develop a new type of pneumatic artificial muscle in this project. A 90 mm ball-like structure was developed, produced from an air impermeable rubber coated cotton fabric. Joining three oval panels together created a 3-D spherical shape. Three of these structures were linked together, and when inflated, created an acceptable level of contraction and force. This method of producing artificial muscles created a soft, lightweight and flexible actuator with scope for different arrangements, sizes and positions of the muscle structure. The contraction process was mathematically modelled. This calculated the predicted rate and level of contraction of a 2-D muscle structure. These mathematical findings were able to be compared to the practical results, and produced similar contraction characteristics. The muscle structures were incorporated into a garment to form a type of muscle suit which could be worn to assist movement. This garment has an aluminium frame to protect the wearer's bones from stresses from the contracting muscles. This study has shown that the muscle suit developed can create movement for wearers that would normally need assistance, and also reduce muscle fatigue, which would be useful for manual workers. This is incorporated into a functional and wearable garment, which is easy to dress and more lightweight and aesthetically pleasing than current muscle suits.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Development of a Physical Simulation of the Human Defecatory System for the Investigation of Continence Mechanisms

Faecal incontinence is a highly debilitating condition, prevalent across the population worldwide. Coupled with a large unmet need for clinically viable treatment options, a paucity of research into the biomechanics of continence inhibits the development of treatments which address multi-faceted challenges associated with the condition. Consequently, this thesis presents a method to fabricate, measure and control a physical simulation of the human defecatory system to investigate individual and combined effects of anorectal angle and sphincter pressure on continence. To illustrate the capabilities and clinical relevance of the work, the influence of a passive-assistive artificial anal sphincter (FENIX) is evaluated. A model rectum and associated soft tissues, based on geometry from an anonymised computerised tomography dataset, was fabricated from silicone and showed behavioural realism in terms of their morphology to the biological system and ex-vivo tissue. Simulated stool matter with similar rheological properties to human faeces was developed. Instrumentation and control hardware were used to regulate injection of simulated stool into the system, define the anorectal angle and monitor stool flow rate, intra-rectal pressure, anal canal pressure and puborectalis force. Studies were conducted to examine the response of anorectal angles at 80°, 90° and 100° with simulated stool. Tests were then repeated with the inclusion of a FENIX device. Stool leakage was reduced as the anorectal angle became more acute. Conversely, intra-rectal pressure increased. Overall inclusion of the FENIX reduced faecal leakage, while combined effects of the FENIX and an acute anorectal angle showed the greatest resistance to faecal leakage. These data demonstrate that the anorectal angle and sphincter pressure are fundamental in maintaining continence. Furthermore it demonstrates that use of the FENIX can increase resistance to faecal leakage and reduce anorectal angles required to maintain continence. The physical simulation of the defecatory system is an insightful tool to better understand, in a quantitative manner, the effects of the anorectal angle and sphincter pressure on continence. This work is valuable in helping improve our understanding of the physical behaviour of the continence mechanism and facilitating improved technologies to treat severe faecal incontinence

Functional Materials and Techniques for Additive Manufacturing in Soft Robotics

This thesis outlines the development of new elastomeric materials and manufacturing processes for soft robotics. Specifically, this work describes the development of custom material formulations for use in additive manufacturing, additive manufacturing processing techniques for silicone elastomers, and multi-component additive manufacturing techniques. Material synthesis and processing is a gap in the field that needs more research to produce more predictable, higher quality, and more scalable soft robot technologies. This thesis includes papers that address the above topics, preceded by an introduction and literature review into additive manufacturing and materials characterization for soft robotics. The first work (Chapter 2) outlines the development of a custom elastomer designed to make biodegradable soft robots via 3D printing. The second work (Chapter 3) shows how liquid silicone thermoset polymers 3d printing can be improved by controlling reaction kinetics and rheology. The last work (Chapter 4) describes the process of using silicone 3D printing to embed multiple discrete sensing and electronic components into a functioning soft wearable device, with a focus on customizability. Each work describes a different part of how materials science plays a role in soft robotics, including the creation of elastomeric material, control of the elastomeric material, and combining the multiple materials in custom device manufacturing. For each work, a soft robot actuator or robot system is developed to emphasize the importance of material behavior and process development in improving soft robot manufacturing

Neurodegeneration and Neuroplasticity of the Intrinsic Innervation of the Gut in Severe Dysmotility

Abnormalities in the gastrointestinal neuromuscular apparatus including interstitial cells of Cajal (ICC) is presumed to underlie a clinically heterogeneous group of disorders collectively termed gastrointestinal neuromuscular diseases (GINMDs). A subset of these patients may manifest clinically with recurrent intestinal sub-occlusive episodes, which occur in the absence of demonstrable mechanical causes, leading to numerous hospitalizations as well as useless and potentially harmful surgical interventions. Taken together clinical and radiological signs make up a condition referred to as chronic intestinal pseudo-obstruction (CIPO). This is a rare and intractable chronic digestive disease that can result from abnormalities of smooth muscle cells (effectors of contractility / relaxation), ICC (pace-makers of gut motility and regulators of neuronal input to smooth muscle cells), and neurons (either intrinsic – the enteric nervous system- or extrinsic nerve pathways). The present thesis was thought to provide a translational view by characterizing dysmotility and establishing attendant histopathological defects in CIPO and determine whether a correlation exists between clinical features, motility patterns and neuromuscular changes, using qualitative and quantitative morphological approaches. In this thesis I provided an update on neurointestinal diseases, with special focus on diagnostic, therapeutic and management aspects of CIPO, which have been published during the PhD course. My senior dissertation deals with major neurogastroenterological aspects, such as those involving the most severe forms of the functional GI disorder spectrum, i.e. those patients with prominent abnormalities of gut propulsion. A better understanding of these cases will cast hope about patient management and newly applicable therapeutic intervention