Development of a Fabrication Technique for Soft Planar Inflatable Composites

Soft robotics is a rapidly growing field in robotics that combines aspects of biologically inspired characteristics to unorthodox methods capable of conforming and/or adapting to unknown tasks or environments that would otherwise be improbable or complex with conventional robotic technologies. The field of soft robotics has grown rapidly over the past decade with increasing popularity and relevance to real-world applications. However, the means of fabricating these soft, compliant and intricate robots still poses a fundamental challenge, due to the liberal use of soft materials that are difficult to manipulate in their original state such as elastomers and fabric. These material properties rely on informal design approaches and bespoke fabrication methods to build soft systems. As such, there are a limited variety of fabrication techniques used to develop soft robots which hinders the scalability of robots and the time to manufacture, thus limiting their development. This research focuses towards developing a novel fabrication method for constructing soft planar inflatable composites. The fundamental method is based on a sub-set of additive manufacturing known as composite layering. The approach is designed from a planar manner and takes layers of elastomeric materials, embedded strain-limiting and mask layers. These components are then built up through a layer-by-layer fabrication method with the use of a bespoke film applicator set-up. This enables the fabrication of millimetre-scale soft inflatable composites with complex integrated masks and/or strain-limiting layers. These inflatable composites can then be cut into a desired shape via laser cutting or ablation. A design approach was also developed to expand the functionality of these inflatable composites through modelling and simulation via finite element analysis. Proof of concept prototypes were designed and fabricated to enable pneumatic driven actuation in the form of bending soft actuators, adjustable stiffness sensor, and planar shape change. This technique highlights the feasibility of the fabrication method and the value of its use in creating multi-material composite soft actuators which are thin, compact, flexible, and stretchable and can be applicable towards real-world application

Scalability study for robotic hand platform

The goal of this thesis project was to determine the lower limit of scale for the RIT robotic grasping hand. This was accomplished using a combination of computer simulation and experimental studies. A force analysis was conducted to determine the size of air muscles required to achieve appropriate contact forces at a smaller scale. Input variables, such as the actuation force and tendon return force, were determined experimentally. A dynamic computer model of the hand system was then created using Recurdyn. This was used to predict the contact (grasping) force of the fingers at full-scale, half-scale, and quarter-scale. Correlation between the computer model and physical testing was achieved for both a life-size and half-scale finger assembly. To further demonstrate the scalability of the hand design, both half and quarter-scale robotic hand rapid prototype assemblies were built using 3D printing techniques. This thesis work identified the point where further miniaturization would require a change in the manufacturing process to micro-fabrication. Several techniques were compared as potential methods for making a production intent quarter-scale robotic hand. Investment casting, Swiss machining, and Selective Laser Sintering were the manufacturing techniques considered. A quarter-scale robotic hand tested the limits of each technology. Below this scale, micro-machining would be required. The break point for the current actuation method, air muscles, was also explored. Below the quarter-scale, an alternative actuation method would also be required. Electroactive Polymers were discussed as an option for the micro-scale. In summary, a dynamic model of the RIT robotic grasping hand was created and validated as scalable at full and half-scales. The model was then used to predict finger contact forces at the quarter-scale. The quarter-scale was identified as the break point in terms of the current RIT robotic grasping hand based on both manufacturing and actuation. A novel, prototype quarter-scale robotic hand assembly was successfully built by an additive manufacturing process, a high resolution 3D printer. However, further miniaturization would require alternate manufacturing techniques and actuation mechanisms

Unconventional elastomeric microsystems: fabrication and application

Elastomer-based microsystems hold great promise for a diverse range of applications such as rapid prototyping of lab-on-a-chip device, soft-MEMS, and soft-robotics. For better performance in such applications, unconventional elastomeric structures in terms of size, shape, and patterning trajectory, have been intensely sought after in microtechnology but their realization has been a continuous challenge. Here, as my dissertation work, I present new microfabrication schemes which enable the realizations of unconventional PDMS structures, and their applications, which will enrich the field of soft-microsystems. First, I present a new fabrication scheme for the realization of cylindrical microfluidic (MF) channels with 3D trajectories based on shaping, bonding, and assembly of sucrose fibers. Due to the high water-solubility of the sucrose templates, the scheme is a simple and environment-friendly. Also, it is cleanroom-free and cost-effective. Despite its simplicity, it enables the realization of essential 3D MF channel architectures such as highly curved MF channels, internal loops, and proper end-to-side junctions. It can, also, realize tapered junctions and stenosis which can benefit vaso-mimetic lab-on-a-chip applications. Secondly, as a practical application of the sucrose-based MF channel, I report the implementation of the bokeh-effect-based microfluidic microscopy scheme for point-of care health monitoring in highly resource-limited environment. For this work, I integrated a single polymer microlens over the sucrose-templated MF channel and retrieved magnified intra-channel images with a commercial, off-the-shelf camera. The bokeh microscope exhibited 10∼40 in magnification and 67∼252 μm of field-of-view extent, confirming their utility for point-of-care monitoring of micro-scale objects in MF channels Third, I present a new technique that enables facile fabrications of high aspect-ratio PDMS micropillars exceeding 2400 m in height and 100 in aspect-ratio. The key enabling factor is the adoption of the direct drawing technique incorporated with the in situ heating for simultaneous hardening and solidification of PDMS. The technique also allows self-aligned installation of highly reflective microspheres at the tips of the micropillars. Using the transparent PDMS micropillar as a flexible waveguide and the microsphere as a self-aligned reflector, I transformed the microsphere-tipped PDMS micropillars into all optically interrogated air-flow sensors and successfully demonstrated its air-flow sensing capability. Lastly, I present a microscale soft-robotic tentacle with spiral bending capability based on pneumatically driven bending motion of a hollow PDMS microtube. For this work, I establish a new, direct peeling-based technique for building long and thin, highly deformable microtubes and a semi-analytical model for their shape-engineering. Based on them, the artificial microrobotic tentacle exhibits the multi-turn spiraling motion with the final radius of 185 μm and squeezing force of ~ 0.78 mN. Thanks to the softness of PDMS and the spiraling motion, the micro-tentacle can function as a soft-robotic grabber of fragile micro-objects. The spiraling tentacle-based grabbing modality, the elastomeric microtube fabrication technique, and the concept of microtube shape-engineering will constitute very valuable additions to future microscale soft-robotics. Here, I organized my dissertation based on four published journal papers of which I am the first/primary author

A micromanipulation setup for comparative tests of microgrippers

A micromanipulation setup allowing comparative tests of manipulation micro tools has been developed. Repeatability measurements of positioning as well as optimization of manipulation conditions can be run with parts of typically 5 to 50μm over a large set of parameters including environment conditions, substrate and tip specifications, and different strategies (robot trajectories at picking and releasing time). The workstation consists of a high precise parallel robot, the Delta3, to position the gripper, linear stages to place the parts in the field of view and two microscopes for the visual feedback and position measurement. The setup is placed in a chamber for controlling relative humidity and temperature. An interface was developed to integrate every kind of tool on the robot. Automated operations and measurement have been carried out based on localization and tracking of micro objects and gripper. Integration of micro tools was successfully accomplished and comparative tests were executed with micro tweezers. Sub micrometer position repeatability was achieved with a success rate of pick and pick operations of 95%

The Role of MEMS in In-Vitro-Fertilization

The assisted reproduction has been considered a viable solution for the infertility of humankind for more than four decades. In-Vitro-Fertilization (IVF) is one of the most successful assisted reproduction techniques, where the reproductive cell of the female partner is fertilized outside of her body. Initially, the IVF process has been conducted manually by an experienced embryologist. However, even with a highly experienced individual, the operation had extremely lower success rates due to the limited control in environmental conditions and the requirement of precise movements. Therefore, to address this technological deficit, the feasibility of the mechatronics devices for IVF procedures has been investigated. Among the different mechatronics concepts, micro-electromechanical system (MEMS) technologies have been gradually attracted to the IVF process and improved its capabilities. The purpose of this paper is to present a brief overview of the role of MEMS technologies in IVF. The article classifies the MEMS technologies in IVF based on their application in order to emphasize its contribution. In addition, the article extensively discusses the state-of-the-art mechatronic techniques utilized in Intracytoplasmic Sperm Injection (ICSI), one of the most popular techniques used in IVF. This review article expects to become extremely beneficial for the engineering researchers new to this field who seek critical information on IVF in simple terms with highlights on the possible advancements and challenges that may emerge in the future

Hybrid Microfluidic Devices For On-Demand Manipulation and Screening of Neurons and Organs of Small Model Organisms

Caenorhabditis elegans and Drosophila melanogaster are widely used model organisms for neurological and cardiac studies due to their simple neuronal and cardiac systems, genome similarity to humans, and ease of maintenance in laboratories. However, their 50m-1mm sizes and continuous mobility impede their precise spatiotemporal manipulation, thereby, reducing the throughput of biological assays. By integrating glass capillaries into microfluidic devices and using 3D-printed fixtures for precise control, we have developed hybrid lab-on-a-chip devices to facilitate the processes of animal manipulation and stimuli control, using modules for single-organism selection, orientation, imaging and chemical stimulation. These microdevices enabled us to manipulate organisms individually and to orient them at any desired direction for imaging purposes. The applications of these hybrid microdevices were demonstrated in the optical and fluorescent imaging of C. elegans cells as well as cardiac screening of Drosophila larvae. This technique can be applied in fundamental biology, toxicology, and drug discovery

Cytotoxicity assay automation

The design and construction of a system to automatically test HLP antigens are described. Major efforts were made to test and evaluate the performance of such a system, and compare its performance with nonautomatic tissue typing techniques. The system is based on the fluorochromatic cytotoxicity assay. Results show the system will work but is subject to malfunctions after a few samplings, and poses problems in showing correctly the necessary readings

Towards Feedback Controlled Droplet Microfluidic Platforms

Microfluidics, the manipulation of nanoliter to microliter volumes of fluids, can give important new capabilities to researchers in biology, chemistry, material science, and medicine. Broadly, current methods can be classified into passive and active approaches. Passive methods use physical properties and microfluidic geometry whereas active methods use external perturbations to drive desired behaviour. However, passive methods require expertise and skill, and active methods complicate fabrication, require large support systems, or are not congruent with many applications. These limitations make microfluidics practically inaccessible to many researchers. Unlike these approaches, the application of feedback control may provide users with a practical and simple way to use microfluidics. Through feedback, a controller manages the operation of a microfluidic chip without needing complicated fabrication, large support systems, and in a way that can be used in a wider set of applications. State-of-the-art feedback-controlled microfluidic (FCM) devices have several shortcomings. First, typical microfluidic chips used in these devices are simple single or double T-Junctions. Such simple chips have few degrees of freedom thus limiting how many channels can be controlled concurrently. Secondly, feedback techniques, predominantly based on optical microscopes, are bulky and costly thus incongruent with FCM applications which require compact and low cost sensing. Third, a modeling approach based on an electrical analogy (Modeling channels through resistive, capacitive, and inductive elements) leads to untenable models. Fourth, Linear Quadratic Regulator (LQR) based control laws saturate unidirectional pumps. Finally, current FCM methods necessitate significant operator interaction, which is undesirable. To improve FCM methods, this dissertation conceives a new type of chip topology with greater degrees of freedom. Secondly, a new feedback source based on lensless microscopy is developed and validated. Third, a simplified modeling approach is validated. The simplified model is used as the basis for a Model Predictive Controller (MPC). Finally, these subsystems are combined to develop a system that can generate and manipulate droplets autonomously. These developments work towards making FCM, and thus microfluidics, more accessible to the wider scientific community

Enabling Practical and Accessible Automatic Droplet Microfluidics Platforms

Droplet microfluidics has emerged as an innovative technology enabling high-sensitivity, high-resolution chemical and biological analyses via precise manipulation of picoliter-to-microliter fluid droplets. The ideal end goal of this technology is a general-purpose droplet microfluidics platform (DMP) composed of simple building blocks or modules that can be configured to perform arbitrary manipulations and analyses of individual droplets autonomously, returning desired outputs (e.g. nanoparticle synthesis) or insights (e.g. heavy metal detection) to the end-user. Although numerous innovations in droplet manipulation have emerged in the literature, most existing techniques --- broadly categorized as passive vs active --- optimize for a single application and act on continuous droplet trains, hence are difficult to generalize to arbitrary manipulation of individual droplets. Passive techniques rely on specific microfluidic chip geometries to be designed by a skilled user to perform a fixed sequence of droplet manipulations, and thus cannot be used for individual droplet control. Most active techniques embed custom actuators (electrodes, membranes, etc) within a passive system which only allows individual droplet control in localized areas, limiting the precision and resolution of droplet manipulations. A simpler and more generic technique is pressure-driven feedback control, in which droplets are sensed visually within simple passive chip geometries (e.g. T-junctions) and actuated by off-chip pumps that adjust chip inlet pressures in response to visual feedback. This approach shows that individual droplets can be stabilized and driven to arbitrary locations on-chip without the need for complex chip designs or embedded actuators, opening the door to modular automation. However, bridging the gap from this proof-of-concept to a fully automated modular platform for non-expert users requires overcoming significant practicality and accessibility challenges. Existing feedback control systems for droplet manipulation ignore time-varying behavior in the system, which gradually degrades performance and reliability, necessitating frequent manual tuning and calibration. Additionally, current software workflows require the end-user to manually set up each droplet manipulation, which does not generalize to longer manipulation sequences necessary for practical applications. Moreover, standard pressure-driven flow generation methods are either too slow and imprecise for individual droplet control, or too complex and costly to be effectively modularized. This thesis aims to address these key challenges in feedback control, software workflow, and droplet actuation to pave the way for modular automated DMPs that are practical and accessible for end-users. On feedback control, a new adaptive control system is designed to automatically perform model parameter identification online, compensating for changes in system dynamics as droplet manipulations are performed. Regarding software, a new DMP workflow is developed to allow end users to validate and execute arbitrary manipulation sequences automatically. For pressure-driven flow generation, off-the-shelf piezoelectric micropumps are evaluated as a modular, low-cost alternative to existing methods, demonstrating comparable performance in droplet manipulation

Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary