Mechanical Design and Analysis: High-Precision Microcontact Printhead for Roll-to-Roll Printing of Flexible Electronics

Flexible electronics have demonstrated potential in a wide range of applications including wearable sensors, photovoltaics, medical devices and more, due to their properties of extreme adaptability while also being lightweight and highly robust. The main challenge standing in the way of progress in this field is the difficulty of large-scale manufacturing of these flexible electronics compared to their rigid counterparts. Microcontact printing is a form of soft lithography in which an elastomeric stamp is used to transfer sub-micron scale surface patterns onto a flexible substrate via ink monolayers. The integration of microcontact printing into a roll-to-roll (R2R) system will enable continuous printing of flexible electronics and scale it up for massive manufacturing. The proposed thesis outlines a novel mechanical design for a microcontact printer which utilizes flexural motion stages with integrated position and force sensors to control the print process on a R2R system. The printhead is designed to fit the available space on the pre-installed UMass Amherst Intelligent Sensing Laboratory test table and breadboard. The R2R system includes motorized rollers for winding/unwinding the PET (polyethylene terephthalate) web substrate, and idler rollers for guiding a web through the print system. As the central element to this design, two matching plate flexures are designed on the two ends of the printer roller to control the tilting and positioning of the print roller. Flexure mechanisms rely on bending and torsion of flexible elements: this allows them to achieve much higher precision in positioning compared to conventional mechanisms which rely on surface interaction between multiple moving parts. The print resolution target for this design is 500 nm (linewidth), based on current state-of-the-art designs [1, 2]. In the initial version of the printhead design, a total of 33 parts are custom fabricated for assembly and installation in the R2R system lab setup. These include everything from the components of the print roller, specially adapted air-bearing mounts, support structures, and connectors. The design and 4 fabrication process for every component is outlined here along with the functionality, as every component was designed with the system objectives and constraints in mind. Using SolidWorks simulation, FEA (finite element analysis) is performed for every part of the assembly that is subjected to stress in the real system, so that predictions can be made about the displacement of the motion stages and the frequency of vibration. These predictions are evaluated by comparation with the experimental results from tests conducted on the real system hardware and used to assess the quality of the fabricated assembly. The work performed in this thesis enables advancements in the assembly of an updated, optimized R2R system and has led to an experimentally functioning lab setup that is ripe for further improvements. Completion and calibration of this augmented R2R system will, in future, enable UMass Amherst in-house production of large-area flexible electronics which may be used in a wide range of applications, including medical sensors, solar cells, displays, and more. In addition to microcontact printing, this R2R system may also be applied to nanoimprint lithography, another contact-based print method, or integrated with inkjet printing, a non-contact method

Hidden Markov Models for Pipeline Damage Detection Using Piezoelectric Transducers

Oil and gas pipeline leakages lead to not only enormous economic loss but also environmental disasters. How to detect the pipeline damages including leakages and cracks has attracted much research attention. One of the promising leakage detection method is to use lead zirconate titanate (PZT) transducers to detect the negative pressure wave when leakage occurs. PZT transducers can generate and detect guided stress waves for crack detection also. However, the negative pressure waves or guided stress waves may not be easily detected with environmental interference, e.g., the oil and gas pipelines in offshore environment. In this paper, a Gaussian mixture model based hidden Markov model (GMM-HMM) method is proposed to detect the pipeline leakage and crack depth in changing environment and time-varying operational conditions. Leakages in different sections or crack depths are considered as different states in hidden Markov models (HMM). Laboratory experiments show that the GMM-HMM method can recognize the crack depth and leakage of pipeline such as whether there is a leakage, where the leakage is

Digital Twin for Monitoring Ergonomics during Manufacturing Production

Within the era of smart factories, concerning the ergonomics related to production processes, the Digital Twin (DT) is the key to set up novel models for monitoring the performance of manual work activities, which are able to provide results in near real time and to support the decision-making process for improving the working conditions. This paper aims to propose a methodological framework that, by implementing a human DT, and supports the monitoring and the decision making regarding the ergonomics performances of manual production lines. A case study, carried out in a laboratory, is presented for demonstrating the applicability and the effectiveness of the proposed framework. The results show how it is possible to identify the operational issues of a manual workstation and how it is possible to propose and test improving solutions

Development of innovative cross-disciplinary engineering showcase

The development of engineering education relies substantially on interactive showcases and practical knowledge. The cross-disciplinary engineering showcase is designed to be fully interactive by having user input, producing a tangible output, and to understand distinct elements from each of the engineering disciplines such as, civil, mechanical and electrical (CME). The showcase operates from the input of mechanical rotational energy by the user pedalling the exercycle. Mechanical energy is then transferred to the pump via a gear train, which converts the user input of 30 rpm to the optimal pump operating speed of 2900 rpm. Further, it is used to pump water from the lower eservoir to the upper reservoir via one of the three flow paths, which the user can select by opening or closing flow valves. Once the water reaches a given height, it then flows back to the lower reservoir via a micro-hydro generator. As a result, it generates electrical energy stored in a power bank that can be used by the user to charge a digital device. Also, the showcase has a QR code to digital media, which will provide an additional explanation/exposition of the presented engineering principles to the user/students. The aim of this project is to develop a cross- disciplinary engineering showcase to enhance student learnings by interpreting the CME engineering principles in schools, institutes, and universities

Estimating hand-grip forces causing Cumulative Trauma Disorder

Wearable sensors have garnered considerable interest because of their potential for various applications. However, much less has been studied about the Stretchsense pressure sensor characteristics and its workability for industrial application to prevent potential risk situations such as accidents and injuries. The proposed study helps investigate Stretchsense pressure sensors\u27 applicability for measuring hand-handle interface forces under static and dynamic conditions. The BendLabs sensors - a multi-axis, soft, flexible sensing system was attached to the wrist to evaluate the wrist angle deviations. In addition, the StretchSense stretch sensors were attached to the elbow joint to help estimate the elbow flexion/extension. The research tests and evaluates the real-time pressure distribution across the hand while performing given tasks and investigates the relationship between the wrist and elbow position and grip strength. The research provides objective means to assess the magnitudes of high pressures that may cause pressure-induced discomfort and pain, thereby increasing the hand\u27s stress. The experiment\u27s most significant benefit lies in its applicability to the actual tool handles outside the laboratory settings

Development of innovative cross-disciplinary engineering showcase

The development of engineering education relies substantially on interactive showcases and practical knowledge. The cross-disciplinary engineering showcase is designed to be fully interactive by having user input, producing a tangible output, and to understand distinct elements from each of the engineering disciplines such as, civil, mechanical and electrical (CME). The showcase operates from the input of mechanical rotational energy by the user pedalling the exercycle. Mechanical energy is then transferred to the pump via a gear train, which converts the user input of 30 rpm to the optimal pump operating speed of 2900 rpm. Further, it is used to pump water from the lower eservoir to the upper reservoir via one of the three flow paths, which the user can select by opening or closing flow valves. Once the water reaches a given height, it then flows back to the lower reservoir via a micro-hydro generator. As a result, it generates electrical energy stored in a power bank that can be used by the user to charge a digital device. Also, the showcase has a QR code to digital media, which will provide an additional explanation/exposition of the presented engineering principles to the user/students. The aim of this project is to develop a cross- disciplinary engineering showcase to enhance student learnings by interpreting the CME engineering principles in schools, institutes, and universities

Surface engineering by titanium particulate injection mounding

In a recent study a structural hold down component was designed and produced using the particulate injection moulding (PIM) process. The material of choice was titanium due not only to the material properties but also due to the desire to create custom made components for a state-of-the-art marine vessel. On removal from the mould the green parts were seen to have an irregular surface on the top face. The irregular surface presented no through part defects and although the surface irregularities were caused by separation of the two-phases the effect was restricted to the outer surface of the parts. In a more historic study by the author the surface properties of titanium dental implants were modified by the use of adaptive mould inserts during the moulding phase of PIM. These two contrasting studies are considered and have become the basis of a current investigation looking to engineer surface irregularities in an ordered fashion. The application of meso-machining, and additive manufacture are considered and the functionality which may arise are presented