3D printing of liquid crystal elastomers

Liquid crystal elastomers (LCEs) are a new class of soft materials which have a myriad of potential uses due to their unique properties. Direct-Ink Writing (DIW) 3D printing provides a potential method to make large and highly complex devices from LCEs, but we need to first understand precisely how to control and optimise the extent of molecular order created in 3D printed devices. Order is dictated by a plethora of material properties and printing parameters such as temperature, ink viscosity, printing speed, and nozzle geometry.<br /> In this project you will create a fluid dynamics model to understand how the molecular ordering created by the extrusion flow can be maximised in DIW printed LCE devices. The predictions of this model will be verifying against experimental tests of physically printed LCE devices.<br />

<p>Liquid crystal elastomers (LCEs) combine entropic elasticity with liquid crystal anisotropy. They possess unique and useful properties, including stimuli-response shape actuation and the capacity to dissipate large amounts of mechanical energy. These properties are widely applicable in areas spanning sensors to protective headgear. However, as yet no commercial LCE-based devices exist&ndash; a main barrier being the lack of an effective and scalable method to control molecular orientation during synthesis. Direct-ink writing (DIW) 3D printing of LCEs is one promising technology, where liquid crystal oligomers (LCO) are aligned by the extrusion flow in the nozzle and photo-crosslinked into a LCE. Ideally, the direction of printing provides control of the orientation.</p> <p>This project will investigate the detailed fluid dynamics of the extrusion process and how this couples to the molecular ordering of the LCOs/LCEs. LCOs are strongly non-Newtonian fluids with flow properties depending upon the molecular configuration, which is in turn is generated by the flow. Depending upon the student&rsquo;s interests, the project will use a combination of simplified geometric modelling and/or CFD with an appropriate constitutive equation to model the extrusion process- supplemented by experimental DIW printing of LCEs and study of their alignment probed through optical and x-ray scattering techniques.</p> <p>The overall aim of this project is to develop a mathematical model for the extrusion of LCOs in DIW in order to investigate how printing parameters such as flow rate, nozzle shape, offset distance, nozzle velocity and temperature affect liquid crystalline ordering.&nbsp; The predictions of this model will be compared to experimental results from physical printed devices characterised using a variety of structural and thermomechanical testing. The insights gained through this project will open the door to 3D printed LCE devices for soft robotic, sensing, impact absorbing and vibration damping applications.</p>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University&#39;s website</a>. Please state clearly in the Planned Course of Study section that you are applying for&nbsp;<strong><em>PHD Applied Mathematics FT</em></strong>&nbsp;and&nbsp;in the research information section&nbsp;that the research degree you wish to be considered for is <em><strong>3D printing of liquid crystal elastomers</strong></em>&nbsp;as well as&nbsp;<a href="https://eps.leeds.ac.uk/maths/staff/4035/dr-oliver-harlen">Dr Oliver Harlen </a>as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p style="margin-bottom:11px"><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p class="MsoNoSpacing">Applications will be considered on an ongoing basis. &nbsp;Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application. &nbsp;We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p>Please note that you must provide the following documents at the point you submit your application:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> <li>Funding information including any alternative sources of funding that you are applying for or if you are able to pay your own fees and maintenance</li> </ul>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p style="margin-bottom:12px"><strong>Self-Funded or externally sponsored students are welcome to apply.</strong></p> <p><strong>UK</strong>&nbsp;&ndash;&nbsp;The&nbsp;<a href="https://phd.leeds.ac.uk/funding/209-leeds-doctoral-scholarships-2022">Leeds Doctoral Scholarships</a> and <a href="https://phd.leeds.ac.uk/funding/234-leeds-opportunity-research-scholarship-2022">Leeds Opportunity Research Scholarship</a> are available to UK applicants. <a href="https://phd.leeds.ac.uk/funding/60-alumni-bursary">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p><strong>Non-UK</strong> &ndash;The&nbsp;<a href="https://phd.leeds.ac.uk/funding/48-china-scholarship-council-university-of-leeds-scholarships-2021">China Scholarship Council - University of Leeds Scholarship</a>&nbsp;is available to nationals of China. The&nbsp;<a href="https://phd.leeds.ac.uk/funding/73-leeds-marshall-scholarship">Leeds Marshall Scholarship</a>&nbsp;is available to support US citizens. <a href="https://phd.leeds.ac.uk/funding/60-alumni-bursary">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p><strong>Important:</strong>&nbsp; Any costs associated with your arrival at the University of Leeds to start your PhD including flights, immigration health surcharge/medical insurance and Visa costs are <strong>not</strong> covered under this studentship.</p> <p>Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p>

<p>For general enquiries about applications, please contact Doctoral College Admissions: e:&nbsp;<a href="mailto:maps.pgr.admissons@leeds.ac.uk">maps.pgr.admissons@leeds.ac.uk</a>&nbsp;</p> <p>For questions about the research project contact Dr Oliver Harlen: e: <a href="mailto:o.g.harlen@leeds.ac.uk">o.g.harlen@leeds.ac.uk</a><br /> &nbsp;</p>