PhD Position on Shear Dilatancy in Concentrated Emulsions

Passionate about the mechanics of soft solids? Join us in this PhD project to combine theoretical and numerical modeling to fill a persistent gap in understanding shear dilatancy. We're seeking a talented PhD researcher to explore and optimize models that unravel this intriguing nonlinear phenomenon!

Job description

When you twist a solid cylinder, its height spontaneously changes. This is one example of shear dilatancy, a well-known but poorly understood nonlinear effect in solid mechanics. Shear dilatancy occurs in biopolymer gels, pastes, foams, and numerous other types of soft matter. Despite its ubiquity, we cannot reliably predict the amplitude or even the sign of the effect – most materials expand, but some contract. The key challenge is to identify a necessary and sufficient set of physical mechanisms responsible for shear dilatancy in soft solids.

Recently, experiments revealed that concentrated emulsions can display positive or negative shear dilatancy, depending on how strongly droplets attract their neighbors. This is an exciting discovery, both because systems where shear dilatancy changes sign are rare, and because attraction strength can be tuned in the laboratory. Therefore emulsions present an exciting new testbed in which to unravel the origins of shear dilatancy.

You will exploit this opportunity by

• Developing hypotheses for the origins of shear dilatancy in concentrated emulsions and related dense disordered solids.
• Incorporating these hypotheses in a novel mechanical model. Your model will build on techniques from continuum solid mechanics, along with critical scaling relations from statistical physics.
• Performing molecular dynamics/DEM simulations of attractive emulsions to validate your predictions. Emulsions will be modelled as discrete collections of soft, non-Brownian particles with a repulsive core and an attractive shell. This same model has previously been used to study the jamming transition in emulsions, foams, and granular media.

The primary output of your research will be a constitutive relation (mechanical equation of state) that connects shear dilatancy to a few essential physical properties, and uses them to predict the sign and amplitude of the dilatancy effect. It will be general enough to account for various experimental geometries and boundary conditions, and will be validated with simulations and data from benchmark experiments.

Multiphase Systems

Join a world-class research team with a strong track record in the physics of multiphase systems. You will be part of the Multiphase Systems section within the Process & Energy Department of the Faculty of Mechanical Engineering at TU Delft. This section is renowned for its innovative and fundamental research into the dynamics of complex fluid systems. You will be supervised by Dr. Brian Tighe, an expert in the mechanics of soft solids and complex fluids. His prior work focuses on rheology, (visco-)elasticity, and jamming/yielding transitions in dense disordered systems.

As a PhD candidate at TU Delft, you will conduct original scientific research, report your results in international publications and presentations, and write and defend a PhD thesis within 4 years. You will also have the opportunity to mentor BSc and MSc students and co-supervise their thesis projects. You will join a vibrant, international research community composed of highly motivated professors, postdocs, and PhD and MSc students. The Multiphase Systems section offers access to cutting-edge facilities to support your research, including high-performance computing. The environment is open and collaborative, promoting daily interaction and knowledge exchange. With minimal hierarchical barriers, you’ll benefit from strong mentorship and tailored training. Professional growth is a priority, ensuring your success in academia.

Job requirements

You need to have:

• MSc degree in physics, mechanical engineering or related fields.
• Passion for fundamental research driven by scientific curiosity.
• Demonstrated proficiency in molecular dynamics or DEM simulations, either with code you developed yourself or with open-source tools such as LAMMPS or similar. Experience with energy minimization techniques such as conjugate gradient minimization or FIRE is especially valuable.
• Excellent communication skills in written and spoken English. Strong problem-solving skills and the ability to work collaboratively in an international research environment.

The following will make you stand out:

• Coursework or research experience in continuum solid mechanics.
• Coursework or research experience in rheology and/or viscoelasticity.
• Coursework or research experience in the statistical physics of phase transitions.
• Demonstrated enthusiasm for exploring the mechanics of soft solids and solving fundamental scientific challenges.

We strongly encourage candidates from underrepresented groups to apply.

TU Delft (Delft University of Technology)

Delft University of Technology is built on strong foundations. As creators of the world-famous Dutch waterworks and pioneers in biotech, TU Delft is a top international university combining science, engineering and design. It delivers world class results in education, research and innovation to address challenges in the areas of energy, climate, mobility, health and digital society. For generations, our engineers have proven to be entrepreneurial problem-solvers, both in business and in a social context.

At TU Delft we embrace diversity as one of our core values and we actively engage to be a university where you feel at home and can flourish. We value different perspectives and qualities. We believe this makes our work more innovative, the TU Delft community more vibrant and the world more just. Together, we imagine, invent and create solutions using technology to have a positive impact on a global scale. That is why we invite you to apply. Your application will receive fair consideration.

Challenge. Change. Impact!

Faculty Mechanical Engineering

From chip to ship. From machine to human being. From idea to solution. Driven by a deep-rooted desire to understand our environment and discover its underlying mechanisms, research and education at the ME faculty focusses on fundamental understanding, design, production including application and product improvement, materials, processes and (mechanical) systems.

ME is a dynamic and innovative faculty with high-tech lab facilities and international reach. It’s a large faculty but also versatile, so we can often make unique connections by combining different disciplines. This is reflected in ME’s outstanding, state-of-the-art education, which trains students to become responsible and socially engaged engineers and scientists. We translate our knowledge and insights into solutions to societal issues, contributing to a sustainable society and to the development of prosperity and well-being. That is what unites us in pioneering research, inspiring education and (inter)national cooperation.

Conditions of employment

Doctoral candidates will be offered a 4-year period of employment in principle, but in the form of 2 employment contracts. An initial 1,5 year contract with an official go/no go progress assessment within 15 months. Followed by an additional contract for the remaining 2,5 years assuming everything goes well and performance requirements are met.

Salary and benefits are in accordance with the Collective Labour Agreement for Dutch Universities, increasing from € 2872 per month in the first year to € 3670 in the fourth year. As a PhD candidate you will be enrolled in the TU Delft Graduate School. The TU Delft Graduate School provides an inspiring research environment with an excellent team of supervisors, academic staff and a mentor. The Doctoral Education Programme is aimed at developing your transferable, discipline-related and research skills.

The TU Delft offers a customisable compensation package, discounts on health insurance, and a monthly work costs contribution. Flexible work schedules can be arranged.

For international applicants, TU Delft has the Coming to Delft Service. This service provides information for new international employees to help you prepare the relocation and to settle in the Netherlands. The Coming to Delft Service offers a Dual Career Programme for partners and they organise events to expand your (social) network.