Bioreceptive Material Development for an Ecological Guardrail Infill System

SymbioCitys develops ecological solutions for the built environment: nature-inclusive infrastructure, fauna-inclusive building measures, green roofs and facades, and biobased material systems. The company works at the intersection of urban ecology, material development and construction practice, together with knowledge partners including Wageningen University and Windesheim University of Applied Sciences.

SymbioCitys works from one conviction: biodiversity measures in infrastructure should not stop at compliance. A measure only counts if it is ecologically suitable, measurable, maintainable and demonstrably effective in its real context.

THE CHALLENGE

A new guardrail system is being developed for Dutch road infrastructure. Another party develops the crash-rated structure and the acoustic performance. That part is not your assignment.

SymbioCitys is responsible for one component: the ecological infill inside the system. This is a material surface that should be colonised by native mosses, lichens and similar organisms. It turns a technical roadside object into functional habitat.

The material problem is unsolved. The infill has to meet two demands that pull against each other:

1. It must survive outdoors for years. Roadsides are one of the harshest microclimates in the built environment. Rain, drought, UV, freeze-thaw cycles, wind, soiling and de-icing salt all act on the surface.

2. It must have a credible end of life. Biodegradable, circular, or otherwise demonstrably responsible. The infill should not solve a habitat problem by creating a new waste stream.

Mycelium is one possible route. It is not the assumed answer. Its moisture sensitivity and outdoor lifespan have to be weighed against alternatives. We also do not want to start from an assumed CO2-neutrality claim. Climate impact should be measured, not asserted.

THE ASSIGNMENT

You will lead the material and process research for the ecological infill. The central question: which material composition and which production process create a bioreceptive surface that stays ecologically functional outdoors for years, and has a defensible end of life?

Key design variables:

- suitability for locally native mosses, lichens and other desired colonisers;

- pH, porosity, capillary behaviour, water retention and surface roughness;

- resistance to rain, desiccation, UV, freeze-thaw cycles, wind, soiling and de-icing salt;

- use of local organic residual streams, and control of variability, contamination and unwanted organisms;

- material recipe, geometry, fixation, replaceability and scalable production;

- designed service life and end-of-life scenario, treated as one joint design tension.

Three comparison routes for the first research phase:

1. Fully biobased composite. Mycelium, lignocellulosic residual streams or cork, as the reference case for maximum biodegradability.

2. Mineral-biobased hybrid. A low-CO2 binder with local biogenic fillers or biochar, aimed at longer service life and tunable pH, porosity and moisture behaviour.

3. Demountable layered solution. A durable, reusable carrier with a replaceable bioreceptive outer layer, reducing the tension between outdoor durability and degradability.

WORK PACKAGES

Scoped for six months. The emphasis adapts to your level: a master's graduation project focuses on WP1 to WP3 and delivers tested samples; a PhD or postdoc placement covers the full programme including life-cycle assessment and production route. A three-month placement covers WP1 and WP2.

WP1 - Requirements and benchmark (weeks 1-4)

Translate ecological, technical, regulatory and end-of-life demands into a measurable requirements set. Define target coloniser species and the habitat conditions they need. Benchmark existing bioreceptive materials, greening substrates and comparable roadside products.

WP2 - Formulation and sample production (weeks 3-10)

Develop candidate recipes along the three comparison routes. Produce test samples with controlled pH, porosity, water retention and surface texture. Assess the use and pre-treatment of local organic residual streams.

WP3 - Testing (weeks 6-16)

Accelerated weathering (UV, freeze-thaw, wet-dry, salt exposure), mechanical integrity and fixation behaviour, and bioreceptivity testing through inoculation or colonisation trials. Outdoor exposure on the SymbioCitys pilot setup.

WP4 - End of life and climate impact (weeks 12-20)

Biodegradation and circular end-of-life scenarios per route. An exploratory life-cycle assessment comparing the routes on a defined functional unit.

WP5 - Production route and cost (weeks 16-24)

Scalable production process, target cost per unit, replaceability and maintenance implications. Technical specification and a roadmap towards the next TRL step.

EXPECTED OUTPUTS

- A measurable requirements specification covering ecology, durability and end of life.

- A material selection matrix comparing the three routes.

- Two or three validated formulations, with produced and tested physical samples.

- A reusable test protocol and dataset for weathering, bioreceptivity and colonisation.

- An exploratory life-cycle assessment comparing the candidate routes.

- A production and cost estimate for a scalable manufacturing route.

- A technical specification sheet and a development roadmap towards the next TRL step.

WHAT SYMBIOCITYS OFFERS

- A defined, physical research question with a real industrial application and an identified route to market.

- Workspace and making facilities: a flex desk and workshop at ZWINC in Zwolle, including 3D printers. Additional materials, equipment or lab facilities can be arranged when the research requires them.

- A running pilot setup that serves as the test object for outdoor exposure.

- Weekly substantive supervision by the SymbioCitys host.

- External sparring through the company's knowledge network, including an ongoing Wageningen University track on biodiversity in the built environment.

- Flexible hours, with desk-based work such as literature review, data analysis and LCA partly possible remotely.

- Findings that feed directly into a product in development, rather than into a report that is filed away.

HOW TO APPLY

In your application, we are most interested in two things: a short account of a material you have formulated or characterised yourself, and your first instinct on which of the three comparison routes you would prioritise, and why. A disagreement with our framing is a good opening, not a problem.

Start date and exact duration are agreed together. All InnoNext internships conclude by the end of July 2027.

INCLUSION

SymbioCitys welcomes applications from researchers of all backgrounds, nationalities and career paths. We are interested in what you can build and test, not in the route that brought you here. If you meet most of the essential requirements but not all of them, we still encourage you to apply - the material question in this project is genuinely open, and we expect to learn from whoever takes it on.

If you need any adjustment to the workspace, the schedule or the application process to participate on equal terms, let us know and we will arrange it.

Primary fields: materials science, biobased and biocomposite materials, biofabrication, chemical or process engineering, construction materials, or industrial design engineering with a materials focus.

Open to both InnoNext tracks. Deep Tech Talents (PhD candidates and postdocs) and Aspiring Innovators (students and graduates of EIT Label programmes) are equally welcome. We select on what you can build and test, rather than on your title: hands-on experience gained outside a formal research position counts as fully as academic status. Eligibility for the programme itself is set by InnoNext rather than by us.

Essential

• hands-on laboratory experience in material formulation and sample production;
• experience characterising properties such as porosity, moisture transport, pH or surface behaviour;
• ability to design and run a structured test programme and interpret results critically;
• willingness to work towards a physical, testable outcome rather than a purely theoretical study.

Workplace

The internship is based at ZWINC in Zwolle, the Netherlands. ZWINC is an innovation hub that offers a flex desk workspace and a workshop with tools including 3D printers. Additional materials, equipment or lab facilities can be arranged when the research requires them.

Fieldwork and outdoor exposure testing take place on the SymbioCitys pilot setup. Working hours are flexible, and desk-based work such as literature review, data analysis and life-cycle assessment can partly be done remotely.