3D printing of foams for acoustic applications

Prasansha Rastogi

Research output: ThesisPhD Thesis - Research UT, graduation UT


Polymer foams are widely used, forexample, to protect against shocks, for thermal insulation, or to reduce noisepropagation. Foams are usually produced in bulk, resulting in large slabs withhomogeneous properties yet locally polydisperse cell sizes. However, for mostapplications, gradients are highly beneficial as these allow locally tailoringthe response of the foam to mechanical compression. In this thesis, a novelfoam manufacturing technique named “Direct Bubble Writing” is explored to 3D-printfoam parts with internal density gradients, controlled cell size, and aprescribed outer shape, and their acoustic performance is tested.

The direct bubble writing technologyuses a core-shell nozzle that dispenses a stream of gas-filled liquid bubbles.As these bubbles flow down, exposure of the stream to the UV lights initiatesthe polymerization in the bubble shells on-the-fly. The bubble shells arepolymerized to hold their shape and are stacked together to produce 3D foamarchitectures. The moving axes of the printer enable one-step fabrication of3D designs accessible including hollow or solid designs with cylindrical orsquare cross-sections.

This thesis first describes the stateof the art of materials for sound transmission loss in Chapter 2. Subsequently,in Chapter 3, a range of UV-curable resins for fabrication of micro-materialsis developed, including resins based on acrylates and thiol-enes. Chapter 4describes how the direct bubble writingprocess was optimized by systematically assessing the design parameters forprinting uniform and density gradient structures. In chapter 5, the controlparameters of foam printing (e.g. the type of gas and the gas flow rate) weresystematically varied to create samples with controlled gradients. The printedfoams are tested for sound transmission loss (STL), revealing  a maximum STL of 25 dB for homogeneous foamsat frequencies around 2600 Hz. However, sandwich-inspired gradient foamsenhance the STL to exceed 60 dB for frequencies around 2400 Hz. These foamsalso exhibit broadband acoustic absorption (~0.65) for frequencies between 300and 2600 Hz. Thus, direct bubble writing is a promising platform to producecustom (gradient) design lightweight porous acoustic materials for broadbandsound transmission loss at low frequencies.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Twente
  • Venner, Cornelis H., Supervisor
  • Visser, Claas Willem, Co-Supervisor
  • Wijnant, Ysbrand H., Co-Supervisor
Award date23 Oct 2023
Place of PublicationEnschede
Print ISBNs978-90-365-5855-6
Electronic ISBNs978-90-365-5856-3
Publication statusPublished - 23 Oct 2023


  • Foams
  • Density Gradient
  • Photopolymerization
  • Direct Bubble Writing
  • Sound Transmission Loss
  • 3D Printing
  • Polymer Bubbles


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