µCT‐Based Topography Analysis of Inaccessible Surfaces Exemplified by a Biofouling‐Covered Plastic

Abstract

Dedicated to Prof. Dr. rer. nat. Ju ¨rgen Caro on the occasion of his 70th birthdayThe measurement of surface topographies is usually restricted to surfaces that are directly accessible to tactile or optical sensing. With this paper, the application of micro-computed tomography to measure characteristics of surfaces that are covered by solid films and thus not directly accessible is demonstrated. The method is first validated by comparative measurements of a plastic sample with mCT and conventional optical profilometry. Afterwards, the mCT-based method is successfully applied to a polyhydroxybutyrate plastic sample covered by biofouling after exposure to marine environment, providing insight into the degradation processes.

Plastic Fruit Stickers in Industrial Composting─Surface and Structural Alterations Revealed by Electron Microscopy and Computed Tomography

“…Similar mechanisms of microplastic degradation have been demonstrated by micro-CT analyses of a biodegradable PHB sample exposed to a marine environment for several months 32 and an unspecified microplastic particle collected in the North Atlantic. 53 Both samples were completely covered with a biofilm consisting of a variety of microorganisms.…”

“…These cracks extended to a depth of about 600 μm. In addition, an increase in surface roughness, due to disintegration events, was observed compared to freshly manufactured PHB . Similar cracks, several hundred micrometers deep, were also observed on the unidentified microplastic particle, which was exposed to seawater.…”

“…Another reason for the high pore volumes reported in our study compared to other studies could be the more sensitive technical settings of the CT imaging. The voxel sizes of the earlier studies were 5.61, 3, and 1.7 μm/voxel, i.e., significantly larger than the voxel sizes used here for our nano-CT (<0.13 μm/voxel) and micro-CT (<0.75 μm/voxel) images of the stickers. The finer voxel sizes allow more detailed structures to be seen, although the imaging of smaller areas includes the risk of large cracks with a length of up to 600 μm being overlooked.…”

“…The voxel sizes of the earlier studies were 5.61, 3, and 1.7 μm/voxel, i.e., significantly larger than the voxel sizes used here for our nano-CT (<0.13 μm/voxel) and micro-CT (<0.75 μm/voxel) images of the stickers. The finer voxel sizes allow more detailed structures to be seen, although the imaging of smaller areas includes the risk of large cracks with a length of up to 600 μm being overlooked. To confirm the effects of composting on the fruit stickers, FTIR spectra of the stickers were acquired in addition to SEM and CT analyses.…”

“…Both methods are established techniques in a variety of scientific fields − but are rarely used for plastic analyses. Bittner and Endres for instance successfully applied micro-CT imaging to reveal surface changes in a polyhydroxybutyrate (PHB) plastic sample covered by biofouling after exposure to a marine environment. Nano-CT, which is capable of achieving voxel resolution in the submicrometric range, was applied to reveal structural changes of wood–plastic composites after exposure to different environmental conditions. − A combination of the methods mentioned above will for the first time allow the detection of surface as well as structural changes of the composted stickers.…”