Abstract
When compliant samples such as polymer films are scanned with an atomic force microscope (AFM) in contact mode, a periodic ripple pattern can be induced on the sample. In the present paper, friction and mechanical properties of such ripple structures on films of polystyrene (PS) and poly-n-(butyl methacrylate) (PnBMA) are investigated. Force volume measurements allow a quantitative analysis of the elastic moduli with nanometer resolution, showing a contrast in mechanical response between bundles and troughs. Additionally, analysis of the lateral cantilever deflection when scanning on pre-machined ripples shows a clear correlation between friction and the sample topography. Those results support the theory of crack propagation and the formation of voids as a mechanism responsible for the formation of ripples. This paper also shows the limits of the presented measuring methods for soft, compliant, and small structures. Special care must be taken to ensure that the analysis is not affected by artefacts.
Highlights
When scanning in contact mode, the tip of an atomic force microscope (AFM) permanently indents the sample if the stiffness of the sample is lower than the stiffness of the cantilever
AFMscan-induced ripples have been observed on films of polystyrene (PS) (Leung and Goh, 1992), polyethylene terephthalate (PET) (D’Acunto et al, 2007), poly-ε-caprolactone (PCL) (D’Acunto et al, 2007), polyvinyl acetate (PVA) (Schmidt et al, 2003a), and polycarbonate (PC) (Sun et al, 2012; Yan et al, 2014; Wang et al, 2020)
Measurements are conducted on two polymers spin-coated on glass substrates: polystyrene (PS), which is in a glassy state at room temperature, and poly-n-(butyl methacrylate) (PnBMA), which is in the transition from glassy to rubbery state and less stiff, as its glass transition temperature is close to room temperature
Summary
When scanning in contact mode, the tip of an atomic force microscope (AFM) permanently indents the sample if the stiffness of the sample is lower than the stiffness of the cantilever. The rubber sample usually relaxes back to its original state with a smooth surface once shear forces are removed Since this is in contrast to the observed properties of AFM-scan-induced ripples, the theory of Schallamach waves is not appropriate to explain the phenomenon (Schmidt et al, 2003b). The formation of cracks or voids inside the polymer bundles implies an increase of the total volume and a lower stiffness of the ripples compared to the unperturbed polymer film. This paper reports for the first time an analysis of AFM-scan-induced polymer ripples through a force volume Such a measurement yields robust quantitative results with a high spatial resolution to verify the hypothesis of formation of voids in polymer ripples. Measurements are conducted on two polymers spin-coated on glass substrates: polystyrene (PS), which is in a glassy state at room temperature, and poly-n-(butyl methacrylate) (PnBMA), which is in the transition from glassy to rubbery state and less stiff, as its glass transition temperature is close to room temperature
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
