Potentially Reusable Microporous Polymers Cling to Surfaces With Variable Degrees of Adhesiveness
These adhesive films utilize a microporous shape memory polymer to perform switchable, dry adhesion useful in situations requiring two or more levels of adhesion. Dry adhesives are part of the pressure-sensitive adhesives market, which analysts expect to reach $9.5 billion by 2024. Dry adhesive materials stick to surfaces without the use of any chemical substances, leaving no residue behind when removed. Such gecko feet-mimicking adhesives have many applications in cutting-edge technologies such as bionics, soft robotic fingers, and body-tissue interfaces, as well as in more common commercial products like wall hangers, bandages, labels, tapes, or automobile trim components.
Researchers at the University of Florida have produced dry adhesive films that exhibit different adhesion forces and are reusable. Manipulating the size and number of microscale pores in shape memory polymer films can vary their adhesive strength when applied to a surface. The pores can open and close in response to multiple external stimuli, allowing removal and replacement of the adhesive films.
Application
Reusable dry adhesive films that can have multiple levels of adhesive force
Advantages
- Uses a microporous shape memory polymer, enabling different adhesive forces depending on the application
- Pores open and close when put in ethanol and water respectively, allowing reuse of the films
- Sticks to surfaces via dry adhesion, leaving no residue and facilitating easy placement and removal
- Adhesive film has a photonic structure, visually indicating adhesion state via color change
Technology
These microporous shape memory polymer films perform switchable dry adhesion. Microscale pores in the polymer create an adhesive force dependent on their number, size, and whether they are open or closed. Putting the films in water and drying them closes the pores while putting them in ethanol opens the pores. Closed pores lead to weaker adhesion, and open pores lead to stronger adhesion. Depending on the necessary adhesion force, manufacturers can manipulate the microporous dry adhesion films using plasma-etching or some other processes to vary the roughness of the film’s surface. The crystal structure of the SMP films couples film adhesiveness with color so that a color change signifies a change in adhesion state.
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