TABLE 5.

Influence of surface stiffness on bacterial adhesion.

Microorganism	Surface material	Young’s Modulus	Influence on adhesion/biofilm growth	References
Bacillus and Pseudoalteromonas	Agarose hydrogels	6.6 and 110 kPa	Reduced bacterial adhesion on softer hydrogels	Guegan et al., 2014
E. coli and S. aureus	Poly(ethylene glycol) dimethacrylate (PEGDMA) and agar hydrogels	Soft: 44.05 – 308.5 kPa. Intermediate: 1495 – 2877 kPa. Stiff: 5152 – 6489 kPa.	Reduced bacterial adhesion on softer hydrogels	Kolewe et al., 2015
S. aureus	poly-N-isopropylmethacrylamide based microgel coatings	Soft: 21 ± 8 kPa. Intermediate: 117 ± 20 kPa. Stiff: 346 ± 125 kPa.	Reduced bacterial adhesion on softer microgel with lower cross-linking density	Keskin et al., 2019
E. coli and Pseudomonas sp.	PDMS	3.4–278.1 MPa	Reduced bacterial adhesion and levels of c-di-GMP when bound to the softer PDMS	Peng et al., 2019
E. coli and L. lactis	Photo-cross-linked polyelectrolyte films	30–150 kPa	Increased E. coli adhesion on softer films, no effect for L. lactis adhesion	Saha et al., 2013
S. aureus	Polyacrylamide (PAAm) and poly(ethylene glycol) dimethacrylate (PEGDMA)	0.017–0.654 kPa	Increased bacterial adhesion on softer hydrogels	Wang et al., 2016
E. coli	PDMS	0.1–2.6 MPa	Increased bacterial adhesion on softer PDMS	Song F. et al., 2017
E. coli and S. aureus	Poly(ethylene glycol) (PEG) hydrogels	Soft: 20 kPa. Intermediate: 300 kPa, Stiff: 1,000 kPa.	Increased bacterial adhesion and biofilm formation on softer surface	Kolewe et al., 2018
P. aeruginosa	PDMS	0.1–2.6 MPa	Increased bacterial adhesion and levels of c-di-GMP when bound to the softer PDMS	Song et al., 2018
P. aeruginosa E. coli	PDMS	4.52 ± 0.09–0.06 ± 0.001 MPa	Increased bacterial adhesion on softer PDMS	Straub et al., 2019
E. coli, P. aeruginosa, and S. epidermidis	PDMS	64.2–2326.8 kPa	Increased bacterial adhesion on softer PDMS	Pan et al., 2020
E. coli	PDMS	0.26 ± 0.01 and 124 ± 36 kPa	Similar initial levels of bacterial adhesion on soft and stiff surfaces but increased bacterial adhesion strength on softer surface	Siddiqui et al., 2019