Suriano Raffaella, Zandrini Tommaso, De Marco Carmela, Osellame Roberto, Turri Stefano, Bragheri Francesca
Dipartimento di Chimica, Materiali e Ingegneria Chimica 'Giulio Natta', Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy.
Nanotechnology. 2016 Apr 15;27(15):155702. doi: 10.1088/0957-4484/27/15/155702. Epub 2016 Feb 29.
Atomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample-tip interactions, and a custom-made shape and dimension of the tips.
原子力显微镜（AFM）对软材料的纳米压痕是探测生物材料力学性能的有力工具。尽管在过去十年中该领域已报道了许多结果，但在研究亲水性软样品时，针尖与样品之间的粘附力会阻碍弹性模量的测量。在此，采用双光子聚合（2PP）技术制备了基于全氟聚醚的疏水性AFM针尖。疏水性2PP针尖使我们能够克服商业针尖和功能化针尖的局限性，并成功在空气中测量与医学相关的软材料的弹性模量。我们对聚二甲基硅氧烷和聚乙二醇水凝胶进行表征时获得的结果表明，与使用商业针尖进行的测量相比，在更大的测量范围内粘附力更低。还发现，通过疏水性2PP AFM针尖测量的弹性模量与使用传统技术对宏观样品测得的弹性模量相当。我们成功表明，通过这种高度通用的技术开发的疏水性AFM针尖能够研究软物质的力学性能，这得益于减少的样品 - 针尖相互作用以及定制的针尖形状和尺寸。
