Liquid imaging

Atomic force microscopy (AFM) enables the visualisation of biopolymers in their native hydrated state [ 1,2] in liquid, in a partially dehydrated state in air, in a dehydrated state in an ultra-high vacuum, or in their frozen state with cryogenic AFM. Liquid imaging is often preferred where there is a desire to observe dynamic events, or acquire more biologically relevant data [1,3-6]. The data obtained from AFM may also be more biologically relevant, as no... 

There are many advantages to using liquid AFM to characterise biopolymers these advantages include the elimination of capillary forces (responsible for tip-adhesion) and reductions in van der Waals forces [11,51,61,62]. liquid imaging also allows the degree of biopolymer immobilisation to be adjusted by controlling substrate-polymer interactions [3,5,63,64]. 

One more application area is composite materials where one wants to investigate the 3D structure and/or reaction to external influences. Fig.3a shows a shadow image of a block of composite material. It consists of an epoxy matrix with glass fibers. The reconstructed cross-sections, shown in Fig.3b, clearly show the fiber displacement inside the matrix. The sample can be loaded in situ to investigate the reaction of matrix and fibers to external strain. Also absorption and transmission by liquids can be visualized directly in three-dimensions. This method has been applied to the study of oil absorption in plastic granules and water collection inside artificial plant grounds. 

Figure Al.7.14. 3.4 mn x 3.4 mn STM images of 1-docosanol physisorbed onto a graphite surface in solution. This image reveals the hydrogen-bonding alcohol molecules assembled in lamellar fashion at the liquid-solid interface. Each bright circular region is attributed to the location of an individual hydrogen...

One class of large molecules that was investigated relatively early was liquid crystals [37, 38], and in particular the group 4-n-alkyl-4 -cyanbiphenyl (mCB). These molecules fonu a highly crystalline surface adlayer, and STM images clearly show the characteristic shape of the molecule (figure B 1.19.8). 

---