FFM images of PC12 living cells acquired at a constant force of 50 pN.

<p>Scan area  = 90×90 a) Sample topography, b) force between the tip and the sample (error), c) force gradient and d) damping factor at 2.25 kHz. e) Sample topography, f) force (error), g) force gradient and h) damping factor at 13.25 kHz.</p

Spectroscopy of the PC12 in liquid buffer.

<p>Force gradient (a), damping factor (b) and dissipative force (inset) as a function of the excitation frequency. Excitation frequencies: Blue  = 1.13 kHz, Red  = 5.13 kHz, Green  = 7.13 kHz, Black  = 11.13 kHz. The error bars are shifted upward for clarity.</p

FFM images of PC12 living cells acquired at a constant force of 500 pN and 1 nN.

<p>In the images at 500 pN constant force (a,b,c,d) the scale bar is 30 a) Sample topography, b) force between the tip and the sample (error), c) force gradient and d) damping factor. In the images at 1 nN (e,f,g,h), the scale bar (a,e) is 30 e) Sample topography, f) force (error), g) force gradient and h) damping factor.</p

Indentation static curve on a PC12 (blue) fitted with equation (3) (red).

<p>The fit of the soft outer layer of the cell, referred as “brush layer” in the text, is in green. The tip is modeled as a four-sided pyramidal indenter. The Young modulus extracted is 1070 Pa using a Poisson ratio equal to 0.5 and Inset: Histogram of the distributions of the PC12 Young's modulus. The quasi-static value is 1.1 kPa±0.3 kPa.</p

Analysis of the PC12 elastic properties through indentations curves.

<p>a) Force gradient as a function of the tip indentation. a) Excitation frequency  = 1.13 kHz, b) Excitation frequency  = 5.13 kHz, c) Excitation frequency  = 7.13 kHz, d) Excitation frequency  = 11.13 kHz. The lines in orange are the experimental linear fit of the cell elasticity using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101687#pone.0101687.e047" target="_blank">equation (4</a>).</p

Spectroscopy of the glass in liquid buffer.

<p>Force gradient (a) and damping factor (b) as a function of the excitation frequency. Excitation frequencies: Blue  = 1.11 kHz, Red  = 3.11 kHz, Green  = 9.11 kHz, Black  = 11.11 kHz.</p

PC12 living cells imaged in conventional contact mode.

<p>Scale bar  = 30 Several cells of different shapes are here imaged.</p

Frequency dependence of the PC12 Young's modulus.

<p>Frequency dependence of the PC12 Young's modulus.</p

Directed Growth of Virus Nanofilaments on a Superhydrophobic Surface

The evaporation of single droplets of colloidal tobacco mosaic virus (TMV) nanoparticles on a superhydrophobic surface with a hexagonal pillar-pattern results in the formation of coffee-ring type residues. We imaged surface features by optical, scanning electron, and atomic force microscopies. Bulk features were probed by raster-scan X-ray nanodiffraction. At ∼100 pg/μL nanoparticle concentration, the rim of the residue connects to neighboring pillars via fibrous extensions containing flow-aligned crystalline domains. At ∼1 pg/μL nanoparticle concentration, nanofilaments of ≥80 nm diameter and ∼20 μm length are formed, extending normal to the residue-rim across a range of pillars. X-ray scattering is dominated by the nanofilament form-factor but some evidence for crystallinity has been obtained. The observation of sheets composed of stacks of self-assembled nanoparticles deposited on pillars suggests that the nanofilaments are drawn from a structured droplet interface