Nature - USA (2020-08-20)

Nature | Vol 584 | 20 August 2020 | 389

the silica sol. These denser grains (Fig. 2f–i) form an interlocked particle
packing with direct particle contacts (Fig. 2j–l, Extended Data Fig. 4).
The printed objects consist entirely of hydrophobic silica aerogel,
as evidenced by solid-state nuclear magnetic resonance (NMR) and

Fourier transform infrared (FTIR) spectroscopy (Extended Data Fig. 5),

indicating that the viscosity modifier is fully washed out during the

solvent exchanges and/or supercritical drying. The contact angle with

water is 150° ± 2°. The high- and low-density aerogel phases display a

x

y

x^10 μm

y

z

Aerogel particle

MnO 2 -stained aerogel matrix

MnO 2 -enriched area

50 μm

100 101 102

0

0.02

0.04

0.06

0.08

0.10

0.12

dV

/d

w (cm g

–1 nm

–1)

Pore width, w (nm)

0 200 400 600 800

90

95

100

II, 9.1%

II, 8.8%

Weight (%)

Temperature (°C)

I, 0.9%

I, 1.7%

200 μm^10 μm 500 nm

500 μm 500 μm 200 μm

1

2

3

4

5

5 mm 10 mm 10 mm

Phase 1:

aerogel

particle

Phase 1:

aerogel

particle

Phase 2:

aerogel

matrix

a

d

ghi

ef

bcj

k

l

0 0.2 0.4 0.6 0.8 1

0

500

1,000

1,500

2,000

2,500

N^2

sorption (cm

3 g

–1)

Relative pressure

Silica aerogel particle

SP1.6 printed object

mno

35 μm

Fig. 2 | 3D-printed objects, their microstructure and selected properties.
a, A 10-layer honeycomb (ink SP1.6 (Extended Data Table 1), 410-μm conic
nozzle, 2.4 min at 15 mm s−1). b, A 33-layer lattice cube (ink SP1.3M0.9, 410-μm
conic nozzle, 8 min at 12 mm s−1; Supplementary Video 2). c, Various 3D
patterns (three layers, ink SP1.6, 250-μm conic nozzle, 1 min at 18.4 mm s−1;
Supplementary Video 3). d, Scanning electron microscopy (SEM) image of a
lattice. e, A multi-layer continuous membrane. f, Outer surface of a printed
filament. g, Interface between two filaments. h, Magnification of the
oranged-boxed region in g, showing interlocked aerogel particles (darker grey)
embedded in a low-density aerogel matrix (lighter grey). i, Magnification of the

orange-boxed region in h, highlighting the two aerogel phases. j, Tomographic

slice of a printed aerogel filament (ink SP1.6, 410 μm). k, 3D volume rendering

of the oranged-boxed area in j (98 μm × 98 μm × 234 μm), with the low-density

aerogel matrix shown (left) and removed (right). Both renderings are stacks of

720 cross-sections. l, An x–y section (98 μm × 98 μm) with the low-density

matrix removed (darker grey, cut surface of particles; lighter grey, underlaying

particle surfaces). m, N 2 sorption isotherms at 77 K. n, Pore size distribution

derived from Barrett–Joyner–Halenda (BJH) analysis (V, pore volume; w, pore

width). o, Thermogravimetric analysis. Weight change I corresponds to

adsorbed water, weight change II to trimethylsilyl groups.