shown in Fig. 1D, the normal directions of the
ossicles are primarily oriented along the [111]
direction of the diamond microlattice. The
m-CT projection images and corresponding
3D-FFT patterns further demonstrate that
the diamond microlattice structure is con-
served in ossicles from both the aboral and oral
sides (Fig. 1M, figs. S10 and S11, and movie S5),
and the lattice constant is 29.2 to 34.2mm
(corresponding to a branch lengthlof 12.6 to
14.8mm) (fig. S12 and table S1). By using a
customized cellular network analysis algorithm
( 10 , 11 ), we further show that structural param-
eters such as branch length and thickness
exhibit spatial variations within individual
ossicles, as demonstrated in figs. S13 to S17
and tables S2 and S3.
Defects such as dislocations are ubiquitous
in atomic crystals and play significant roles in
controlling material properties ( 12 ). We inves-
tigated the structural defects at the lattice level
within ossicles and compared them with known
classes of defects in atomic crystals with the
cubic diamond symmetry (e.g., diamond and
silicon) ( 12 ). Careful examination of them-CT
slices and SEM images of fractured ossicle
surfaces reveal the presence of dislocation-like
lattice defects (Fig. 2, A and B). In addition, we
identified two prominent dislocation types in
the ossicles, namely 60° dislocations and screw
dislocations(Fig.2,CtoH),whicharealsothe
primary dislocation types found in atomic
diamond crystals ( 12 – 15 ). For the 60° disloca-
tion, the Burgers vector (b60°) and the disloca-
tion line direction (x60°) are oriented along
different <110> directions (e.g.,b60°¼ 1 =2 01½ 1 ,
x60°¼½ 10 1 ), making a 60° angle betweenb60°
andx60°( 13 , 14 ). Similar to atomic diamond
crystal structures, because of the presence of
two inequivalent families of {111} planes, the
glide set and shuffle set, two types of 60°
dislocations are observed, the G-type and the
S-type, respectively, depending on where the
inserted extra plane terminates (Fig. 2, F and
G) ( 14 , 15 ). In addition, the branches on the
“compressive”and“tensile”sides of the 60°
dislocation cores have reduced and increased
lengths, respectively, whereas the branch thick-
ness remains relatively uniform (Fig. 2, F and
G). For the screw dislocations, the Burgers
vector (bs) and the dislocation line direction
(xs) are along the same <110> direction (e.g.,bs=
1/2[011],xs= [011]), which form the classic
zig-zag-like pattern of screw dislocations whenviewed normal to a 11ðÞ 2 plane (Fig. 2E).
Although the core structure of the screw dis-
locations exhibits multiple different config-
urations in atomic diamond crystals ( 13 , 16 ),
our analysis reveals that the dislocation core
in the ossicles’diamond microlattice resem-
bles an undissociated screw dislocation in the
shuffle set with kinks (Fig. 2H) ( 17 , 18 ). Fur-
ther structural analyses of dislocations in ossicles
are shown in figs. S18 to S23.
At the whole-ossicle level, the microlattice
dislocation density is estimated to be in the
range of 100 to 1200 cm–^2 , corresponding to a
normalized density of 0.001 to 0.011 (measure-
ment based on eight ossicles randomly chosen
from both aboral and oral sides; see also table
S4, fig. S24, and materials and methods). This
result is considerably higher than the disloca-
tion density in natural and synthetic single-
crystalline diamonds, which is typically <10–^6
( 19 , 20 ). Beyond the ossicle example described
here, lattice dislocations are frequently en-
countered in other highly periodic biological
materials, ranging from the spiral-like comb
geometries of stingless honey bees ( 21 ) to the
damage-tolerant microlaminate architecture
of bivalve nacre ( 22 , 23 ).SCIENCEscience.org 11 FEBRUARY 2022•VOL 375 ISSUE 6581 649
D E[111] 100 μm 50 μm 200 μm 50 μm 50 μmb =1/2[011]60°
dislocationScrew
dislocation50 μm 50 μml (10-20 μm) t (3-5 μm) l (10-20 μm) t (3-5 μm)50 μm(1) (2)(3) (4)Node type: N-3 N-4 N-5l (10-20 μm)(1) (2)(3) (4)(1) (2)(3) (4)sA B C D EFGH[111]
[112] [110][111]
[101] [121]b 60°=1/2[011][121][111] b 60°b 60° b 60°[121][111] b 60°b 60° b 60°[112][110][111]
[110] [112]b sb s[111]
[112] [110]Fig. 2. Lattice dislocations in the ossicleÕs diamond-TPMS structure.
(A)m-CT reconstruction slice along the (111) plane, with dislocation-like defects
highlighted. (B) SEM image of a dislocation-like defect on the fracture surface
of an ossicle. (C) Reconstructed volume of an ossicle with representative
60° and screw dislocations highlighted. (DandE) Magnified views of 60° (D) and
screw dislocations (E) extracted from (C). (FandG) 60° glide (F) and shuffle
dislocations (G) in the ossicles: (1) 2D models, (2)m-CT reconstructions of the
dislocation core structures, and corresponding maps of (3) branch lengthland
(4) thicknesst. The five-node ring in F(2) is shaded in green and the seven-node
ring in F(2) and the eight-node ring in G(2) are shaded in cyan. Burgers vector
b60°¼ 1 =2 01 1
.(H) Shuffle screw dislocation with kinks: (1) 2D model,
(2)m-CT reconstruction of the observed dislocation core structure, (3) map of
branch lengthl, and (4) corresponding 3D connectivity diagram from an
individual ossicle. The branches in the Burgers circuit are colored in red.
Burgers vectorbs= 1/2[011]. The N3, N4, and N5 nodes are colored in green,
red, and blue for (F) to (H), respectively.RESEARCH | REPORTS