1
00:00:05,597 --> 00:00:07,680
LORNA GIBSON: So I think
one of the special things

2
00:00:07,680 --> 00:00:09,910
about this course
and about my kind

3
00:00:09,910 --> 00:00:11,616
of research on
cellular materials

4
00:00:11,616 --> 00:00:13,490
is that I spend a fair
amount of time talking

5
00:00:13,490 --> 00:00:15,630
about materials in nature.

6
00:00:15,630 --> 00:00:18,960
So I talk about wood,
for instance, and what

7
00:00:18,960 --> 00:00:21,320
it is about the cellular
structure that gives rise

8
00:00:21,320 --> 00:00:23,950
to the density dependence
of wood properties

9
00:00:23,950 --> 00:00:26,220
and the anisotropy
in wood properties.

10
00:00:26,220 --> 00:00:29,140
I talk about
trabecular bone, and I

11
00:00:29,140 --> 00:00:32,090
talk about the structure
and properties of the bone,

12
00:00:32,090 --> 00:00:34,050
but also we do a
little bit of modeling

13
00:00:34,050 --> 00:00:38,090
on how you might look at
bone loss and osteoporosis.

14
00:00:38,090 --> 00:00:40,370
So if you lose a certain
fraction of the bone

15
00:00:40,370 --> 00:00:42,140
density, what residual
strength would

16
00:00:42,140 --> 00:00:44,570
you expect the bone to have.

17
00:00:44,570 --> 00:00:47,500
We have a project
on bamboo right now.

18
00:00:47,500 --> 00:00:49,210
We talk about the
structure of bamboo.

19
00:00:49,210 --> 00:00:50,810
Bamboo is actually a grass.

20
00:00:50,810 --> 00:00:55,590
And this is a Chinese species
of bamboo called moso bamboo,

21
00:00:55,590 --> 00:00:57,090
and you can see how
big this one is.

22
00:00:57,090 --> 00:01:00,274
They even get bigger, maybe
six or eight inches across.

23
00:01:00,274 --> 00:01:01,690
And what we're
interested in doing

24
00:01:01,690 --> 00:01:04,950
is making something called
structural bamboo products.

25
00:01:04,950 --> 00:01:09,020
And this is an example of a
bamboo oriented strand board.

26
00:01:09,020 --> 00:01:10,419
So the same way
people take wood,

27
00:01:10,419 --> 00:01:11,835
and they chop wood
up into strands

28
00:01:11,835 --> 00:01:15,180
and make oriented strand boards
for housing construction,

29
00:01:15,180 --> 00:01:17,810
you could, in principal, do
the same thing with bamboo.

30
00:01:17,810 --> 00:01:19,762
And we have a project
that's in collaboration

31
00:01:19,762 --> 00:01:22,220
with some colleagues at the
University of British Columbia.

32
00:01:22,220 --> 00:01:23,595
They're the ones
who are actually

33
00:01:23,595 --> 00:01:25,950
making the bamboo
oriented strand board.

34
00:01:25,950 --> 00:01:28,750
And with some architects in
England, in Cambridge, England,

35
00:01:28,750 --> 00:01:32,270
we're looking at things like how
you might modify wood building

36
00:01:32,270 --> 00:01:34,500
codes that talk about
wood structural products,

37
00:01:34,500 --> 00:01:37,202
how you would modify that for
bamboo structural products.

38
00:01:37,202 --> 00:01:38,660
And what we're
doing here at MIT is

39
00:01:38,660 --> 00:01:40,694
we're looking at the
structure of the bamboo

40
00:01:40,694 --> 00:01:42,860
and doing some modeling of
the mechanical properties

41
00:01:42,860 --> 00:01:44,450
of the bamboo itself.

42
00:01:44,450 --> 00:01:45,370
So that's one example.

43
00:01:45,370 --> 00:01:46,330
Here's another example.

44
00:01:46,330 --> 00:01:48,320
This is a bamboo laminate.

45
00:01:48,320 --> 00:01:51,986
So this is a little bit like
a glue laminated wood member,

46
00:01:51,986 --> 00:01:53,360
but in fact, this
one is made out

47
00:01:53,360 --> 00:01:54,970
of bamboo instead
of out of wood.

48
00:01:54,970 --> 00:01:57,270
So it's the same kind of idea.

49
00:01:57,270 --> 00:01:57,770
Let's see.

50
00:01:57,770 --> 00:02:00,550
We've also had a project
in the past on cork.

51
00:02:00,550 --> 00:02:03,300
So this is a cork
from a wine bottle,

52
00:02:03,300 --> 00:02:04,690
and we've looked at that.

53
00:02:04,690 --> 00:02:07,950
Cork has an unusual
mechanical property.

54
00:02:07,950 --> 00:02:10,539
You know, if you take a rubber
band and you pull on it,

55
00:02:10,539 --> 00:02:13,280
if you can make it longer this
way, it gets narrower that way.

56
00:02:13,280 --> 00:02:16,420
Well, if you load cork
in one direction, if you,

57
00:02:16,420 --> 00:02:18,430
say, pull on it
or compress it, it

58
00:02:18,430 --> 00:02:20,182
doesn't get any
wider or narrower

59
00:02:20,182 --> 00:02:21,140
in the other direction.

60
00:02:21,140 --> 00:02:23,180
It just stays the
same kind of size.

61
00:02:23,180 --> 00:02:25,070
And you can show
that that's related

62
00:02:25,070 --> 00:02:26,590
to the structure of the cells.

63
00:02:26,590 --> 00:02:28,860
The cells are like
little bellows,

64
00:02:28,860 --> 00:02:30,360
or like a little concertina.

65
00:02:30,360 --> 00:02:32,494
So you can imagine if you
have a little concertina,

66
00:02:32,494 --> 00:02:34,410
and you push on it this
way, it doesn't really

67
00:02:34,410 --> 00:02:36,410
get any bigger that way
or smaller that way.

68
00:02:36,410 --> 00:02:37,810
It just stays the
same dimension.

69
00:02:37,810 --> 00:02:39,768
And the cork cells look
a little bit like that,

70
00:02:39,768 --> 00:02:41,160
and that's why they do that.

71
00:02:41,160 --> 00:02:43,360
So we have all these
natural materials.

72
00:02:43,360 --> 00:02:45,690
We talk a little about
the hierarchical structure

73
00:02:45,690 --> 00:02:46,430
in plants.

74
00:02:46,430 --> 00:02:48,750
The cell walls are
fiber composites,

75
00:02:48,750 --> 00:02:50,680
and then there's a
cellular structure.

76
00:02:50,680 --> 00:02:54,939
And plant materials have a
sort of hierarchical structure,

77
00:02:54,939 --> 00:02:56,730
with several different
levels of hierarchy,

78
00:02:56,730 --> 00:02:59,344
and we talk about that
in the class as well.

79
00:02:59,344 --> 00:03:00,760
And we talk a
little bit about why

80
00:03:00,760 --> 00:03:03,590
that makes these materials
mechanically efficient

81
00:03:03,590 --> 00:03:06,350
and how you might look
at designing engineering

82
00:03:06,350 --> 00:03:07,580
materials based on that.

83
00:03:07,580 --> 00:03:09,760
So there's a little bit of
biomimicking in the class

84
00:03:09,760 --> 00:03:11,450
as well.