Figure 4.1
 
75
(a)
(b)
5 mm
5 mm
5 mm
(c)
(d)
(e)
20 µm
20 µm
BNC
Gelatin
BNC­gelatin
Tough Bacterial Nanocellulose Hydrogels Based on the Double-Network
Figure 4.1
Pictures. show. the. gel. images. (a,. b,. c),. scanning. electron. microscopy. (SEM). images. (d). and.
wide-angle.X-ray.diffraction.(WAXD).patterns.(e).of.BNC,.gelatin,.and.BNC-gelatin.DN.gels..
(a)  Before. compression.. (b). During. compression.. (c). After. 10. min.. of. compression.. (d). SEM.
images.of.the.stratified.structure.of.EC.and.BNC-gelatin.DN.gel..(Reproduced.with.permission.
of.Nakayama.et.al..2004.)
Gelatin. is. a. polypeptide. derived. from. an. extracellular. matrix—collagen..
Gelatin.gel.can.keep.water.and.recovers.from.repeated.compression..Gelatin.
gel.is.brittle.and.is.easily.broken.into.fragments.under.modest.compression.
of.0.1.MPa.(Figure 4.1,.column.2)..In.contrast,.BNC-gelatin.DN.gel.can.hold.
water.even.under.pressure.as.high.as.3.7.MPa.and.completely.recovers.its.
original.shape.after.repeated.compression.(Figure 4.1,.column.3).
The. typical. compressive. stress–strain. curves. of. BNC,. gelatin,. and. their.
composite. BNC-gelatin. DN. gels. are. shown. in. Figure  4.2a.. The. compression. is. applied. in. a. direction. vertical. to. the. stratified. structure. of. BNC.
and. BNC-gelatin. gels.. The. gelatin. gel. and. BNC-gelatin. DN. gel. were. prepared. from. a. gelatin. solution. of. 30%. concentration. in. the. presence. of.
1 M.1-ethyl-3-(3-dimethylaminopropyl).carbodiimide.hydrochloride.(EDC).
The.BNC-gelatin.DN.gel.shows.a.different.stress–strain.profile.compared.
with.those.of.individual.BNC.and.gelatin.gels..The.composite.gel.shows.a.