EAGER/Collaborative Research: Solid Freeform Fabrication of a
Conceptual Artificial Photosynthesis Device
1Xiang
Ren,
1Dept.
2Hao
1
3
2
1
Lu, Qingwei Zhang, Parkson Chong, Wayne Yuan, Jack G. Zhou
of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, 19104
2Dept. of Biological and Agricultural Engineering, North Carolina State University, Raleigh, NC, 27695
3Dept. of Biochemistry, School of Medicine, Temple University, Philadelphia, PA, 19140
Bacteriorhodopsin(BR) proton pumping measurement
The main objective of this research is to fabricate an artificial
photosynthesis device that is capable of converting sunlight, CO2
and water into sugars for the production of biofuels. Solid freeform
fabrication (SFF) enhanced by high-resolution heterogeneous
printing technology was investigated to design and build this
innovative device. This device contains multi-layer interconnected
channels and micro-porous structures. This research enables
manufacturing and deployment of large-scale solar conversion
systems which not only mimic the nature process of photosynthesis
for the production of biofuels, but also make these reactions
independent of the life of nature plants.
BR is a light-driven proton pump that creates a pH gradient across
the cell membrane via a light-induced BR photocycle. This
electrochemical proton gradient is used to drive the synthesis of
ATP from ADP and Pi. The method mainly consists of incorporating
BR into triblock polymers and taking a luminescence measurement.
Photo-induced changes in intravesicular pH were measured using
pyranine as a fluorescent pH probe. Photo-induced activity was
0
measured after illumination using a 5.0 W -0.01
-0.02
light source (green LED). An excitation
-0.03
scan from 350 to 475nm at an emission
-0.04
wavelength of 511nm was performed using -0.05
-0.06
0
20
40
60
a Microplate Reader.
Time (minutes)
pH
Introduction
Heterogeneous materials printing
Illustration of the proposed artificial photosynthesis system: (a) The envisioned artificial leaf-like
device for biofuels manufacturing. Expected yield will be 10 times higher than biomass. (b)
Magnified: Multi-layers with interconnected channels and micro pours. (c) Further magnified:
heterogeneously printed structures.
By mimicking natural leaves, we will design and fabricate an
innovative architecture with multi-layer interconnected channels
and micro-porous structures to support artificial photosynthesis for
sugar production. This device will be heterogeneously printed using
a specifically designed SFF machine with multi-function nozzle array.
The technical processes of the 3Multi-AM are briefly described as
follows. Before the printing we will design the 3D multi-layer leaf in
CAD software. Then we’ll use our new developed heterogeneous
materials printing algorithm to generate sliced G-code files to
control and move the nozzle array.
CMMI-1141815; CMMI-1141830
PI: Jack G. Zhou, Wayne Yuan
Institution: Drexel University and
North Carolina State University
Materials study
Chitosan hydrogel was produced by dissolving 1.5wt% of chitosan
into 1% acetic acid. The solution was stirred at room temperature
for 6 hours, then stabilized at 4˚C overnight. It was then immersed in
liquid nitrogen (-196˚C) for one hour. The resulting micro-porous
structure was assessed under SEM.
Morphology of micro-porous chitosan produced by a liquid nitrogen freeze drying process
Table: Porosity results of 1.5wt% chitosan with and without 5wt% gelatin scaffold
(C: Chitosan; G: Gelatin; 1% acetic acid)
sample
Petri-dish
(g)
Volume
(mL)
After
gelation (g)
After
freezedrying (g)
Porous
volume
(mL)
Porosity
(%)
C1
1.644
4
5.713
1.721
4.069
0.077
0.0604
98.49
C2
1.623
4.5
6.263
1.708
4.640
0.085
0.0667
98.51
C3
1.638
5
6.626
1.730
4.988
0.092
0.0722
98.56
CG1
1.606
5
6.557
1.783
4.951
0.177
0.1315
97.37
CG2
1.604
4
5.555
1.750
3.951
0.146
0.1085
97.29
CG3
1.635
4.5
6.021
1.792
4.386
0.157
0.1166
97.41
Porousmas
Gel mass(g)
s(g)
Chitosan hydrogel can form 3D structures by printing or casting
method. For preliminary results, we used the casting method to
make a 3D leaf-like structure with inner channels. The large scale
leaf structure proves that the chitosan hydrogel can achieve 3D
fabrication of porous structure with interconnected channels.
Artificial photosynthesis light reaction
ADP→ATP
The bioluminescence assay kit was used
ATP synthase
to make measurements of ATP synthesis
ADP→ATP
BR
activity. The reaction mixture in bulk–vesicle
solutions contained BR-ATP synthase mixed
solution, ADP, KH2PO4 , and deionized water.
A 5.0W green LED was used to illustrate the
ADP→ATP
sample in order to generate a proton gradient. Triblock polymer vesicle:
H+ are
A sample of the reaction mixture was taken pumped to the inside of vesicles
every 10 minutes, and an equal volume of trichloroacetic acid was
added to stop ATP production. ATP production
was quantified by measuring the luminescence
of the sample and comparing it to a standard
calibration curve. The figure shows a clear
increase of ATP over time which confirms
ATP produced from the vesicle
the expected light reaction from vesicles.
Chitosan hydrogel leaf before (a) and after lyophilization (b,c) and the inside channel structures (c)
Conclusions
Schematic diagram of heterogeneous materials printing system
The objective of this research is to fabricate the tri-block polymer
reconstituted with BR and FoF1 ATP synthase for the light reaction of
the artificial photosynthesis device. The vesicle and planar film will
have the function of pumping H+ and creating a pH gradient, which
drives the FoF1 to convert ADP to ATP. ATP will be used in the dark
reaction for changing CO2 into sugars.
The light reaction layer will create a pH gradient which drives FoF1
ATP synthase to convert ADP to ATP. The Heterogeneous materials
printing machine can fabricate porous interconnected structures via
printing with or without light conversion vesicles. According to
materials study, chitosan is appropriate for forming porous
structure.
Acknowledgement
The authors want to thank Centralized Research Facilities in Drexel
University. This work was supported by National Science Foundation
CMMI-1141815 and CMMI-1141830.