Microchip with an Embedded Bio-membrane for Monitoring the Electrical
Properties of the Membrane
1Xiang
Ren,
1Kewei
Liu,
2Parkson
1
Lee-Gau Chong, Hongseok
1Dept. of Mechanical Engineering
(Moses) Noh,
1Jack G. Zhou
and Mechanics, Drexel University, Philadelphia, PA, 19104
2Dept. of Biochemistry, School of Medicine, Temple University, Philadelphia, PA, 19140
Introduction
Microchip Fabrication
Discussions
Photosynthesis is a primary mechanism to produce energy in
the plant world. Realizing artificial photosynthesis system can be an
effective way of harvesting energy (from light energy to Adenosine
triphosphate (ATP) energy) that can be used as a power source for a
variety of devices. The first step to achieve this is to create a
biomembrane that conducts photosynthesis and integrate it with a
device that facilitates harvesting the energy and monitors the
function of the membrane. We introduces a microchip with an
embedded biomembrane that enables constant monitoring of the
electrical properties of the membrane. AC voltage input
A microchip was designed and fabricated such that a
biomembrane can be installed and monitored with regard to its
electrical properties. The device consists of three components: top
chamber made of glass, bottom chamber made of silicon wafer, and
middle layer with a through-hole made of PDMS. All three layers
were bonded together using oxygen plasma treatment.
The Nyquist plot was generated for each biomembrane and an
equivalent RC circuit was produced based on the best fitting. SPICE
simulation was used to illustrate the frequency response. The Bode
plot of the triblock copolymer shows much less variation with the
frequency change indicating that the triblock copolymer is more
stable than other lipid membranes in terms of frequency response.
~
U
Capacitance
(µF/cm2)
Resistance (Ω·cm2)
Capacitance
from
literature (µF/cm2)
Resistance from
literature (Ω·cm2)
Glass
Glass
PDMS
Wafer
Dielectric properties of different membrane materials
Wafer
1.301±0.275 (n=7)
7.720±0.016(n=9)
1.138±0.050×103 (n=14)
1.263±0.203×103 (n=7)
2.71×10-1 [1]
1.2~1.96 [2]
7.3 POPC/POPS (3:1) [3]
10.8 [1]
855±490 [2]
1300 POPC/POPS (3:1) [4]
log|Z| (Z in Ω)
Fabrication process flow
The dielectric properties of planar membranes were measured
by electrochemical impedance spectroscopy.
The membrane resistance 4 x 10
and membrane capacitance
3
of the triblock copolymer were
Cmembrane
2
measured to be
Rsolution
7.720±0.016×103 Ω·cm2
1
Rmembrane
and 2.872±0.070×10-7 F/cm2
0
The values were similar
0
2
4
6
8
10
12
Re(Z)
x 10
to those found in literature.
Triblock copolymer impedance Nyquist plot
The frequency of the applied
voltage was varied from 1 MHz to 10 mHz. These dielectric
properties can be used to monitor the working status of the planar
membrane during bioreactions. The resistance and capacitance
readings are subject to change if the planar membrane breaks or
unwanted leakage occurs.
5
log|Z| (Z in Ω)
Dielectric Properties Results
(b) POPC
log|Z| (Z in Ω)
Phase angle φ (°)
(c) POPC/POPS (1:1)
5
7
10
0
5
10
4
10
3
-20
-40
-50
-60
10
2
10
f (Hz)
4
10
6
10
-70
-2
We successfully developed a microchip device with an
embedded biomembrane that enables constant monitoring of the
electrical properties of the membrane. This device will be the
foundation of our proposed artificial photosynthesis system.
References
2
0
Conclusions
The authors want to thank Centralized Research Facilities in Drexel
University, and Dr. E.Caglan Kumbur. This work was supported by
National Science Foundation CMMI-1141815 and CMMI-1300792.
-30
10
10
-2
10
Planar membrane Bode plot simulation
Acknowledgement
-10
6
10
/
We chose a triblock copolymer (poly-(2-methyloxazoline)poly(dimethylsiloxane)-poly(2-methyloxazoline)
(PMOXA-PDMSPMOXA)) as our biomembrane because it can be readily prepared in
a planar membrane form and carry membrane proteins such as
Bacteriorhodopsin (BR) and Adenosine triphosphate synthase
(ATPase) which convert green light energy into chemical energy
reserved in the form of ATP.
To compare the electrical
properties and frequency
response of the triblock
copolymer with lipid
membrane materials, we
also used two types of
lipid membranes in this
experiment:
1-palmitoyl-2-oleoyl-snChemical structure of PMOXA-PDMS-PMOXA
glycero-3-phospho-choline
triblock copolymer. R can be either (1) or (2).
(POPC) and POPC/1palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) (ratio of 1:1).
We prepared the solutions and put a droplet of each solution onto
the water surface in a petri-dish allowing it to spread to form a thin
planar membrane.
PDMS double-side molding by wafer and
glass; PDMS thin film released by acetone
and isopropanol alcohol
phase angle 6 ' ( )
Bio-membrane Materials
1.805±0.272 (n=14)
Im(Z)
Illustration of the electrochemical impedance
spectroscopy setup for a planar membrane
2.872±0.070×10-1 (n=9)
Phase angle φ (°)
Assembled microchip for membrane
impedance spectroscopy
~
PDMS thin film
U
Z  Z Re  jZ Im  ~
I
Silicon
Electrodes
Electrolyte
POPC/POPS (1:1)
(a) Triblock copolymer
impedance logjZ j ( + )
Planar membrane
POPC
Phase angle φ (°)
~
I
Triblock copolymer
-1
0
1
2
log f (Hz)
Triblock copolymer impedance Bode plot
3
4
5
6
[1] H. Choi, et al, Nanotechnology 16 (2005) S143–S149
[2] J. Lin, et al, Langmuir 26 (2010) 12054-12059
[3] R. Naumann, et al, Biosens Bioelect 17(2002)25-34
[4] K. Morigaki, et al, Biophys. J. 91 (2006) 1380-1387
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