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Supporting Information
Stretchable Graphene Thermistor with Tunable
Thermal Index
Chaoyi Yan, Jiangxin Wang, Pooi See Lee*
School of Materials Science and Engineering, 50 Nanyang Avenue, Nanyang Technological
University, Singapore, 639798
*Address correspondence to [email protected].
Figure S1. Resistance comparison of highly conductive AgNW electrodes and resistive
graphene channel. (a) Resistance variations of AgNW and graphene within 0-50% strains.
Graphene resistance was measured at 30 °C and AgNW resistance was measured at room
temperature (~25 °C). (b) Plot showing the ratio between R(Graphene) and R(AgNW). The
resistance of graphene is ~6 orders of magnitude higher than that for AgNW electrodes, thus
the contribution of AgNW electrodes to overall device resistance is negligible.
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Figure S2. (a,b) Cross-sectional schematic illustrations of the device layouts before and after
being embedded into PDMS substrate. (c,d) SEM images of the AgNW-graphene junction
area before embedding. Graphene layer was on top of AgNW electrodes after filtration so
that the electrodes can be exposed after embedding for electrical connection.
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Figure S3. The dependence of device resistance on temperature is non-linear, as revealed by
the attempted linear fitting results in (a). A good linear fitting between ln(R) and 1/T was
obtained, as shown in (b).
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Figure S4. (a) Cross-sectional schematic diagram of the stretched thermistor device on glass
slide. The device was first fixed at one end, then stretched to desire strain and fixed at the
other end using binder clips. (b,c) Image of the thermistor on glass slide substrate at 0% and
50% strains, respectively.
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Figure S5. I-V curves of the thermistor device at various strains from 0% to 50%. The
vertical axes were set at the same scale for comparison. The temperature range was 30 °C to
100 °C (step 5 °C) at all strains as indicated in (a). Calculated resistance variations with
temperature at different strains are shown in Figure 4a, main text.
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Figure S6. Thermal index variation upon repeated stretching. (a) Measured thermal index
after 1, 50 and 100 stretching cycles to 50% strain. The thermal properties of graphene
thermistors are stable and can return to initial values after mechanical stretching. (b)
Comparison of thermal index at relaxed state (after repeated stretching) and those at stretched
states.
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Figure S7. Schematic illustration of the rate limiting step in response behavior measurements.
The graphene detection channel is exposed on top of the PDMS substrate and thus is in direct
contact with the cool air, resulting in a fast response process. However, when the temperature
perturbation was stopped and the thermistor was allowed to recover, the temperature of the
graphene channel experienced a much slower recovering process due to the low thermal
conductivity of PDMS substrate.
PDMS
AgNW AgNWGraphene
Cool Air (~25 °C)
Heating Stage (50 °C)
Direct contact with
graphene channel
Fast heat transferGlass Slide
Slow heat transfer
(rate limiting step)