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In this study, a new preparation method is developed to include thermochromic complex ions in polydimethylsiloxane (PDMS) as a stretchable composite. Ethylene glycol (EG) droplets down to the nanometer scale were dispersed using a reverse micelle method to form a stable suspension in PDMS precursor solution. After curing, the EG nanodroplets were well encapsulated in the cured PDMS elastomer. The EG/PDMS composite exhibited great stability after thermal heating at 100 °C for 2 hours. The deformable liquid droplets helped maintaining the composite structures under severe stretching conditions, and thus the stretched composite exhibited great transparency without any fractures or delamination. Ionic dyes, such as methylene blue and Congo red, can be added in the EG droplets to color the composite. Moreover, complex ions with thermochromic properties can also be used in the composite. Upon thermal heating, the reconfiguration of the complex ions in the liquid dispersed phase led to obvious color changes, and the color remained unchanged up to 50% tensile strain after more than 1000 stretch cycles.

In this work, the dependence of effective Young's modulus on the thickness of suspended graphene was confirmed through a drop impingement method. Large area suspended graphene (LSG) layers with a diameter of up to 400 μm and a nanometer thickness were prepared through transferring chemical vapor deposition grown graphene from copper substrates. 4, 8, and 12-layer LSG samples were found to be crumpled yet defect-free. The mechanical properties of LSG were first studied by observing its interaction with impinging droplets from an ink-jet nozzle. First, the effective Young's modulus was calculated by fitting the instant deformation captured by high speed photography within microseconds. Next, droplets deposited on LSG caused deformation and generated wrinkles and the effective Young's modulus was calculated from the number of wrinkles. The above methods yielded effective Young's modulus values ranging from 0.3 to 3.4 TPa. The results from these methods all indicated that the effective Young's modulus increases with the decreasing thickness or size of suspended graphene layers. Moreover, the crumpled LSG yields higher effective Young's modulus than ideal flat graphene. These comprehensive results from complementary methodologies with precise LSG thickness control down to the nanometer scale provide good evidence to resolve the debate on the thickness dependence of mechanical strength for LSG.

In this study, a non-enzyme glucose fuel cell is assembled and shows high energy density in neutral solution at moderate temperature. The anodic material, graphene sheets grafted with platinum and palladium (PtPd/G), is prepared by polyol method to oxidize glucose. The cathode material, nitrogen-doped graphene oxide nanoribbons (NGONR) is prepared by a microwave process, and shows great oxygen reduction capability in neutral cerebrospinal fluid (CSF) solution. After cell assembly, test results show that the performance of the glucose fuel cell is significantly affected by oxygen concentration, glucose concentration and operating temperature. Compared with the enzyme glucose fuel cell, the non-enzyme glucose fuel cell can generate power not only at room or human body temperatures, but within a temperature range from 5 to 80 °C. The cell power density increases with increasing operating temperature. The assembled fuel cell can produce a maximum power density of 24.9 µW/cm2 in a neutral 10 mM CSF and 8 mM glucose solution at 80 °C with an oxygen purge flow.

A rewritable electrochromic device (rECD) was developed to achieve handwriting function. The device was composed of four main components: a flexible conductive substrate, ruthenium-based metallo-supramolecular polymer (polyRu) as an electrochromic layer, electrolyte film, and a stainless steel stylus for writing. To avoid color diffusion between electrochromic pixels, a device structure with separate electrolyte pixels was designed. Next, to achieve handwriting feature without damaging the device, poly (vinylidene fluoride) was mixed with nanocellulose crystals to provide an anti-scratch electrolyte layer. The assembled device was switched between red and transparent states by applying an electrical potential of −0.7 V and +1.0 V, respectively. The rECD exhibited a high coloration efficiency of 332 cm2/C at 525 nm, rapid response times within a second. Moreover, the transmittance change without significant loss after 1000 color/bleach cycles was observed. The flexible rECD can be operated under bending condition without losing coloring ability. We demonstrated a feasible structure of rECD with durable electrolyte pixels for the first time. This strategy can be extended to the other practical handwriting applications.