Graphene "wrinkles": elastic graphene photo-detectors that can be implanted in the body

Graphene, a red-hot two-dimensional material, is actually a single-layer carbon atom hexagonal lattice with broadband absorption, high carrier mobility, and plasticity. It is widely used in photo-detector research. However, due to its low absorption rate in the visible and near-infrared regions, it has hindered the development of graphene broadband photo-detectors. Therefore, the current research on graphene photo-detectors is mostly focused on hybrid systems that enhance light absorption. However, such a hybrid system is complex to combine, reducing the carrier mobility due to heterogeneous interfaces, or narrowing the detection bandwidth due to dependence on plasma or optical resonance, resulting in limited application scope and increased manufacturing costs.

In the recent "AdvancedMaterials", Professor SungWooNam of the University of Illinois at Urbana-Champaign reported a new strain-tuned elastic graphene photo-detector, and the problem-solving strategy is subtle. The detector is based on pleated three-dimensional graphene, a "wrinkle" material that enhances light signals and combines with colloidal photonic crystals (CPC) with both wavelength-tuned wavelength selectivity. This curved three-dimensional structure greatly increases the areal density of the graphene, achieving an extinction of more than one order of magnitude (12.5 times) and an increase in photoelectric response of 400%. Furthermore, by applying a strain of 200% to the material, a light response modulation of about 100% is obtained. Thus, a strain-tuned optical filter and an elastic graphene photo-detector are obtained.(CrumpledGraphenePhotodetectorwithEnhanced,Strain-Tunable,andWavelength-SelectivePhotoresponsivity.Adv.Mater.,2016,DOI:10.1002/adma.201600482)

The researchers applied pre-strain to the acrylic matrix at the bottom of the graphene during synthesis to obtain a three-dimensional graphene fold structure under strain release, and its extinction was 12.5 and 6.6 times that of the flat graphene, respectively. This method is also suitable for other emerging two-dimensional materials such as Molybdenum disulfide(MoS2). On this basis, the researchers built a high-performance photoelectric detection device by combining a corrugated graphene channel that produces photocurrent and a corrugated gold contact that collects photoelectric signals. Photocurrent is measured at the connection of two parts by laser irradiation. Under different uniaxial tensile strains (0%-200%), the laser opening and closing time is controlled, and the dynamic photo-response data of elastic photo-detector with fast response speed, good reproducibility, and response enhancement of 370 % is obtained.

Subsequently, the researchers replaced the detector substrate with a highly biocompatible, highly flexible Silicon polymer and applied 11.1 % of the tensile bending strain to the human brain model and the heart model. The results show that the current and voltage(V) curves on the surface and surface are similar and stable in thousands of tensile cycles. This means that this photoelectric detection system has a very high application potential in the field of implant Biomedicine and Optoelectronics.

Finally, colloidal photonic crystals are embedded in flexible matrices and used as strain tuning optical filters. The UV-visible spectrum shows that when the strain is from 0 % to 30 %, the reflected peak is blue-shifted, and the color changes between orange and green, making the integrated CPC-elastic graphene photo-detector unique to the binding wavelength selectivity and enhancement photoelectric response. potential.

In 2015, the Zhangguangyu research team of the Institute of Physics of the Chinese Academy of Sciences also reported on a tactile sensor based on flexible graphene materials(ACSNano, 2015, 9,1622-1629, DOI: 10.1021 / nn506341 U). The "electronic skin" has high transparency, sensitivity, response time of one-tenth of the skin, and can withstand tens of thousands of stress tests.

It is believed that in the continuous in-depth research, graphene flexible detector will play a higher practical value in military and medical health.

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