Invited: Metal-Semiconductor-Metal Photocurrent Chip for Hydrogen Peroxide and Biomolecular Sensing with Chemiluminescence
Authors: Ko Fu-Hsiang , Lin Ching-Chang , Sun Da-Shiuan , Pan Tung-Ming 
Published: February 2020

Photodetectors are generally the most promising, representative and widely-used type of detectors, and the applications of photodetectors are quite extensively[1-3]. Basically photodetectors are made of photosensitive elements which are able to turn the light signal into electrical signal. Nowadays, the detecting wavelength region is very broad and can be classified into infrared, visible light and ultraviolet zone; furthermore, the applications of each region are manifold especially in visible light region. Additionally owing to the nature of fast responding speed, it promises photodetectors an advantageous future in biomedical sensing territory[4-5]. This study is focus on fabrication method of the flexible[6-8] photodetectors and application to biomolecule sensing through luminescence. The photosensitive element is based on single crystalline silicon semiconductor material which is treated with chemical etching process to achieve pliable characteristic[9]. Then, the metal-semiconductor-metal[10-14]structural flexible photodetectors are achieved after integrated with simple fabricating processes. In detail, the accomplished devices are handled with immobilization steps to fix the target enzyme which is able to catalyze the luminescent reaction (Fig.1). Owing to only extremely stable sensor for biomedical use, it is necessary to ensure the operation function at any crucial conditions. In this study, we provide a portable biomolecule sensor with outstanding flexible characteristic and high sensitivity and it exhibits illustrious stable consequence in various situations.

Figure 1.Schematic diagram of immobilization process flow and luminescence detection.
A pliable silicon chip measured under fifty micrometers in thickness is achieved through a simple method via alkaline etchant. The silicon chip with designed thickness is featured of great flexibility and relatively little fragility. A surface modification is applied to the flexible silicon chip with non-toxic and easy-arranged texturing solution from texturization process. Owing to anisotropic etching, the three-dimensional structure of pyramidal shape is constructed onto the chip surface. The reflectivity decreases advantageously in virtue of increasing roughness, and the final reflectivity is only one-fourth in comparison with original smooth chip surface due to formation of surface microstructure. The flexible MSM photodetectors are accomplished after mantling metal electrode with well-designed pattern. The semiconductor material we used is featured of high natural abundance and the manufacturing processes are considerably uncomplicated.
In taking advantage of immobilization technique, the targeting enzyme is bound to photodetector devices and as-prepared devices are employed in optical sensing of luminescence which is catalyzed by the immobilized enzyme. This optical sensor exhibits great flexibility and remarkable durability and shows marvelous stability even in various stretching conditions. Furthermore, the photodetector devices are featured portable and cost-efficient. A novel application of this detector in healthcare field which is a significant issue nowadays is performed on available hair dye products. The examination is taken into consideration owing to the potential damage caused by hydrogen peroxide of which the main ingredient in hair dye products (Fig.2). For this interdisciplinary-technology-based device, the flexible optical sensor can be utilized in multiple regions and it can be integrated with promising instruments in virtue of great mechanical property.

Figure 2.Hydrogen peroxide detections for hair dye samples through luminescence sensing by flexible MSM photodetectors.

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