光電所所訊

IGZO Thin Film Transistor Biosensors Functionalized with ZnO Nanorods and Antibodies

Professor Jian-Jang Huang's laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所黃建璋教授

We demonstrate a biosensor structure consisting of an IGZO (Indium-Gallium-Zinc-Oxide) TFT (thin film transistor) and an extended sensing pad. The TFT acts as the sensing and readout device, while the sensing pad ensures the isolation of biological solution from the transistor channel layer, and meanwhile increases the sensing area. The biosensor is functionalized by first applying ZnO nanorods to increase the surface area for attracting electrical charges of EGFR (epidermal growth factor receptor) antibodies. The device is able to selectively detect 36.2 fM of EGFR in the total protein solution of 0.1 ng/ml extracted from squamous cell carcinoma (SCC). Furthermore, the conjugation duration of the functionalized device with EGFR can be limited to 3 minutes, implying that the biosensor has the advantage for real-time detection.

Figure 1 Experimental flow of the biosensing. The protein solution of EGFR antibody was first extracted from SCCs. Bio-Rad protein assay was used to determine total protein concentration. The 100g/ml SCC protein solution was decimally diluted to 10 g/ml, 1g/ml, 100 ng/ml … 0.1 ng/ml. The electrical responses after applying the total protein solution were then extracted from the functionalized TFT sensor.

Figure 2 Electrical properties of the biosensor. The corresponding drain currents and current increments at various total protein concentrations are demonstrated.

All-optical switching in GaAs microdisk resonators by a femtosecond pump-probe technique through tapered-fiber coupling

Professor Ming-Hua Mao's laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所毛明華教授

We demonstrate ultrafast all-optical switching in GaAs microdisk resonators using a femtosecond pump–probe technique through tapered-fiber coupling. The temporal tuning of the resonant modes resulted from the refractive index change due to photoexcited carrier density variation inside the GaAs microdisk resonator. Transmission through the GaAs microdisk resonator can be modulated by more than 10 dB with a switching time window of 8 ps in the switch-off operation using pumping pulses with energies as low as 17.5 pJ. The carrier lifetime was fitted to be 42 ps, much shorter than that of the bulk GaAs, typically of the order of nanoseconds. The above observation indicates that the surface recombination plays an important role in increasing the switching speed. This work has been published in Optics Letters, Vol. 39, No. 17, pp. 4998, (2014).

Fig. 1. Scanning electron microscope image of the fully processed microdisk cavity with a diameter of 10 μm.

Fig. 2. Switch-off dynamics with modulation depth more than 10 dB.