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In Situ Regeneration of Si-based ARROW-B Surface Plasmon Resonance Biosensors.

Hsu HF, Lin YT, Huang YT, Lu MF, Chen CH - J Med Biol Eng (2015)

Bottom Line: SPR was used to monitor the regeneration processes.The experimental results show that the sensing response did not significantly change after the sensor was reused more than 10 times.In situ regenerations of the sensors were achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu, Taiwan.

ABSTRACT

Si-based antiresonant reflecting optical waveguide type B (ARROW-B) surface plasmon resonance (SPR) biosensors allow label-free high-sensitivity detection of biomolecular interactions in real time. The ARROW-B waveguide, which has a thick guiding layer, provides efficient coupling with a single-mode fiber. The Si-based ARROW-B SPR biosensors were fabricated by using the standard semiconductor fabrication processes with a single-step lithography. A fluid flow system was designed to transport samples or analytes. The waveguide consists of propagation and SPR sensing regions. The propagation regions in the front and rear of the SPR sensing region have a symmetric cladding structure to isolate them from environmental changes. A high-index O-ring is used to seal the liquid flow channel. The intensity interrogation method was used to characterize the sensors. The sensitivity of the biosensors was 3.0 × 10(3) µW/RIU (refractive index unit) with a resolution of 6.2 × 10(-5) RIU. An in situ regeneration process was designed to make the sensors reusable and eliminate re-alignment of the optical measurement system. The regeneration was realized using ammonia-hydrogen peroxide mixture solutions to remove molecules bound on the sensor surface, such as self-assembled 11-mercapto-1undecanoic acid and bovine serum albumin. SPR was used to monitor the regeneration processes. The experimental results show that the sensing response did not significantly change after the sensor was reused more than 10 times. In situ regenerations of the sensors were achieved.

No MeSH data available.


Surface morphology of gold film
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Fig4: Surface morphology of gold film

Mentions: Figure 4 shows the flow chart of the single-step lithography fabrication processes. In the beginning of chip fabrication, RCA cleaning is performed on 6″ (15.24 cm) silicon wafers to remove organic, native chemical oxide, and ionic contaminants from the wafer surface. Plasma-enhanced chemical vapor deposition (PECVD) was used to deposit a 2-μm-thick SiOx layer as the lower second cladding layer. The thickness was measured using an n&k analyzer and verified as 2 μm. The refractive index of the film was measured as 1.463 (due to the structure of SiOx instead of pure SiO2). Then, a spin-coater was used to spin hydrogen silsesquioxane (HSQ) onto the wafer at 3000 rpm for 30 s. The thickness and refractive index were 0.31 μm and 1.400, respectively, just after spinning. After curing at 350 °C for 15 min, a film with a thickness of 0.28 μm and a refractive index of 1.380 was obtained. PECVD was also used to deposit a 4-μm-thick core layer. Then, repeating the previous step, HSQ was spin-coated to form the upper first-cladding layer for the propagation region and the buffer layer for the sensing region. The lithography process was then used to define waveguide channels. First, Al with a thickness of 3000 Å was deposited via e-gun evaporation as the hard mask. This wafer was put into a track system and an I-line stepper for photoresist coating, exposure, and development. Subsequently, 3000-Å-thick Al and the 6.68-μm-thick SiOx/HSQ layers were etched using an inductively coupled plasma dry etcher. Then, residual photoresist and Al were removed using 120 °C H2SO4/H2O2 for 10 min using a wet bench. A shadow mask was used to define the sensing region and the propagation regions. After aligning the sensing region of mask 2 to the middle of the channels and using polyimide film tape to fix it, the sensing regions were sheltered, and the uncover regions were the front and rear propagation regions. The upper second cladding layer SiOx on the front and rear propagation regions was deposited on the aforementioned wafer by PECVD. The deposited thickness was 1.80 μm. Subsequently, mask 2 was removed, and a 0.12-μm-thick Si3N4 layer was deposited using PECVD. An e-gun was used to deposit Cr and Au films with thicknesses of 3 and 15 nm, respectively. Figure 5 shows an AFM image of the fabricated biosensor, which shows that the evaporated gold film was a continuous film with a roughness of 1.165 nm.Fig. 4


In Situ Regeneration of Si-based ARROW-B Surface Plasmon Resonance Biosensors.

Hsu HF, Lin YT, Huang YT, Lu MF, Chen CH - J Med Biol Eng (2015)

Surface morphology of gold film
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4491115&req=5

Fig4: Surface morphology of gold film
Mentions: Figure 4 shows the flow chart of the single-step lithography fabrication processes. In the beginning of chip fabrication, RCA cleaning is performed on 6″ (15.24 cm) silicon wafers to remove organic, native chemical oxide, and ionic contaminants from the wafer surface. Plasma-enhanced chemical vapor deposition (PECVD) was used to deposit a 2-μm-thick SiOx layer as the lower second cladding layer. The thickness was measured using an n&k analyzer and verified as 2 μm. The refractive index of the film was measured as 1.463 (due to the structure of SiOx instead of pure SiO2). Then, a spin-coater was used to spin hydrogen silsesquioxane (HSQ) onto the wafer at 3000 rpm for 30 s. The thickness and refractive index were 0.31 μm and 1.400, respectively, just after spinning. After curing at 350 °C for 15 min, a film with a thickness of 0.28 μm and a refractive index of 1.380 was obtained. PECVD was also used to deposit a 4-μm-thick core layer. Then, repeating the previous step, HSQ was spin-coated to form the upper first-cladding layer for the propagation region and the buffer layer for the sensing region. The lithography process was then used to define waveguide channels. First, Al with a thickness of 3000 Å was deposited via e-gun evaporation as the hard mask. This wafer was put into a track system and an I-line stepper for photoresist coating, exposure, and development. Subsequently, 3000-Å-thick Al and the 6.68-μm-thick SiOx/HSQ layers were etched using an inductively coupled plasma dry etcher. Then, residual photoresist and Al were removed using 120 °C H2SO4/H2O2 for 10 min using a wet bench. A shadow mask was used to define the sensing region and the propagation regions. After aligning the sensing region of mask 2 to the middle of the channels and using polyimide film tape to fix it, the sensing regions were sheltered, and the uncover regions were the front and rear propagation regions. The upper second cladding layer SiOx on the front and rear propagation regions was deposited on the aforementioned wafer by PECVD. The deposited thickness was 1.80 μm. Subsequently, mask 2 was removed, and a 0.12-μm-thick Si3N4 layer was deposited using PECVD. An e-gun was used to deposit Cr and Au films with thicknesses of 3 and 15 nm, respectively. Figure 5 shows an AFM image of the fabricated biosensor, which shows that the evaporated gold film was a continuous film with a roughness of 1.165 nm.Fig. 4

Bottom Line: SPR was used to monitor the regeneration processes.The experimental results show that the sensing response did not significantly change after the sensor was reused more than 10 times.In situ regenerations of the sensors were achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu, Taiwan.

ABSTRACT

Si-based antiresonant reflecting optical waveguide type B (ARROW-B) surface plasmon resonance (SPR) biosensors allow label-free high-sensitivity detection of biomolecular interactions in real time. The ARROW-B waveguide, which has a thick guiding layer, provides efficient coupling with a single-mode fiber. The Si-based ARROW-B SPR biosensors were fabricated by using the standard semiconductor fabrication processes with a single-step lithography. A fluid flow system was designed to transport samples or analytes. The waveguide consists of propagation and SPR sensing regions. The propagation regions in the front and rear of the SPR sensing region have a symmetric cladding structure to isolate them from environmental changes. A high-index O-ring is used to seal the liquid flow channel. The intensity interrogation method was used to characterize the sensors. The sensitivity of the biosensors was 3.0 × 10(3) µW/RIU (refractive index unit) with a resolution of 6.2 × 10(-5) RIU. An in situ regeneration process was designed to make the sensors reusable and eliminate re-alignment of the optical measurement system. The regeneration was realized using ammonia-hydrogen peroxide mixture solutions to remove molecules bound on the sensor surface, such as self-assembled 11-mercapto-1undecanoic acid and bovine serum albumin. SPR was used to monitor the regeneration processes. The experimental results show that the sensing response did not significantly change after the sensor was reused more than 10 times. In situ regenerations of the sensors were achieved.

No MeSH data available.