Hybrid nanophotonic–microfluidic sensor for highly sensitive liquid and gas analyses

Abstract

Today, a lab-on-a-chip is one of the most promising ways to create sensor devices for gas and liquid analysis for environmental monitoring, early diagnosis, and treatment effectiveness assessment. On the one hand, this requires a large number of measurements and, on the other hand, involves minimum consumption of the test analytes. Combination of highly sensitive photonic integrated circuits (PICs) with microfluidic channels (MFCs) is necessary to solve this problem. In this work, PICs based on a silicon nitride platform integrated with MFCs for studying liquids and gases were developed. Different concentrations of isopropanol in de-ionized water were used as the analyte. Based on this, the sensitivity (S) and detection limit (DL) of the analyzed solution were evaluated. Entire system calibration was carried out to calculate S and DL, considering experimental and numerical simulation data. This development may be of interest as a promising platform for environmental monitoring and realization of point-of-care strategy for biomedical applications.

In Situ Monitoring of Layer-by-Layer Assembly Surface Modification of Nanophotonic-Microfluidic Sensor

“…Among them MZIs and MRRs are the most common sensors for biosensing applications due to the plain fabrication process and well-explored data processing algorithms . Also, the combination of PICs (MZIs and MRRs) with MFCs for comparison of their detection limit (DL) and sensitivity (S) on a Si 3 N 4 platform with fixed microfludic parameters has been already presented for liquid and gas samples . The main advantages are the high S and ultralow DL, ultralow necessary volume for one PIC, and possibility for determining the concentrations of unknown two-component solutions or gas mixtures.…”

“…Chip topology included a Si wafer layer with a thickness of about 540 μm, then a silicon oxide layer as a buffer formed on it (SiO 2 ) with a thickness of 2.6 μm, and an optical layer of Si 3 N 4 formed on top by low-pressure chemical vapor deposition (LPCVD) with a thickness of 450 nm. The PICs fabrication process was previously reported …”

“…For the study of the LBL assembly, first, BSA with a concentration 2 mg/mL in DI water was pumped through the PICs array for 15 min with the liquid volume transported per time set to 20 μL/min [Figure a]. The PICs array consisted of 4 MZIs (see Figure S1 in Supplement 1) with varying distances between the interferometer branches Δ L (952 μm, 892 μm, 712 μm, 652 μm) and 6 MRR gaps between the bus and loop waveguide (600–1100 nm, step 100 nm) . Since the dip wavelength shift (Δλ c ) was monitored for fixed microfluidic channel width L Ch = 100 μm for all PICs arrays described above, the geometrical difference did not effect the final shift.…”

“…For DI water and PDMS in the strict channel interference order, m was 1055 for wavelength 1550.13 nm. Afterward, Δλ c = 53.66 nm from λ c for reference DI water and BSA film in the MFC [Figure e] was calculated based on variation n eff ( BSA ) by using eq : Having obtained n eff ( BSA ) and knowing the complete geometry of the waveguide with the BSA layer thickness, the next step was to simulate the real refractive index. According to the simulation results, the refractive index turned out to be equal to 1.358 ± 0.007 (see Figure S3 in Supplement 1), which is close to presented data in literature …”

“…13 Also, the combination of PICs (MZIs and MRRs) with MFCs for comparison of their detection limit (DL) and sensitivity (S) on a Si 3 N 4 platform with fixed microfludic parameters has been already presented for liquid and gas samples. 18 The main advantages are the high S and ultralow DL, ultralow necessary volume for one PIC, and possibility for determining the concentrations of unknown two-component solutions or gas mixtures. However, there are no studies that used MZIs and MRRs for monitoring LBL assembly and controlling surface functionalization and immobilization at fixed microfluidic and setup parameters simultaneously in real time.…”