Microfluidic Waveguide Sensor Based On Local Surface Plasmon Effect Of Gold Nanoparticles

Sensors are the main way and means for humans to obtain information in the fields of production and scientific research.Whether it is the study of macrocosm or the observation of microscopic cells,almost all modernization studies are inseparable from a wide range of sensors.At present,the sensors based on the LSPR effect of gold nanoparticles are mostly based on optical fibers or film.Fiber optic sensors have the advantage of being less susceptible to electromagnetic interference and higher sensitivity,but are limited in applications in planar photonics integration.Thin film type sensor is simple to prepare but has low sensitivity.Therefore,a planar waveguide sensor based on LSPR effect of gold nanoparticles is proposed in this paper.The research of waveguide sensors,especially the polymer waveguide sensors,is relatively rare.It can combine the advantages of fiber-optic sensors and film type sensor.Since the core layer and the cladding refractive index of the polymer material are easily adjusted,the structural design of the waveguide device is relatively flexible.In addition,it can be easily integrated with various microfluidic channels to construct an automated,intelligent microfluidic chip.Therefore,it has broad market prospects in biochemical detection,environmental monitoring and other fields.In this paper,a polymer microfluidic waveguide sensor based on the LSPR effect of gold nanoparticles was studied.The sensor was analyzed and studied from three aspects:material synthesis,device fabrication and performance testing.The main work is as follows:1.A gold nanoparticle colloidal solution with good dispersibility and uniformity was prepared by sodium citrate reduction of chloroauric acid.After being bound to the polymer SU-8 film,UV-visible absorption experiments were carried out.The results showed that the peak of the absorption increased linearly with the increasing of the refractive index of the NaCl solution.The sensitivity of intensity change was 0.1778△A/RIU and the linearity was 0.9026.The polymer SU-8 waveguide was prepared by photolithography process,and the gold nanoparticles were bound after the modification of the waveguide surface.Then,the different concentrations of NaCI solution were detected,and the sensitivity of the intensity change was 1.8608 DA/RIU,which was about 10 times higher than that of polymer SU-8 film,and the linearity was also increased from 0.9026 to 0.9608.2.A microfluidic channel substrate based on polymer PDMS was prepared and the effects of various size parameters on the gas tightness of PDMS microfluidic channels were investigated.The results showed that PDMS substrates with thickness ranging from 0.3 mm to 0.5 mm and narrow width on both sides of the hole might have good air tightness.After integration with the polymer SU-8 waveguide,the microfluidic sensor was used to measure the same NaCl solution as above.The results showed that the sensitivity was 3.9833 △A/RIU,which was about 2 times higher than that of without microfluidic channel,20 times more than that of polymer SU-8 film,and the linearity was further improved to 0.9820.Which proved that the presence of microfluidic channel could improve the stability and sensitivity of the sensor system.3.After determining the optimum reaction time,Alpha fetoprotein(AFP)solution was detected by polymer film sensor and microfluidic waveguide sensor.The results showed the detection limit of AFP antigen was 1 ng/ml,the detection range was 1 ng/ml-400 ng/ml,and the absorption peak intensity of the film method varies linearly with the logarithm of the concentration with a linearity of 0.9635,while the absorption peak of microfluidic method showed a linear change with the concentration with a linearity of 0.9762.In order to study its selection specificity,IgG、Anti-IgG、Whey Protein and BSA solutions with concentration of 4 μg/ml were injected into the microfluidic sensor,respectively.The results showed that the sensor had a good selectivity.Finally,the microfluidic sensor was used to measure some known concentrations of AFP solution and compared them to real values.The results showed the minimum error of the detected concentration is 5.6%.