Soil is a highly scattering media that inhibits imaging of plant-microbial-mineral interactions that are essential to plant health and soil carbon sequestration. However, wavefront shaping can be used to focus light through or even deep inside highly scattering objects. In this work, we seek to overcome the fundamental challenges of imaging through soil minerals by developing a custom wavefront shaping method for a multiphoton microscope. We use the adaptive stochastic parallel gradient descent optimization algorithm combined with Hadamard basis to correct the aberration and the scattering in order to focus through the soil.
Soil is a highly scattering media that inhibits imaging of plant-microbial-mineral interactions that are essential to plant health and soil carbon sequestration. In this work, we seek to overcome the fundamental challenges of imaging through soil minerals by developing a custom wavefront sensor-less adaptive optics (AO) system for a multiphoton microscope. We are using a combined experimental and modeling approach, characterizing mineral optical characteristics with scatterometry, modeling the wavefront distortion and the image quality degradation after imaging through the soil medium, simulating the image quality improvement with AO correction, and experimentally testing our models with a stand-alone AO testbed.
In this work, we report a new SPR sensor configuration which enables a single-point detection strategy for 2D angular interrogated SPR sensor array. The single-point detection strategy for 2D SPR measurements is enabled by the cooperation of two digital micro-mirror devices (DMDs). Specifically, one DMD is used to conduct spatial scanning along the vertical direction of the sensor chip; and the other DMD is used to conduct spatial scanning along the horizontal direction. Thanks to the programmability of DMDs, arbitrary and instant access of interrogation angle and sensing site are achieved with no limitation in integration time. Besides, no mechanical scanning is required in the entire system. This configuration suffices a single-point detector for 2D angular interrogated SPR measurements that can be readily optimized for nearly ideal performance, increased sensing capacity without sacrificing the sensitivity.
In this work, we present a digital micro-mirror device (DMD)-enabled real-time biosensing array based on angular interrogation surface plasmon resonance (SPR) with a single point photodetector. It has been studied that the performance of SPR sensors are predominantly limited by photon statistics, which can be achieved by increasing the photon capture efficiency and dynamic range of the detector. Such attributes uniquely put the single point photodetector as a potential light detecting element in high performance SPR sensors. In our DMD-based-SPR system, angular scanning is achieved by the DMD which facilitates SPR measurements with a single point photodetector, leading to a high-performance system with user-selectable interrogation range, enhanced S/N ratio and fast data throughput. Experimental results demonstrate a system resolution of 3.54×10−6 in terms of refractive index unit (RIU). Using a 4-channel array setup, we have performed real-time monitoring of bovine serum albumin (BSA)/anti-BSA binding interactions at various concentration levels. The limit of detection (LOD) is 27 ng/mL. DMD-based SPR interrogation opens up a new design route for practical solid-state SPR biosensors.
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