## 1 Introduction  
Zeolites are crystalline microporous materials constructed of a network of silica and alumina tetrahedra. They are widely used in the chemical industry, in major petrochemical processes and, more recently, in biomass conversion [1]. Fluorescence microscopy is capable of monitoring chemical transformation of organic molecules at ambient temperature and pressure in liquid phase in zeolite crystals [2]. The aforementioned monitoring tool provides adequate measurements of catalytic activity for a rational and efficient catalyst design [3]. Due to the absence of control on the orientation of the particles, their monitoring method requires two crystals to assess the full three-dimensional catalytic activity. In this report, we propose an optofluidic system to manipulate the orientation of a ZSM-5 zeolite crystal along with medium control in order to use a single crystal for its complete assessment. The crystallization process and crystal morphology design is beyond the scope of this work. Optofluidics refers to the field of research involving the integration of microfluidics and optics in the same platform, where fluid and light are driven to interact [4]. Molecular fluorescence is an example of an optofluidic system [5]. Microfluidics technology,originally developed for ink jet printing [6], is a multidisciplinary research field that integrates technologies and principles from fluid dynamics, physics, biology, microtechnology, material science, and chemistry [7]. A manipulation method based on hydrodynamic forces developed in a microchannel for imaging cells in three-dimensions by cell rotation was proposed in [8]. The basis of their work is the fact that the parabolic velocity profile formed in a microfluidic channel at low Reynolds numbers (Re \(\ll\) 1) will expose two opposite sides of a cell near a wall to two different velocities, the one close to the wall slower, and the one close to the center faster. As a consequence, a torque will act on the cell and a rotation will be induced. By using computational fluid dynamics (CFD), an analysis of particle translation and rolling near surfaces was carried out by [9]. In their work, they use the three-dimensional numerical solution of the Navier-Stokes equations computed by CFD to estimate the hydrodynamic drag force and torque exerted on a microsphere which induces the translation and rotation of the body. A study of detachment and motion of a glass microsphere in a cylindrical PDMS microfluidic channel has been carried out [10]. They used a nonionic surfactant (Tween 80) to minimize the adhesion forces, because the particle motion was not possible without surfactant due to strong interactions between the channel and particle. Acoustic viscous torque has been used to trap and rotate spherical and elongated microparticles with an acoustic field of two orthogonal standing waves [11]. Their approach is used for rotation of suspended particles around a vertical axis at the pressure node. In this work, we describe an optofluidic system that uses two computer-controlled syringe pumps to manipulate heavy particles in one dimension near a quartz microchannel's bottom wall. A straight-channel geometry has been chosen for two reasons: (1) maintaining the manipulation capability through the full length of the channel and (2) keeping the crystal far from lateral walls where would get stuck. The two syringe pumps and the microfluidic channel design produced hydrodynamic forces that the authors used to translate and rotate ZSM-5 zeolite crystals. Fluid structure interaction (2D) simulations with COMSOL demonstrate that a zeolite-like item toward the bottom of the microchannel travels more quickly than the crystals shown on video. A negative volumetric force was utilized in the COMSOL simulation to reduce the velocity of the moving item in order to match the simulated and experimental velocities. Three-dimensional (3D) imaging at the micrometer scale is important for a variety of applications, including materials science, biology, and medicine.