Atomic layer deposition (ALD) of 2D MoS2 for soft gripper application

• Main Author: Gihm, Wenqi
• Other Authors: Lee Pooi See
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Materials; Thin film
• Online Access: https://hdl.handle.net/10356/176397
• Institution: Nanyang Technological University

Soft robotics are on a rise as a promising sector due to their applications in various industries especially in manufacturing and service, and agri-food related. The smart grippers are capable at grabbing delicate objects (e.g. fruits, vegetables, raw egg) carefully without any damages. Piezoelectric materials are the foundation in creating these robotic grippers due to their unique property which produces electricity when mechanically deformed. Among the different piezoelectric materials, molybdenum disulfide (MoS2) is used because of its flexibility, decent piezoelectric properties, and adjustable bandgap. To form MoS2 films with high quality, advanced thin film deposition technique is necessary. Atomic layer deposition (ALD) is a process strong enough to fabricate films with thicknesses as low as a nanometre. Moreover, it operates in a self-limiting manner, follows a cyclic growth process, and has the capability to deposit thin films at relatively low temperatures. Additionally, the integration of 3D structures such as inverse opal helps enhance piezoelectric properties of MoS2. To fabricate homogenous inverse opal structures, spin coating emerges as a rapid and feasible method. In this study, spin coating was utilised to fabricate 2D hollow MoS2 shells through a layer of polystyrene beads of varying sizes. This was followed by depositing MoS2 atop the polystyrene beads by using ALD which can exhibit decent piezoelectric properties. Evaluation of surface morphology results revealed distinct outcomes based on different spin coating parameters including spin speed, number of spin coating steps, addition of surfactants and deposited volume of polystyrene solution. After comparison, a one-step spin coating process with the inclusion of the surfactant, BYK-333, in the coating solution, deposited with volumes of 100 µL and 80 µL, yielded the best results for the 500 nm and 1 µm polystyrene beads respectively.