Phuc Hong Pham

Straight movement of micro containers based on ratchet mechanisms and electrostatic comb-drive actuators

This paper describes the design, simulation and fabrication of a micro conveyer system (MCS) with straight displacement of micro containers based on ratchet mechanisms and electrostatic comb-drive actuators. This MCS consists of linear comb actuators, micro containers and ratchet racks. The micro containers can be moved with different velocities by comb-drive actuators through ratchet teeth. In this study, a SOI wafer with a device layer of 30 ?m and a buried SiO2 layer of 4 ?m is used. Each module of the MCS has dimensions of 6 ? 6 mm2, is fabricated by using only one mask, ICP-RIE and vapor HF etching techniques, and can be assembled to create more complex conveyance systems for different applications, such as in bio-chemical analysis or a micro total analysis system (?-TAS) to transport and classify small samples. In our experiments, the movement of the micro container has been tested with a driving frequency ranging from 5 Hz to 40 Hz. The velocity of the container was proportional to the frequency and matched very well with theoretical calculation.

A micro transportation system (MTS) with large movement of containers driven by electrostatic comb-drive actuators

This paper describes a Si micro transportation system (MTS) to drive micro containers in straight movement based on a ratchet mechanism and electrostatic comb-drive actuators. This MTS consists of linear comb actuators, micro containers and ratchet racks. The lateral movements of ratchet racks push the micro containers which move straight in a perpendicular direction with different velocities. The MTS was fabricated from a SOI wafer by using only one mask. In our experiments, the movement of the micro container has been tested with driving frequency ranges from 1 Hz to 20 Hz. The velocity of the micro container was proportional to the driving frequency, and it matched well with the theoretical calculation.

Study of valveless electromagnetic micropump by volume-of-fluid and OpenFOAM

The paper reports the first study on the backpressure of a valveless electromagnetic micropump using the volume-of-fluid (VOF) technique and open-source code OpenFOAM. The micropump consists of a vibrating diaphragm and fluidic microchannel connected to inlet and outlet tubes. The imbalance in fluid resistance of the fluidic microchannel during a vibration cycle of the diaphragm creates backpressure in the pump, which in turn produces a difference in water level between the inlet and outlet tubes. In this study, VOF was used in a transient simulation to obtain this difference in water level and then the backpressure. The obtained backpressure showed a slight discrepancy with the experimental data. The discrepancy was probably due to the difference in the wall surface quality of the fluidic microchannel between the simulation model and experimental device. These results are useful for analytical and numerical research on these types of micropumps and can easily be applied in an open-source code simulator with almost zero cost.

Multimodule Micro Transportation System Based on Electrostatic Comb-Drive Actuator and Ratchet Mechanism

We present a novel multimodule micro transportation system (MTS), which can drive micro containers in straight, curved, and T-junction paths based on electrostatic comb-drive actuator and ratchet mechanism. The transported objects are micro containers, which have two pairs of driving wings and anti-reverse wings attached to a body. Their movement is like a water strider, i.e., its driving wings rotate backward to generate reaction force to push the containers forward, while the anti-reverse wings act as a ratchet mechanism to prevent the container from moving backward. By developing three basic modules, i.e., straight, turning, and T-junction modules, the different configurations of the MTS can be built from these modules conveniently. Each module consists of ratchet racks driven by electrostatic comb-drive actuators. Containers having length, width, and thickness of 500, 250, and 30 μm, respectively, were driven to move with a changeable velocity up to 1000 μm/sec in straight, turning, and T-junction modules. The velocity of the container was proportional to the frequency of driving voltage. By utilizing silicon micromachining technology, a prototype of MTS was fabricated from silicon-on-insulator wafer with only one mask.

Single mask, simple structure micro rotational motor driven by electrostatic comb-drive actuators

We report a design and fabrication of a new micro rotational motor (MRM) using silicon micromachining technology with the overall diameter of 2.4 mm. This motor utilizes four silicon electrostatic comb-drive actuators to drive the outer ring (or rotor) through ratchet teeth. The novel design of the anti-reverse structure helps us to overcome the gap problem after deep reactive ion etching of silicon. The MRM was fabricated by using silicon on insulator wafer with the thickness of the device layer being 30 µm and one mask only. The motor was successfully tested for performance. It was driven by periodic voltage with different frequencies ranging from 1 to 50 Hz. The angular velocity of the outer ratchet ring was proportional to the frequency. Moreover, when the driving frequency is lower than 30 Hz, the experiment results perfectly match the theoretical calculation.

Tangential and perpendicular driving micro transmission systems based on ratchet mechanism and electrostatic actuator

This paper presents comprehensive improvements of micro motion transmission systems (MTS), which driven by electrostatic comb-drive actuators through ratchet mechanism to move micro objects unidirectionally in straight, curved and rotational paths. The first MTS is the tangential driving MTS, in which the driven objects are moved by tangential force. A rotational gearing MTS and micro conveyance system (MCS) based on this driving mode will be presented. Thanks to the new designs of directional guider of the micro containers and new turning module, the containers can move in both straight and curved paths in the tangential MCS. The second MTS is the perpendicular driving MCS, which drives micro containers by the perpendicular driving force, i.e. the moving direction of the container is perpendicular to the actuation direction. Movement velocities of the containers can be controlled by changing the driving frequency.

Micro Ratcheting Transmission Systems Based on Electrostatic Actuator

This paper presents design and fabrication of a silicon micro ratcheting transmission system (RTS) that utilizes electrostatic comb-drive actuators to rotate a gear ring (or rotor) through a ratchet mechanism. The rotational actuator is engaged with the gear ring through ratchet teeth at one end, and reciprocally rotates around an elastic point at the other end based on electrostatic force. Rotational motion and torque from driving gear ring are transmitted smoothly to driven gears through involute profile gear teeth. Novelty design of anti-gap structures have overcome the unavoidable gap problem occurred in deep reactive ion etching of silicon. The micro RTS has been fabricated and tested successfully. The rotation of the motor is linearly proportional to driving frequency up to 40 Hz.

Novelmicro Transportation Systems Based on Ratchetmechanism and Electrostatic Actuators

This paper describes a design and fabrication of Si micro transportation systems (MTS) to drive microcars based on ratchet mechanism and electrostatic comb-drive actuators. This MTS consists of linear and rotational comb actuators, microcars, and micro ratchet mechanism. The microcars can be moved with different velocities by comb-drive actuators through ratchet teeth. In this study, the MTS was fabricated by using SOI wafer with device layer of 30 mum, buried SiO2 layer of 4 mum, and with only one mask. In our experiments, the movement of the microcar has been tested with driving frequency ranges from 5 Hz to 40 Hz. The velocity of the microcar was proportional to the driving frequency, and it matched well with theoretical calculation.

Study on Fabrication of Polymer Electrostatic Comb-drive Actuator by DXRL Technique

This paper reports a novel approach to fabricate poly-methyl-meth-acrylate (PMMA) electrostatic comb-drive actuator using the deep X-ray lithography (DXRL) technique. The designed actuator consists of 140 units of interdigitated parallel capacitors with the finger gap and width being 2mum and 4mum respectively, and the thickness of the structure is 200 mum, which makes the aspect ratio 50:1. A brief description of the design and simulation with ANSYS are also presented in this paper

A Si micro conveyer system based on electrostatic comb-drive actuators

We report a design and fabrication of micro conveyer system (MCS) based on electrostatic comb-drive actuators using SOI wafer. This MCS consists of linear comb actuator, rotational comb actuator, micro containers, and ratchet mechanism. Micro containers, used for carrying micro and nano samples such as protein, cells, are moved by comb-actuators through ratchet teeth. Each MCS, which has dimension of 1 times 1 cm2, is fabricated by using ICP-RIE and vapor HF etching techniques. The fabricated comb actuators were tested for electrostatic effect. Experiment results were very close to the simulation results