Xavier Arouette

Characterization of a bonding-in-liquid technique for liquid encapsulation into MEMS devices

We demonstrate and characterize a new bonding-in-liquid technique (BiLT) for the encapsulation of liquids in MEMS devices. Liquid encapsulation enables innovative MEMS devices with various functions exploiting the unique characteristics of liquids, such as high deformation and spherical shape due to surface tension. Interfusion of air bubbles, variation of the liquid quantity and leakage of the encapsulated liquid must be avoided, or device performance will deteriorate. In BiLT, two structural layers are passively aligned and brought into contact in a solution, and the encapsulation cavities are filled uniformly with liquid, without air bubbles. A UV-curable resin is used as an adhesive that does not require heat or vacuum to bond the layers, but UV irradiation. DI water, glycerin and phosphate buffer saline were successfully encapsulated in silicon structural layers with PDMS membranes. We experimentally evaluated the bond strengths and alignment accuracy of BiLT in order to provide crucial information for the application of this process to the packaging and/or manufacturing of MEMS devices. Since conventional aligners are not applicable to BiLT, we experimentally evaluated the accuracy of an in-solution passive alignment process, which made use of matching concave and convex structures.

Dynamic Characteristics of a Hydraulic Amplification Mechanism for Large Displacement Actuators Systems

We have developed a hydraulic displacement amplification mechanism (HDAM) and studied its dynamic response when combined with a piezoelectric actuator. The HDAM consists of an incompressible fluid sealed in a microcavity by two largely deformable polydimethylsiloxane (PDMS) membranes. The geometry with input and output surfaces having different cross-sectional areas creates amplification. By combining the HDAM with micro-actuators, we can amplify the input displacement generated by the actuators, which is useful for applications requiring large deformation, such as tactile displays. We achieved a mechanism offering up to 18-fold displacement amplification for static actuation and 12-fold for 55 Hz dynamic actuation.

Demonstration of Vibrational Braille Code Display Using Large Displacement Micro-Electro-Mechanical Systems Actuators

In this paper, we present a vibrational Braille code display with large-displacement micro-electro-mechanical systems (MEMS) actuator arrays. Tactile receptors are more sensitive to vibrational stimuli than to static ones. Therefore, when each cell of the Braille code vibrates at optimal frequencies, subjects can recognize the codes more efficiently. We fabricated a vibrational Braille code display that used actuators consisting of piezoelectric actuators and a hydraulic displacement amplification mechanism (HDAM) as cells. The HDAM that encapsulated incompressible liquids in microchambers with two flexible polymer membranes could amplify the displacement of the MEMS actuator. We investigated the voltage required for subjects to recognize Braille codes when each cell, i.e., the large-displacement MEMS actuator, vibrated at various frequencies. Lower voltages were required at vibration frequencies higher than 50 Hz than at vibration frequencies lower than 50 Hz, which verified that the proposed vibrational Braille code display is efficient by successfully exploiting the characteristics of human tactile receptors.

Artificial tactile feeling displayed by large displacement MEMS actuator arrays

We demonstrate display of artificial tactile feeling using large displacement MEMS actuator arrays. Each actuator consists of a piezoelectric actuator and hydraulic displacement amplification mechanism (HDAM) that encapsulates incompressible liquid in a micro-chamber with two flexible polymer membranes. In prior work, we experimentally applied the actuator arrays to an efficient vibrational Braille code display. In this paper, we investigated the artificial tactile feeling projected onto the fingertip in contact with the display while the actuation pattern was controlled both temporally and spatially. The arrays could successfully display “rough” and “smooth” tactile feeling distinctly when the vibrational frequency of the individual actuator and switching time of the lines of actuators were controlled.

Vibrational Braille code display with MEMS-Based hydraulic diplacement amplification mechanism

We demonstrate an efficient vibrational Braille code display with large-displacement MEMS actuator arrays. The large displacement is realized by hydraulic displacement amplification mechanisms (HDAM). Static and dynamic characteristics of HDAM were investigated and 18- and 11-fold amplification were achieved in static and dynamic (at 70 Hz) actuation, respectively. We applied actuator arrays consisting of HDAM and piezoelectric actuators to Braille code display. Owing to the characteristics of finger tactile receptors being more sensitive to vibrational stimuli than static ones and the natural frequency of HDAM, vibrational actuation at 70 Hz, which required a low voltage of 30V for subjects to detect the code, were more efficient than static actuation, which required 65V, and vibrational actuation at other frequencies.

Surface texture and pseudo tactile sensation displayed by a MEMS-based tactile display

We demonstrate display of artificial tactile feeling using large displacement MEMS actuator arrays. Each actuator consists of a piezoelectric actuator and hydraulic displacement amplification mechanism (HDAM) that encapsulates incompressible liquid in a micro-chamber with two flexible polymer membranes. In prior work, we experimentally applied the actuator arrays to an efficient vibrational Braille code display. In this paper, we investigated the artificial tactile feeling projected onto the fingertip in contact with the display while the actuation pattern was controlled both temporally and spatially. The arrays could successfully display two relative tactile feelings, “rough” and “smooth”, distinctly when the vibrational frequency of the individual actuator and switching time of the lines of actuators were controlled. In addition, we found that pseudo tactile sensation appeared between the adjacent cells of the display while the two actuators were controlled to have identical vibrating frequencies. We experimentally deduced the conditions when the pseudo tactile sensation was generated and the “effective” resolution of the display was augmented. Pseudo tactile sensation would enable the display to transfer more variable tactile sensation and thus, information to the finger.