Compact Digital Microrobot Based on Multistable Modules

Abstract

Current digital microrobots are mainly composed of bistable modules and flexible structures. Unlike conventional microrobots, they are based on mechanical stability instead of complex control strategies in order to reach precise and repeatable discrete positioning. By design, their number of stable positions depends on the number of bistable modules. As a consequence, increasing the robot workspace requires using several modules. In this case, the robot size increases and its miniaturization becomes complex and non-intuitive. To address this issue, a multistable module has been developed to reach several stable positions. In this paper, a new generation of digital microrobots is proposed. Based on two multistable modules and flexible structures, the new microrobot can reach a large workspace while having a small footprint. Concretely, the robot size decreases by 26% while the number of stable positions increases by 950% in comparison with the first generation of the digital microrobot. A prototype is designed, fabricated and characterized experimentally. Preliminary results show a good agreement between the expected and the achieved workspace. The robot achieves 169 stable positions with a discrete step of 4.125 µm and a resolution of 150 nm. With these capabilities, the robot paves the way for promising perspectives and applications, in particular precise micro-manipulation in confined environment such as a Scanning Electron Microscope.

Accurate Sensorless Multistable Microsystem With a Single Actuator

“…Bistability represents the simplest case of multistability, and thin beam bistable mechanisms, with curved or inclined forms, are the most commonly used types of bistable mechanisms in microsystems (Hussein et al, 2015;Hussein et al, 2019;Hussein et al, 2020c;Hussein et al, 2020b;Hussein and Younis, 2020;Cao et al, 2021). Multistable micro-mechanisms are based on the assembly of elementary mechanisms with a small degree of multistability, either in series (Gerson et al, 2012;Zhang et al, 2015) or parallel (Chalvet et al, 2013;Che et al, 2016;Hua et al, 2019;Mohand-Ousaid et al, 2021), or on a mobile part actuated based on stepping mechanisms (Arthur et al, 2011;Hussein et al, 2018).…”

“…Multiple bistable modules were introduced in parallel in a complete monolithic microsystem to switch a mobile part between multiple stable positions in a planar discrete workspace (Chalvet et al, 2013). Moreover, a multistable module based on the stepping principle was developed to replace all the bistable modules in the previous design (Hussein, 2015;Bouhadda et al, 2018;Hussein et al, 2018;Mohand-Ousaid et al, 2021). Notably, the use of multistable modules based on the stepping principle increased the number of stable positions, decreased the size of the structure and number of internal components, increased the accuracy of stable positions, and enabled more robust fabrication, easier control, and faster switching with a lower energy consumption.…”

“…The elimination of sensors simplifies the device structure and enhances the control and power delivery schemes. Such frameworks can enable more efficient miniaturization and operation in small environments and enclosed spaces (Chen et al, 2011;Chalvet et al, 2013;Hussein, 2015;Hussein et al, 2018;Mohand-Ousaid et al, 2021).…”

“…Considering this aspect, this paper proposes a sensorless and monolithic multistable microsystem with a compact stepping mechanism. As compared with other multistable microsystems (Chalvet et al, 2013;Hussein et al, 2018;Hwang and Arrieta, 2018;Hua et al, 2019;Zanaty et al, 2019;Gorissen et al, 2020;Jeong et al, 2020;Ramakrishnan and Frazier, 2020;Mohand-Ousaid et al, 2021) and stepping actuators (Pai and Tien, 2000;Yeh et al, 2002;Tas et al, 2003;De Boer et al, 2004;Maloney et al, 2004;Oak et al, 2011;Penskiy and Bergbreiter, 2013;Contreras and Pister, 2017), the novel design of the multistable microsystem exploits the advantages of digital microbotics, in which the mobile part can be accurately placed at multiple stable positions without implementing sensors. Furthermore, the actuation dexterity is enhanced by using only a single actuator to move the mobile part in two directions and hold it in multiple stable positions.…”

Solving the inverse kinematics problem of discretely actuated hyper-redundant manipulators using the multi-module searching method

“…Today researchers use discrete actuators in a variety of fields and devices such as grippers [3][4][5][6][7][8][9], switches [10], medical imaging devices [11][12][13], exoskeleton rehabilitation robots [14,15], solar centralizing mirrors [16,17], millirobots [18], microrobots [19][20][21], and soft robots [22][23][24][25]. Some investigators use discrete actuators in hyper-redundant manipulators [2,[26][27][28][29].…”