Ultra-durable rotary micromotors assembled from nanoentities by electric fields

Abstract

Recently, we reported an innovative type of micromotors consisting of nanowires as rotors and patterned Au/Ni/Cr nanodisks as bearings. The dimensions of micromotors were less than 1 µm, and could continuously rotate for 15 hours over 240,000 cycles. To understand the limitation of their lifetime, we systematically investigated the rotation dynamics by analytical modeling and determined the time-dependent torques and forces involved in the rotation. From the forces and torques, the extent of wear of micromotors was successfully derived, which well agreed with the experimental characterizations. The results also proved that frictional force linearly increases with the loading in such rotary nanodevices operating in suspension, consistent with the prediction of the non-adhesive multi-asperity friction theory. With these understandings, we enhanced the design of micromotors and achieved an operation lifetime of 80 hours and over 1.1 million total rotation cycles. This research, shining new light on the frictional mechanism of recently reported nanowire micromotor with demonstration of the most durable rotary nanomechanical devices of similar dimensions to the best of our knowledge, can be inspiring for innovative design of future nanomechanical devices with ultralong lifetime for practical applications.

Man-made rotary nanomotors: a review of recent developments

“…15 The lifetime can reach 80 hours with over 1.1 million cycles. 55 Physical-field-driven rotary nanomotors are also advantageous in the overall biocompatibility and facileness in device integration. In the following discussion, we will categorize rotary nanomotors according to the employed external fields including the magnetic, optical, and electric fields.…”

“…19,138 Recently, it was demonstrated that nanomotors built from magnetic bearings with Au as the top layers can continuously rotate for 15 – 43 hours or over 240,000 – 500, 000 cycles in total. 15,55 With understanding of the interfacial wear problem at the contact point of the rotors and bearings, Ti was used as the top layer of the bearings replacing Au, which substantially enhanced the lifetime of the nanomotors to 80 hours over 1.1 million cycles [Figure 7(E)]. 55 The improvement can be attributed to the higher resistance of Ti to abrasion and deformation compared to that of Au.…”

“…15,55 With understanding of the interfacial wear problem at the contact point of the rotors and bearings, Ti was used as the top layer of the bearings replacing Au, which substantially enhanced the lifetime of the nanomotors to 80 hours over 1.1 million cycles [Figure 7(E)]. 55 The improvement can be attributed to the higher resistance of Ti to abrasion and deformation compared to that of Au.…”

“…Reproduced from Ref. 55 with permission from The Royal Society of Chemistry. (F) Illustrations of the nanomotors with the (i) chopsticks; (ii) perpendicular; and (iii) T-shaped magnetic configurations depending on the relative magnetic orientations of the nanowires and the patterned magnets.…”

Electrically Controlled Biochemical Release from Micro/Nanostructures for in vitro and in vivo Applications: A Review

“…Furthermore, nanomotors of a similar design have been demonstrated to rotate at a speed of 18,000 rpm. The operation of the nanomotors was ultra‐durable, continuing for 80‐hours and over 1.1 million cycles . These remarkable performances and the advantage of precision location of the nanomotors and real‐time monitoring of biomolecules as shown in Figure G−I, make this biochemical release technique promising for unprecedented applications in single cell biology.…”