Acoustics-Actuated Microrobots

Abstract

Microrobots can operate in tiny areas that traditional bulk robots cannot reach. The combination of acoustic actuation with microrobots extensively expands the application areas of microrobots due to their desirable miniaturization, flexibility, and biocompatibility features. Herein, an overview of the research and development of acoustics-actuated microrobots is provided. We first introduce the currently established manufacturing methods (3D printing and photolithography). Then, according to their different working principles, we divide acoustics-actuated microrobots into three categories including bubble propulsion, sharp-edge propulsion, and in-situ microrotor. Next, we summarize their established applications from targeted drug delivery to microfluidics operation to microsurgery. Finally, we illustrate current challenges and future perspectives to guide research in this field. This work not only gives a comprehensive overview of the latest technology of acoustics-actuated microrobots, but also provides an in-depth understanding of acoustic actuation for inspiring the next generation of advanced robotic devices.

Ultrasound-guided medical procedures: a growing field with new opportunities

“…On the one hand, the expansion of classical ultrasound-guidance applications for "macroscopic" therapies (typically INVUS) can be expected, given the increasing availability of high-resolution as well as portable ultrasound systems and the growing interest in real-time fusion imaging-guided procedures. On the other hand, there are upcoming new ("smart") applications employing the various physico-chemical effects of ultrasound on a micro-and nano-therapeutic level (▶ Table 1) [34][35][36][37]. By combining different mechanisms of ultrasound (cavitation, acoustic streaming, ultrasound-induced vibration, acoustic scattering, and acoustic radiation forces) with creative system designs (e. g., bubble-based sensing, piezo-based sensing, nano-carriers, hydrogel carriers, sono-sensitizers, mechanosensitive proteins, fluid flow control, micro-and nano-robots) [36], unique capabilities have been realized for novel applications ranging from optical communication and imaging to targeted drug delivery and microsurgery [36,37].…”

“…Andererseits gibt es neue ("intelligente") Anwendungen, die die verschiedenen physikalisch-chemischen Effekte des Ultraschalls auf mikro-und nanotherapeutischer Ebene nutzen (▶ Tab. 1) [34][35][36][37]. Durch die Kombination diverser Ultraschallmechanismen (Kavitation, akustische Strömung, ultraschallinduzierte Vibration, akustische Streuung und akustische Strahlungskräfte) mit kreativen Systemdesigns (z.…”

“…On the other hand, there are upcoming new ("smart") applications employing the various physico-chemical effects of ultrasound on a micro-and nano-therapeutic level (▶ Table 1) [34][35][36][37]. By combining different mechanisms of ultrasound (cavitation, acoustic streaming, ultrasound-induced vibration, acoustic scattering, and acoustic radiation forces) with creative system designs (e. g., bubble-based sensing, piezo-based sensing, nano-carriers, hydrogel carriers, sono-sensitizers, mechanosensitive proteins, fluid flow control, micro-and nano-robots) [36], unique capabilities have been realized for novel applications ranging from optical communication and imaging to targeted drug delivery and microsurgery [36,37]. A recent cutting-edge animal model study investigated a microbubble-assisted ultrasound-guided immunotherapy of cancer (MUSIC), using nanocomplex-conjugated microbubbles that target antigen-presenting cells to effectively deliver cyclic dinucleotides into their cytosol via ultrasound-guided sonoporation; this resulted in the activation of highly effective local and systemic antitumor immune responses [38].…”

“…Durch die Kombination diverser Ultraschallmechanismen (Kavitation, akustische Strömung, ultraschallinduzierte Vibration, akustische Streuung und akustische Strahlungskräfte) mit kreativen Systemdesigns (z. B. bläschenbasierte Sensorik, piezobasierte Sensorik, Nanoträger, Hydrogelträger, Sono-Sensibilisatoren, mechanosensitive Proteine, Flüssigkeitsströmungs-Lenkung, Mikro-und Nanoroboter) [36] wurden einzigartige Möglichkeiten für neuar-tige Anwendungen geschaffen, die von optischer Kommunikation und Bildgebung bis hin zu gezielter Medikamentenabgabe und Mikrochirurgie reichen [36,37]. Eine aktuelle bahnbrechende Studie am Tiermodell untersuchte eine mikrobläschen-gestützte ultraschall-geführte Immuntherapie des Karzinoms (MUSIK), unter Verwendung von nanokomplex-konjugierten Mikrobläschen, die an antigen-präsentierende Zellen binden und via ultraschall-gezielte Sonoporation zyklische Dinukleotide in deren Zytosol abgeben; dies führte zur Aktivierung hocheffektiver lokaler und systemischer Immunreaktionen gegen den Tumor [38].…”

Light-driven microrobots: capture and transport of bacteria and microparticles in a fluid medium

“…Microrobots that can swim in various fluid mediums autonomously under the control of different external energy sources have gained a considerable amount of interest among researchers in recent years. [1][2][3][4][5][6][7][8] Considering their precise swimming and controlled activities, they have been proposed to be a potential candidate for important applications like targeted drug delivery, 9,10 cell treatment, [11][12][13][14] bacteria capturing and sensing, [15][16][17][18][19][20][21] cargo transport in lab-on-a-chip devices, 22,23 environmental remediations, [24][25][26] etc. In the progress to address these applications, several microrobot designs have been proposed.…”