Remote-controlled microflow using light-controlled state transitions within DNA condensates has been reported by scientists from Institute of Science Tokyo, Japan. By switching between ultraviolet light (UV) and visible light irradiation, the researchers demonstrated that the novel DNA motifs containing azobenzene can dissociate or reassemble. Furthermore, localized photo-switching within a DNA liquid condensate generated two distinct directional motions. This study can fuel the development of innovative fluid-based diagnostic chips and molecular computers.
Advancements in micro- and nano-scale fabrication technologies have given rise to diverse micrometer-sized entities such as microgels and liposomes, which are widely utilized in therapeutic formulations and microfluidic sensors. The precise control of the structure and function permits the adoption of micro-scale objects in various applications. However, the remote controllability of miniaturized fluidic objects has not yet been realized.
A recent study by scientists from Institute of Science Tokyo (Science Tokyo), Japan, represents a significant step toward the development of remotely controllable microfluidic objects that are capable of performing mechanical actions. The research team comprised Professor Masahiro Takinoue and Specially Appointed Assistant Professor Hirotake Udono, both from the Department of Computer Science, along with Associate Professor Shin-ichiro M. Nomura from the Department of Robotics, Graduate School of Engineering, Tohoku University. Their research findings were published online in Nature Communications on May 14, 2025.
In their study, the researchers utilized photoresponsive DNA liquid condensates that contained azobenzene (Azo)—a photo-reactive compound. Three single-stranded DNA strands self-assembled via complementary base-pairing of nucleotides to form distinctive 'Y'-shaped nanostructures (Y-motifs). Azobenzene was incorporated into the terminal overhangs of the Y-motif, or 'sticky ends,' to form photoresponsive DNA motifs.
"Previous studies have reported the photo-regulated state transitions of self-assembled DNA structures. However, no study has achieved any significant mechanical actions using them. Through our study, we have demonstrated remote-controlled microflow using photoresponsive DNA condensates," remarks Takinoue, highlighting the novelty of the present study.
By switching between ultraviolet light (UV) and visible light irradiation, the scientists demonstrated that the DNA motifs dissociate or reassemble reversibly. Interestingly, the light-induced changes in the motif binding state led to a reversible change in fluidity, from a gel to liquid or dissociated states, and vice versa. To create microflows using the fabricated DNA motifs, a non-photoresponsive motif without azobenzene was crosslinked to a photoresponsive DNA structure. The sticky end of the non-photoresponsive motif contained an orthogonal DNA sequence. "This cross-linking enabled mechanical actions by the photoresponsive DNA condensate on the non-photoresponsive DNA condensate," comments Takinoue.
During further experiments, the scientists discovered multiple modes in the photo-generated mechanical actions. Initially, a fast, diffusion-like outward spread of DNA condensates was detected when irradiated with UV light. Further, a UV-induced gel-to-liquid state transition called collapse mode was observed in condensates with a different DNA sequence. Remarkably, by alternating between UV and visible light, a 'spread and collect' mode signaling a reversible phase transition from a liquid-to-dissociated state, followed by reassembly into liquid DNA, was demonstrated by the researchers.
To show their application toward directional motion, an eagerly aspired robotic actuation, localized UV–visible photo-switching focusing on a fraction of the condensate was performed, resulting in two distinct directional motions of the DNA liquid condensates. "At lower switching frequencies, the DNA condensate can swim like a jellyfish, and at higher frequencies, the condensate can be pulled by its localized cycle flow, reminiscent of Pac-Man's motion," states Takinoue.
In summary, this study shines light on remote-controlled mechanical actions in DNA-based micro-assemblies. The potential applications of these novel DNA condensates include intelligent fluid-based diagnostic chips and fluid-type molecular computers.
