In this project, we developed a highly customizable soft robotic system for cilia research. Unlike existing artificial cilia, we provide a simple method to fabricate hundreds of customized magnetic cilia with programmable metachronal waves. This level of system integration and complexity was only accessible with computer simulations before. To prove the capability of this soft robotic platform, we experimentally confirm two major numerical findings of fluidic transport on cilia carpet (Osterman et. al., PNAS, 2011; Elgeti et. al., PNAS, 2013), for the first time. Furthermore, we show the metachronal waves can propel a soft robot inspired by giant African millipede. We believe this robotic platform provides a powerful tool to spark new discoveries in fundamental cilia research, as well as inspiring new soft robotic designs for biomedical applications.

Cardiac patches are engineered materials and tissues that can restore heart functions by delivering cardiac cells and other drugs locally on the epicardial surface. Recently, new functions have been introduced into the cardiac patches, making it a promising platform for advanced therapies and disease monitoring. However, existing cardiac patches cannot be actuated mechanically and provide significant support to native heart contraction, thus unsuitable to assist the heart’s pumping function. Here, we present a new type of cardiac patches that can potentially function as a ventricular assistive device. These magnetically active cardiac patches (MACPs) can mechanically compress the heart under external magnetic fields and assist heart pumping. Unlike current ventricular assist devices, the MACPs require no tether to connect to the external power sources, significantly reducing the infections rates and complications. In addition, MACPs provide physiologic pulsatile support and require no direct blood contact, further eliminating serious complications, typical for current ventricular assist devices. We show with in vitro experiments that the ejection fraction is up to 65%, which would show complete restoration of heart ejection. We believe this new concept has great potential for the treatment of heart failure and the development of future cardiac devices that can be remotely actuated.

Mobile microrobots are expected to transform bioengineering and therapeutics by precisely navigating in microchannels and performing minimally invasive treatments. The functionalities of these magnetic microrobots have grown substantially in recent years. However, delivery at specific target locations remains challenging. Freely swimming microrobots have relatively low speeds, and it is difficult to swim against the complex fluid flows inside the human body. Therefore, catheters remain the most reliable delivery platform, but they cannot be miniaturized to the micron scale because the required pumping pressure is prohibitively high to transport microcargoes, based on Hagen-Poiseuille’s law.
Here, we develop a new microscale biomedical delivery mechanism that overcomes these challenges, offering rapid transport of microparticles without the need of an enclosing lumen to keep particles concentrated together – just like kinesins walking along microtubules, the microcargoes actively walk outside along a thin filament via micro-patterned magnetic stepping stones.
The strong magnetic field gradient close to the micromagnets enables a firm dynamic anchoring and propulsion along the artificial microtubules with an unprecedented speed. The microrobots can even locomote against strong fluidic flows, which we have quantified with detailed experiments and theoretical modeling. We also discovered a collective motion effect, where many small magnetic particles can self-assemble and subsequently propel along the artificial microtubule together. This process marks a major increase in transport above a critical particle density, where particles essentially push each other forwards. Previous theoretical works showed that this collective effect could enhance cytoskeletal transport in cell biology, but experimental evidence was lacking until now. Finally, we demonstrated that this technology is capable of delivering numerous microparticles accurately at very high concentrations to a specific location inside a branching microfluidic channel network.
Since the Hollywood movie “Fantastic Voyage”, mobile micromachines that can navigate inside the body and cure diseases have been a Holy Grail for scientists and engineers. Despite the advances in imaging, materials, actuation, control, and navigation, it is still very challenging due to the high complexity of in vivo environments and low reliability of these processes. By introducing artificial microtubules, we believe these “micro-highways for microrobots” can provide an alternative solution to the free-swimming microrobots, bringing robust biomedical microtransport much closer to reality.

The idea of self-assembly from a simple chain is widely adopted to synthesize structures from nanometer scales DNA/RNA and protein peptides, which are driven by thermal fluctuation, and up to meter-long robotic snakes, which are driven by distributed motors. However, the implementation of this simple idea at the mesoscale (mm~cm) is still missing, due to the negligible thermal energy (~kT) and prohibitively difficult integration and control of miniaturized motors.
In this work, we presented a generalized method to synthesize functional assemblies at the mesoscale by combining magnetic and elastic energies stored in 3d printed soft-robotic chains (MaSoChains). This method overcomes a fundamental challenge in minimally invasive interventions, which is the size of the tools is limited by the inner diameter of the catheter sheath. We show that it is possible to repeatedly assemble and di-assemble programmable structures and devices at the tip of the catheter, and we further explored the unique features and evaluated their potential in various clinically-relevant situations. We believe this method can be further expanded and customized for a wide range of minimally invasive surgeries to provide less pain, faster recovery, and fewer infections for patients.