Multifunctional 3D‐Printed Pollen Grain‐Inspired Hydrogel Microrobots for On‐Demand Anchoring and Cargo Delivery

Abstract

development and implementation of such mobile medical microrobots, including fabrication of soft robotic microdevices, [11,12] synthesis of biocompatible or responsive (adaptive) materials, [13][14][15] and strategies for locomotion inside the body. [16][17][18][19][20][21][22] A myriad of remotely controlled medical microrobots has been proposed to enable shape change, multifunctionality, and reconfiguration in response to different stimuli, such as magnetic fields, [23][24][25][26][27] temperature, [28,29] chemical, [30,31] light, [32] and ultrasound, [33,34] for diverse medical applications, such as target drug delivery, minimally invasive surgery, and remote sensing. [35,36] However, microrobot interaction with biological tissues, complex biofluidic environments, and overlap of multiple stimuli are major challenges toward their future medical applications. [37] The operation of the untethered microrobots is limited in the human body, which is composed of complex physiological environments with a myriad of stimuli, which might trigger non-desired actuation with non-desired function. [38,39] Without decoupled multifunctionality (multifunctional structures), multi-input stimuli of the robot's responsive structures overlap each other, resulting in a partial loss of substantial functional capabilities. [40] In order to avoid the interrupted actuation, decoupling the multiple stimuli inputs is crucial by making each stimulus respond for a single function only. In addition to decoupling multifunctionality, achieving controllable attachment to soft biological tissues is essential for many target implementations, such as collecting bio-signals, applying electrical signals to nerves, and delivering drugs at targeted locations for given durations. [41][42][43][44] However, current designs of micro-scale robots have put more weight on steering and locomotion, so they possess relatively simple surface morphology and lack certain functions, such as tissue attachment ability. [45,46] Inspired by nature, there has been a wide range of biological materials with a variety of morphological structures, which have given us possible solutions to numerous engineering challenges. [47][48][49][50] Among them, pollen grain is emerging as an alternative to adhesive structures for targeted drug delivery applications due to their unique nanospike-like morphology and large inner cavity structure. [51][52][53] Despite the development of pollen graininspired material applications, a majority of the suggested structures have been made from natural pollen grain composed While a majority of wireless microrobots have shown multi-responsiveness to implement complex biomedical functions, their functional executions are strongly dependent on the range of stimulus inputs, which curtails their functional diversity. Furthermore, their responsive functions are coupled to each other, which results in the overlap of the task operations. Here, a 3D-printed multifunctional microrobot inspired by pollen grains with three hydrogel components is demonstrated...

Microrobots for Biomedicine: Unsolved Challenges and Opportunities for Translation

“…55,58−60 Swarming allows for the localized movement of large amounts of microrobots, which could improve both imaging capabilities and payload delivery. 61 One final opportunity is to engineer microrobots that remain at target sites by utilizing microrobots with high surface areas, 62 adhesive surface coatings, 63 or responsiveness to stimuli to promote robust physical interactions with target tissues, 43,64 to better tolerate biological clearance mechanisms, such as strong fluid flow. 43,64,65 We also believe that there is an opportunity to show that microrobots perform in a manner superior to traditional microor nanoparticles in drug delivery, something that has not yet been adequately investigated by the community.…”

“…61 One final opportunity is to engineer microrobots that remain at target sites by utilizing microrobots with high surface areas, 62 adhesive surface coatings, 63 or responsiveness to stimuli to promote robust physical interactions with target tissues, 43,64 to better tolerate biological clearance mechanisms, such as strong fluid flow. 43,64,65 We also believe that there is an opportunity to show that microrobots perform in a manner superior to traditional microor nanoparticles in drug delivery, something that has not yet been adequately investigated by the community. By showing that microrobots can accumulate at target sites better than traditional (nonactive) particle systems and provide better mechanisms for controlling the release of drugs within those target sites, microrobots may be poised as a top contender for particle-based drug delivery systems.…”

“…Another promising opportunity to accelerate the therapeutic efficacy of microrobots is the use of robotic swarms. ,− Swarming allows for the localized movement of large amounts of microrobots, which could improve both imaging capabilities and payload delivery . One final opportunity is to engineer microrobots that remain at target sites by utilizing microrobots with high surface areas, adhesive surface coatings, or responsiveness to stimuli to promote robust physical interactions with target tissues, , to better tolerate biological clearance mechanisms, such as strong fluid flow. ,, …”

Soft, Stretchable, and Conductive Hydrogel Based on Liquid Metal for Accurately Facial Expression Monitoring

“…Wearable sensors are becoming increasingly popular due to their ability to convert a range of stimuli into electrical signals. These sensors exhibit promising applications in various fields, including soft robotics, [1][2][3] neuron probes, [4][5][6] flexible sensors, [7][8][9][10] human-machine interfaces, [11][12][13][14] and other areas. [15][16][17][18] Recent DOI: 10.1002/admt.202300406 advancements in flexible electronics prove that wearable sensors can conform to the dynamic and curvy surfaces of the human body, making it possible to monitor physiological signals.…”

Individually Tailored Modular “Egg” Hydrogels Capable of Spatiotemporally Controlled Drug Release for Spinal Cord Injury Repair

“…[6] Lee et al created pH-responsive 3D-printed microrobots containing poly-Nisopropylacrylamide acrylic acid structures with an on-demand cargo release capability. [7] Controlling the drug release in hydrogels in response to internal signal activation was a promising application prospect. Nevertheless, as the injured environment in situ is typically highly heterogeneous and varies among individuals, the reliance on the inherent physical and biological features to govern medication distribution and release may have certain limits.…”