Assembly of Fillable Microrobotic Systems by Microfluidic Loading with Dip Sealing

Abstract

applications, including diagnostics and therapeutics. [1] Compared to traditionally passive nanomedicines, microrobots are active-matter systems composed of actuatable components including magnetic, [2] acoustic, [3] chemical, [4] and/or materials of biological origin. [5] These properties enable microrobots to navigate their environments and to perform highly specific tasks, such as penetrating deep tissues for drug delivery. Importantly, microrobotic systems can be engineered to perform different functions including targeted drug delivery, [6] cell delivery, [7] sensing, [8] and imaging. [9] However, the human body consists of complex microenvironments with varying pH levels, pressures, and size constraints. Designing microrobots with properties that permit navigation through complex environments like the body while maintaining efficacy is a multifaceted challenge.Surface coatings are widely used as a direct approach for loading cargoes onto microrobots. These coatings capitalize on the interface forces between the microrobotic devices and the loaded cargoes and can be released in response to exogenous or endogenous stimuli. For instance, hydrogen bonding has been employed to non-covalently attach surface-loaded drug cargoes that can then be released via Microrobots can provide spatiotemporally well-controlled cargo delivery that can improve therapeutic efficiency compared to conventional drug delivery strategies. Robust microfabrication methods to expand the variety of materials or cargoes that can be incorporated into microrobots can greatly broaden the scope of their functions. However, current surface coating or direct blending techniques used for cargo loading result in inefficient loading and poor cargo protection during transportation, which leads to cargo waste, degradation and non-specific release. Herein, a versatile platform to fabricate fillable microrobots using microfluidic loading and dip sealing (MLDS) is presented. MLDS enables the encapsulation of different types of cargoes within hollow microrobots and protection of cargo integrity. The technique is supported by highresolution 3D printing with an integrated microfluidic loading system, which realizes a highly precise loading process and improves cargo loading capacity. A corresponding dip sealing strategy is developed to encase and protect the loaded cargo whilst maintaining the geometric and structural integrity of the loaded microrobots. This dip sealing technique is suitable for different materials, including thermal and light-responsive materials. The MLDS platform provides new opportunities for microrobotic systems in targeted drug delivery, environmental sensing, and chemically powered micromotor applications.

Direct laser writing-enabled 3D printing strategies for microfluidic applications

“…225 (b) DLW-printed microfluidic system with one inlet for (i)-(iii) loading "microrobots" (i.e., magnetic liquid-core-shell particles) for drug delivery applications. 226 (c) DLW-printed microfluidic system with two inlets for culturing cell spheroids as well as mouse cumulus-oocyte-complexes and embryos. 227 on the use of commercial DLW printers from Nanoscribe GmbH-the authors used a NanoOne DLW printer from the company, UpNano GmbH, but also because the researchers leveraged a recent innovation for increasing the efficiency of DLW printing processes: "Dynamic Optical Tuning (DOT)".…”

Recent Advances in Multi‐Photon 3D Laser Printing: Active Materials and Applications

“…For example, in 2022, Sun et al reported a procedure to print microcarriers that were filled through a microfluidic channel (see Figure 6A,B). [23] Filling of the carrier solution was possible after carefully designing the channels to control the surface tension, pressure, material waste, and connection between the system and the filling nozzle. After filling, the carriers were closed with a stimuli-responsive polycaprolactone sealing that released the encapsulated solution upon heating or NIR irradiation.…”

“…Adapted with permission. [ 23 ] Copyright 2023, The Authors. B) SEM cross‐section image of the drug carrier for the filling process.…”

“…Adapted with permission. [ 23 ] Copyright 2023, The Authors. C) SEM images of a bistable pneumatic actuator prepared by multi‐photon 3D laser printing on a glass capillary (bottom) in its two different states.…”

Spontaneous Separation of Immiscible Organic Droplets on Asymmetric Wedge Channels with Hierarchical Microchannels

“…Separating immiscible mixed liquids is a key step in pollutant treatment or resource recovery in daily life and industrial production. − These mixtures contain complex organic solutions with a much smaller surface tension difference than those of oil–water mixtures. Separation of immiscible mixed organic liquids has great demands in the fields of biomedical applications and industrial chemistry, but the separation methods considerably fall behind the application requirements. − Currently, very limited strategies have been introduced to separate these mixed organic liquids with low surface tension differences. − For example, Tie et al developed a versatile coating that regulates the wetting behavior of membranes by forming a stable liquid injection interface and separating mixed organic liquids .…”