Jungwook Paek

Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes

Microscale soft-robots hold great promise as safe handlers of delicate micro-objects but their wider adoption requires micro-actuators with greater efficiency and ease-of-fabrication. Here we present an elastomeric microtube-based pneumatic actuator that can be extended into a microrobotic tentacle. We establish a new, direct peeling-based technique for building long and thin, highly deformable microtubes and a semi-analytical model for their shape-engineering. Using them in combination, we amplify the microtube’s pneumatically-driven bending into multi-turn inward spiraling. The resulting micro-tentacle exhibit spiraling with the final radius as small as ~185 μm and grabbing force of ~0.78 mN, rendering itself ideal for non-damaging manipulation of soft, fragile micro-objects. This spiraling tentacle-based grabbing modality, the direct peeling-enabled elastomeric microtube fabrication technique, and the concept of microtube shape-engineering are all unprecedented and will enrich the field of soft-robotics.

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides

High aspect-ratio micropillars are in strong demand for microtechnology, but their realization remains a difficult challenge, especially when attempted with soft materials. Here we present a direct drawing-based technique for fabricating micropillars with poly(dimethylsiloxane). Despite the materials extreme softness, our technique enables routine realization of micropillars exceeding 2,000 μm in height and 100 in aspect-ratio. It also supports in situ integration of microspheres at the tips of the micropillars. As a validation of the new structures utility, we configure it into airflow sensors, in which the micropillars and microspheres function as flexible upright waveguides and self-aligned reflectors, respectively. High-level bending of the micropillar under an airflow and its optical read-out enables mm s(-1) scale-sensing resolution. This new scheme, which uniquely integrates high aspect-ratio elastomeric micropillars and microspheres self-aligned to them, could widen the scope of soft material-based microdevice technology.

A bioinspired microfluidic model of liquid plug-induced mechanical airway injury

Occlusion of distal airways due to mucus plugs is a key pathological feature common to a wide variety of obstructive pulmonary diseases. Breathing-induced movement of airway mucus plugs along the respiratory tract has been shown to generate abnormally large mechanical stresses, acting as an insult that can incite acute injury to the airway epithelium. Here, we describe a unique microengineering strategy to model this pathophysiological process using a bioinspired microfluidic device. Our system combines an air-liquid interface culture of primary human small airway epithelial cells with a microengineered biomimetic platform to replicate the process of mucus exudation induced by airway constriction that leads to the formation of mucus plugs across the airway lumen. Specifically, we constructed a compartmentalized three-dimensional (3D) microfluidic device in which extracellular matrix hydrogel scaffolds reminiscent of airway stroma were compressed to discharge fluid into the airway compartment and form liquid plugs. We demonstrated that this plug formation process and subsequent movement of liquid plugs through the airway channel can be regulated in a precisely controlled manner. Furthermore, we examined the detrimental effect of plug propagation on the airway epithelium to simulate acute epithelial injury during airway closure. Our system allows for a novel biomimetic approach to modeling a complex and dynamic biophysical microenvironment of diseased human airways and may serve as an enabling platform for mechanistic investigation of key disease processes that drive the progression and exacerbation of obstructive pulmonary diseases.

Minimally Intrusive Optical Micro-Strain Sensing in Bulk Elastomer Using Embedded Fabry-Pérot Etalon

A variety of strain sensors have been developed to measure internal deformations of elastomeric structures. Strain sensors measuring extremely small mechanical strain, however, have not yet been reported due mainly to the inherently intrusive integration of the sensor with the test structure. In this work, we report the development of a minimally intrusive, highly sensitive mechanical strain transducer realized by monolithically embedding a Fabry-Pérot (FP) etalon into a poly(dimethylsiloxane) (PDMS) block test structure. Due to the extreme sensitivity of the FP resonance condition to the thickness of the spacer layer between the two reflectors, the limit of detection in the mechanical deformation can be as low as ~110 nm with a 632.8 nm laser used as the probing light. The compatibility of PDMS with additive fabrication turned out to be the most crucial enabling factor in the realization of the FP etalon-based strain transducer.

Corrigendum: Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes.

Corrigendum: Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes

Minimally Intrusive Optical Micro-Strain Sensing in Bulk Elastomer with Embedded Fabry-Perot Etalon

We demonstrate a minimally intrusive, highly sensitive optical strain transducer based on a Fabry-Perot etalon monolithically embedded into the elastomeric test structure. Using the extreme sensitivity of the etalon, we accomplished the limit of detection in the mechanical deformation as low as 110 nm.