Kate E. Laflin

Self-folding micropatterned polymeric containers

We demonstrate self-folding of precisely patterned, optically transparent, all-polymeric containers and describe their utility in mammalian cell and microorganism encapsulation and culture. The polyhedral containers, with SU-8 faces and biodegradable polycaprolactone (PCL) hinges, spontaneously assembled on heating. Self-folding was driven by a minimization of surface area of the liquefying PCL hinges within lithographically patterned two-dimensional (2D) templates. The strategy allowed for the fabrication of containers with variable polyhedral shapes, sizes and precisely defined porosities in all three dimensions. We provide proof-of-concept for the use of these polymeric containers as encapsulants for beads, chemicals, mammalian cells and bacteria. We also compare accelerated hinge degradation rates in alkaline solutions of varying pH. These optically transparent containers resemble three-dimensional (3D) micro-Petri dishes and can be utilized to sustain, monitor and deliver living biological components.

Laser triggered sequential folding of microstructures

In order to fabricate complex origami inspired devices, it is necessary to control folding pathways and enable sequential folding. We demonstrate sequential folding of microstructures from afar by the directed heating of pre-stressed hinges using low power, 40–80 mW handheld, commercial lasers. We observed that the hinge-actuation and consequently folding time varied with laser irradiance, wavelength, and distance. We highlight possible applications by sequential folding of patterned and nested microstructures.

Tetherless Microgrippers With Transponder Tags

We describe the concept of utilizing tetherless microstructured grippers with attached silicon (Si)-based chips for event-based gripping. Grippers were fabricated using photolithography, and Si chips were bonded to them using a solder-based directed assembly approach. Because we propose the use of these grippers as tags or to attach electronic devices to various surfaces, we also attached commercial microtransponder chips to the grippers as a specific example of an integrated and commercially available electronic device. After assembly, we released grippers with integrated chips from the substrate. Grippers closed upon exposure to heat (>; 40°C) or specific chemical environments that softened or degraded a polymer trigger layer incorporated within each hinge. We investigated gripping capabilities of chip-carrying grippers on woven textile fibers and a live caterpillar; these demonstrations were achieved without any attached wires or electrical power. The autonomous thermochemical closure response of the grippers coupled with convenient and secure attachment of wireless microtransponders is a step toward the creation of smart event-based gripping platforms with communication modules.

Biologic tissue sampling with untethered microgrippers.

Even with advances in non-invasive diagnosis of diseases such as cancer or inflammatory diseases, tissue biopsy coupled with histopathologic examination remains the gold standard in establishing an accurate diagnosis.1–2 Generally, effective tissue diagnosis is fundamentally based on biopsying lesions that are suspicious based on visual inspection. Nevertheless, numerous mucosal conditions, such as dysplasia in ulcerative colitis or Barrett’s esophagus, are not always readily recognizable visually, and thus mandate surveillance protocols that involve random biopsies.3 To effectively sample large organs such as the colon, numerous biopsies are required,4 which can be time consuming. Moreover, due to the size of current forceps and the associated mucosal trauma and to the serial operation of the forceps, the number of random biopsies that can be realistically carried out is limited. Consequently, the current standard of care for cancer surveillance in ulcerative colitis patients is performed with at least 33 sequential biopsies (4-quadrant biopsies every 10 cm), which we estimate cumulatively samples less than 0.3% of colonic mucosa. The low sampling coverage may be ineffective at detecting precancerous or cancerous lesions, especially for early, small lesions that are also the most treatable.

Initiation of nanoporous energetic silicon by optically-triggered, residual stress powered microactuators

The integration of energetic materials with chip-scale MEMS fabrication processes, and in particular the development of nanoporous energetic silicon (NES), is a promising path to provide significant quantities of energy for certain microscale applications. Here we demonstrate the low-power wireless initiation of an on-chip energetic reaction, by absorbing optical energy, transmitting mechanical energy, and releasing a large amount of chemical energy, without the use of any external wires or batteries. A novel actuator powered by residual thin film stress absorbed 25 W/cm2 of optical power from a 532 nm visible laser, heated, and released up to 22 nJ of mechanical energy. The mechanical energy was sufficient to initiate 6.7 mg of NES and release up to 66 J of chemical energy.