Highly stretchable and sensitive unidirectional strain sensor via laser carbonization
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We present a simple and low-cost technique for fabricating highly stretchable (up to 100% strain) and sensitive (gauge factor of up to 20 000) strain sensors. Our technique is based on transfer and embedment of carbonized patterns created through selective laser pyrolization of thermoset polymers, such as polyimide, into elastomeric substrates (e.g., PDMS or Ecoflex). Embedded carbonized materials are composed of partially aligned graphene and carbon nanotube (CNT) particles and show a sharp directional anisotropy, which enables the fabrication of extremely robust, highly stretchable, and unidirectional strain sensors.
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Direct Laser Writing of Porous-Carbon/Silver Nanocomposite
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We demonstrate a facile method for the fabrication of porous-carbon/silver nanocomposites using direct laser writing on polymeric substrates. Our technique uses a combination of CO2 laser-induced carbonization and selective silver deposition on a polyimide sheet to create flexible highly conductive traces. The localized laser irradiation selectively converts the polyimide to a highly porous and conductive carbonized film with superhydrophilic wettability. The resulting pattern allows for selective trapping of aqueous silver ionic ink solutions into the carbonized regions, which are converted to silver nanoparticle fillers upon an annealing step.
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Highly Stretchable Potentiometric pH Sensor Fabricated via Laser Carbonization
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We report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline as the conductive filler, binding material, and pH-sensitive membrane.
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Laser treated glass platform with rapid wicking-driven transport
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Wicking and particle separation are two required capabilities for many microfluidics and lab-on-a-chip devices, but they often require multiple materials and structures (e.g., paper, polymer filters) which are difficult to integrate with established microfabrication techniques and materials. In this work, we combine both properties into a single glass platform with a straightforward and economical fabrication process. By laser machining soda lime glass with a specific power and laser speed, we create channels defined by an array of micro cracks (3-4 μm) which provide particle separation properties and simultaneously enable rapid liquid transport (up to 24.2 mm/s) as a result of capillary forces from the crevices and laser-induced surface hydrophilization.
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Laser ablation of metallized paper for inexpensive paper-based sensors
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We present a facile, mask-free, and rapid process for creating low-cost sensors on paper substrates by laser ablating commercially available metallized papers (MP), a non-toxic and eco-friendly commodity often used for decorative and food packaging purposes. This method provides a simple and scalable alternative to conventional photolithography-based processes and printing technologies. We use lasers to selectively remove nanometer thick aluminum films from the surface of the paper substrate and systematically measure the required threshold laser energy needed to remove the metal/polymer coating from the MP without damaging the mechanical structure and inherent hydrophilic/hygroscopic properties of the paper substrate.
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