Three dimensional printing of metamaterial embedded geometrical optics(MEGO)

Three-dimensional printers have revolutionized many scientific fields with its low-cost,accessibility and ease of printing.In this paper,we show how stereolithography(SLA)based 3D printers can enable realization of innovative 3D optical devices formed through the fusion of metamaterials with geometrical optics or MEGO.It utilizes a combination of desktop SLA 3D printer and metal deposition/coating systems.Using this approach,we present innovative metamaterial embedded optical components such as mushroom-type metamaterials,curved wide-angle metamaterial absorbers/reflectors and a frequency selective moth eye hemispherical absorber.Finally a unique MEGO device formed through the fusion of a frequency selective metamaterial with an optical parabolic reflector has been demonstrated that combines their individual properties in a single device.The fabricated MEGO devices operate in the millimeter wave frequency range.Simulation and measurement results using terahertz continuous-wave spectrometer validate their functionality and performance.With improving resolution in 3D printing,MEGO devices will be able to reach Terahertz and optical frequencies in the near future.

Thread-based multiplexed sensor patch for real-time sweat monitoring

Sensor platforms that exploit the fibrous textile threads as substrates offer great promise since they can be directly sewn,woven or stitched on to any clothing.They can also be placed directly in intimate contact with the skin.In this work,we present a thread-based sensing platform in the form of a multiplexed sensing patch for continuous simultaneous on-skin monitoring of sweat.The patch performs real-time,on-body measurements of important biomarkers present in sweat such as electrolytes(sodium and ammonium ions),metabolites(lactate)and acidity(pH).Flexible threads coated with conductive inks were used as sensing electrodes.Selective potentiometric detection of electrolytes and pH was made possible through ion-selective membrane deposition and pH-sensitive polyaniline coating on threads,respectively.An amperometric enzymatic sensing scheme with lactate oxidase was used for the detection of lactate.An array of the thread sensors is integrated onto a patch with connectivity to a miniaturized circuit module containing a potentiostat,microprocessor and wireless circuitry for wireless smartphone readout.Extensive in vitro validation and an in vivo human pilot study involving a maximal exertion test show the promise of this platform for real-time physiological monitoring of human performance/fitness under stress,as well as diagnostic monitoring through sweat analysis.

Low-cost and cleanroom-free fabrication of microneedles

We present a facile,low-cost and cleanroom-free technique for the fabrication of microneedles using molds created by laser ablation.Microneedle mold with high aspect ratios is achieved on acrylic sheet by engraving a specific pattern of crossover lines(COL)using CO2 laser cutter.Ablating COL pattern on the acrylic sheet creates a sharp conical shape in the center of the design.We have shown that a variety of microneedle shapes with different heights and tip angles can be easily achieved by changing the number and the length of the COL.Polydimethylsiloxane(PDMS)microneedles were fabricated by casting the PDMS on the mold.The resulted PDMS microneedles are oxygen plasma treated and then silanized.Another PDMS layer is casted on PDMS microneedles and detached after curing.The silanization prevents those two layers of PDMS from bonding to each other and makes them easily detachable.After detachment of the PDMS mold of microneedles,the mold is used to fabricate degradable polyvinyl alcohol microneedle patch suitable for transdermal drug delivery.The release kinetics of the needles are also shown and discussed in order to prove the applicability of the needles.