4D Printing of Plasmon‐Encoded Tunable Polydimethylsiloxane Lenses for On‐Field Microscopy of Microbes

Abstract

handheld, and in field-portable, enabling a spatiotemporal mapping of the microbiome potentially leading to unprecedented insight into human health and environment conditions. [1] Smartphone-based optical/fluorescence microscopy leverage the scaling down of lens/filter optical components and the computational/networking capabilities of smartphones. [1][2][3][4] These platforms have proved to be very effective for biomedical applications. Nonethless, the cost of manufacturing of miniaturized optical components, i.e., the lenses and filters, for the assembling of add-on optical modules for smartphones with reduced size and weight (yet, hundreds of grams and of cm 3 ) has hampered the diffusion of smartphone-based microscopy to date. [5] To circumvent these limitations researchers have developed strategies to fabricate polymeric (e.g., polydimethylsiloxane, PDMS) magnifying lenses that can be directly attached to the smartphone camera to boost intrinsic magnification and resolution performance. [6][7][8] These strategies include hanging droplet of uncured PDMS deposited by inkjet printing on heated flat surface; [6] moldless thermal curing of PDMS droplet prepared using a moving needle extruder; [7] drop-casting of uncured PDMS droplet onto a smooth circular disk of poly(methyl methacrylate); [8] moldless printing of uncured PDMS droplet using nanostructured porous silicon (PSi) as templating layer. [5] In two cases the polymeric lens also embedded a rejection optical filter that enabled performing smartphone-based fluorescence microscopy leveraging image magnification and light rejection properties of the lens. [5,9] In Ref. [9], the lens-filter element was prepared mixing PDMS prepolymer with dyes featuring high absorbance in specific wavelength regions. The lens was coupled to a smartphone and used in several bioanalytic applications, namely, cell and tissue observation, cell counting, and plasmid transfection evaluation. [9] In Ref.[5], a nanostructured porous silicon oxide (PSiO 2 ) filter, namely, a distributed Bragg reflector (DBR) with stopband tuned to reject light in a selected wavelength region, was integrated into the PDMS lens. The lens-filter element was coupled to a smartphone and used for the fluorescence imaging and counting of CAOV-3 ovarian cancer cells in a conventional live/dead assay. [5] Very recently our research group developed a fluorideassisted chemical route for the in-situ synthesis of metal nanoparticles (NPs) on PDMS. [10] In contrast to conventional in Here the 4D printing of a magnifying polydimethylsiloxane (PDMS) lens encoded with a tunable plasmonic rejection filter is reported. The lens is formed by moldless printing of PDMS pre-polymer on a nanostructured porous silicon (PSi) templating layer. A nanometer-thick plasmonic filter is integrated on the lens surface by in situ synthesis of Ag and Au nanoparticles (NPs) with programmed density. The filter can be designed to reject light at the plasmonic resonance wavelength of the NPs with an optical density tunable from 0 to 3 and re...

Wireless and Flexible Optoelectronic System for In Situ Monitoring of Vaginal pH Using a Bioresorbable Fluorescence Sensor

“…PDMS was chosen for the ring fabrication due to its wellknown biocompatibility, flexibility, and transparency. [34] Moreover, PDMS can be easily functionalized with silver nanoparticles (AgNPs) [43][44][45] with bactericidal properties, [46][47][48] which helps safe management of the vaginal ring before, during, and after use.…”

In situcontrolled and conformal coating of polydimethylsiloxane foams with silver nanoparticle networks with tunable piezo-resistive properties

“…AgNPs are formed on the PDMS surface by in situ redox reaction occurring between unreacted Si-H bonds (of the curing agent) available at the PDMS surface and metallic cations Ag + available in the solution. 6,7 Eventually, the AgNP-decorated foam was thoroughly rinsed with ethanol and dried (Fig. 1a.3).…”

“…1,2 Thus, controlling the size and distribution of NPs on the hosting material is crucial to provide access to novel optical, electrical, and mechanical functionalities. [3][4][5][6][7] This is even more challenging on polymer foams, for which the conformal coating of the inner surface of the pore network with NPs is further required. The scarce control of the collective organization of NPs on polymeric materials achieved with state-of-the-art approaches has hampered the optimization of nanocomposite functionalities to date.…”

Biocompatible Gel-Free Coconut Oil and Carbon Black Electrodes for ECG and Respiration Measurements

“…The material can withstand large strain values as well as repetitive stretching, remaining effective even after being elongated by 100 % for 100 cycles. The material has electrical properties and a structure comparable to that of tunnable piezo-resistive polymer foams with limited elasticity (<60%) [20], [33], [34]. The electrodes have demonstrated to be suitable to measure ECG signals and impedance pneumography without the need for contact enhancer or conductive gels.…”