Simultaneous Transfer and Imaging of Latent Fingerprints Enabled by Interfacial Separation of Polydopamine Thin Film

Emerging Optical Microscopy Techniques for Electrochemistry

An optical microscope is probably the most intuitive, simple, and commonly used instrument to observe objects and discuss behaviors through images. Although the idea of imaging electrochemical processes operando by optical microscopy was initiated 40 years ago, it was not until significant progress was made in the last two decades in advanced optical microscopy or plasmonics that it could become a mainstream electroanalytical strategy. This review illustrates the potential of different optical microscopies to visualize and quantify local electrochemical processes with unprecedented temporal and spatial resolution (below the diffraction limit), up to the single object level with subnanoparticle or single-molecule sensitivity. Developed through optically and electrochemically active model systems, optical microscopy is now shifting to materials and configurations focused on real-world electrochemical applications.

Micro-patterned cell populations as advanced pharmaceutical drugs with precise functional control

Human cells are both advanced pharmaceutical drugs and 'drug deliverers'. However, functional control prior to or after cell implantation remains challenging. Micro-patterning cells through geometrically defined adhesion sites allows controlling morphogenesis, polarity, cellular mechanics, proliferation, migration, differentiation, stemness, cell-cell interactions, collective cell behavior, and likely immuno-modulatory properties. Consequently, generating micro-patterned therapeutic cells is a promising idea that has not yet been realized and few if any steps have been undertaken in this direction. This review highlights potential therapeutic applications, summarizes comprehensively the many cell functions that have been successfully controlled through micro-patterning, details the established micro-pattern designs, introduces the available fabrication technologies to the non-specialized reader, and suggests a quality evaluation score. Such a broad review is not yet available but would facilitate the manufacturing of therapeutically patterned cell populations using micro-patterned cell-instructive biomaterials for improved functional control as drug delivery systems in the context of cells as pharmaceutical products.

Interpol review of fingermarks and other body impressions 2016-2019

This review paper covers the forensic-relevant literature in fingerprint and bodily impression sciences from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20 Review%20 Papers%202019. pdf.

Photocurable Urushiol Analogues Bearing Methacryloxy-Containing Side chains

Photocurable urushiol analogues were synthesized using eugenol (an ingredient of clove oil) as the starting material. Photo-induced radical polymerization with 2,2-dimethoxy-2-phenylacetophenone as a photo-initiator took place in the film prepared from the urushiol analogue-bearing methacryloxy groups at the ends of their side chains. Successful polymerization was confirmed by infrared spectroscopy measurements of the film before and after photo-irradiation. Strain-induced elastic buckling instability for mechanical measurement tests revealed that the Young's moduli of the photo-irradiated samples were 4-5 times higher than the films without photo-irradiation. This was attributed to the formation of a highly cross-linked structure through polymerization of the methacrylic moieties and oxidative polymerization of the catechol moieties. Photo-induced surface texturing was also performed for the films prepared on a substrate using a photomask. Negative-tone patterns were successfully obtained after development by soaking in cyclohexanone over several minutes. The preparation of such patterned surfaces was of particular relevance as the obtained surface can serve as a scaffold for cell adhesion, protein immobilization, and the immobilization of other chemicals with spatial disposition.

Robust Conductive Micropatterns on PTFE Achieved via Selective UV-Induced Graft Copolymerization for Flexible Electronic Applications

Fabrication of stable and functional patterns on the surface of PTFE remains a great technical challenge owing to its inertness and high hydrophobicity. Here, we report for the first time the fabrication of functional micropatterns on the PTFE surface by selectively irradiating plasma-treated PTFE coated with the monomer solution. A series of uniform highly dense poly(dopamine methacrylamide) (denoted as PDMA) line patterns with line/pitch widths of 20/20 and 50/50 μm are fabricated on the surface of PTFE (denoted as PDMA-p/PTFE) using dopamine methacrylamide (DMA) as the monomer. Surface graft copolymerization occurs and is attributed to the universal adsorption of DMA and the low grafting energy barrier, compared with the polymerization energy barrier, which is also demonstrated by the DFT calculations. Further, robust well-defined metal Ag or Cu patterns with strong adhesion strength are fabricated on the surface of the PTFE film by electroless deposition and are demonstrated for applications in flexible electronics. The approach is demonstrated to be versatile for fabrication of PDMA micropatterns onto a wide range of polymeric substrates, including polypropylene and acrylonitrile butadiene styrene.

Patterning Hydrophobic Surfaces by Negative Microcontact Printing and Its Applications

Here, a negative microcontact printing method is developed to form hydrophilic polydopamine (PDA) patterns with micrometer resolution on hydrophobic including perfluorinated surfaces. In the process of the negative microcontact printing, a uniform PDA thin film is first formed on the hydrophobic surface. An activated polydimethylsiloxane (PDMS) stamp is then placed in contact with the PDA-coated hydrophobic surface. Taking advantage of the difference in the surface energy between the hydrophobic surface and the stamp, PDA is removed from the contact area after the stamp release. As a result, a PDA pattern complementary to the stamp is obtained on the hydrophobic surface. By using the negative microcontact printing, arrays of liquid droplets and single cells are reliably formed on perfluorinated surfaces. Microlens array with tunable focal length for imaging studies is further created based on the droplet array. The negative microcontact printing method is expected to be widely applicable in high-throughput chemical and biological screening and analysis.

Development of Well-Preserved, Substrate-Versatile Latent Fingerprints by Aggregation-Induced Enhanced Emission-Active Conjugated Polyelectrolyte

The development of highly efficient latent fingerprint (LFP) technology remains extremely vital for forensic and criminal investigations. In this contribution, a straightforward, rapid, and cost-effective method has been established for the quick development of well-preserved latent fingerprint on multiple substrates, including plastic, glass, aluminum foil, metallic surfaces, and so forth, without any additional treatment, based on aggregation-induced enhanced emission-active conjugated polyelectrolyte (CPE) 3,3'-((2-(4-(1,2-diphenyl-2-(p-tolyl)vinyl)phenyl)-7-(7-methylbenzo[c][1,2,5]thiadiazol-4-yl)-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(1-methyl-1H-imidazol-3-ium) bromide, revealing clearly the third-level details (ridges, bifurcations, and pores) with high selectivity, high contrast, and no background interference even by blood stains, confirming the ability of the proposed technique for LFP detection with high resolution. The LFP development process was accomplished simply by immersing fingerprint-loaded substrate into the CPE solution for ∼1 min, followed by shaking off the residual polymer solution and then air drying. The CPE was readily transferred to the LFPs because of the strong electrostatic and hydrophobic interaction between the CPE molecules and the fingerprint components revealing distinct fluorescent images on various smooth nonporous surfaces.

Interfacial Separation-Enabled All-Dry Approach for Simultaneous Visualization, Transfer, and Enhanced Raman Analysis of Latent Fingerprints

It is of essential importance to visualize latent fingerprint (LFP) and analyze the compounds therein. For this purpose, various approaches have been developed but suffer from low imaging and/or detection efficiency. Most importantly, most of them require a necessary in-solution process and thus are not applicable to LFPs on bulky or water-sensitive substrates. In this work, we report an all-dry method to achieve simultaneous visualization and transfer of LFP and enhanced Raman analysis of multiple species therein. In this innovative approach, polydopamine (PDA) film-coated poly(dimethylsiloxane) (PDMS) flake with dense plasmonic silver nanoparticles (AgNPs@PDA@PDMS) was applied to cover the substrate carrying LFP. After gentle separation, the AgNPs@PDA film was transferred from PDMS to the LFP ridges to visualize a positive LFP pattern on the substrate, leaving behind a complementary (negative) LFP pattern on the PDMS flake. The compounds in the LFP were further analyzed via the AgNP-enhanced Raman technique. This approach enables high-contrast and full-feature visualization and transfer of LFP on arbitrary nonporous substrates and facilitates sensitive Raman analysis of multiple species in the sweat and thus promises great potential for practical applications.

Polydopamine thin film-assisted patterned chemical bath deposition of ZnO nanorods on arbitrary substrates

Patterned nanostructures tethered on various substrates are of essential importance for both fundamental research and practical application but often require tedious and expensive fabrication procedures.