A template-synthesis method that enables fabrication of tapered microtube arrays is reported. Track-etched poly(ethylene terephthalate) membranes are used as the template, with closed-tipped conical pores having length and base diameter of 6.27 ± 0.28 and 1.21 ± 0.05 μm, respectively. A conductive layer of Pt is deposited by atomic layer deposition (ALD) to enable the successive electrodeposition of Ni. By decreasing the Pt precursor pulse duration from 10 to 1 s during the ALD step, the heights of the microtubes are controlled from the maximal full length (∼6 μm) to only a fraction (1–2 μm) of the template pore. Using a pulsed-current electrodeposition (PCD) method, a smooth and uniform Ni deposit is achieved with a thickness that can be controlled as a function of the PCD cycle. The microtubes’ lumen is confirmed to stay open even after 2000 cycles of Ni PCD. A potential application of the prepared array as a microinjection platform is demonstrated via successful injection of 10 nm sized CdZnS/ZnS core/shell quantum dots into Chlamydomonas reinhardtii microalgae cells with intact cell walls. The direct delivery method demonstrated in this paper offers novel opportunities for extending the growing interest in array-based microinjection platform to microalgal systems.Keywords: bionanotechnology; characterization tools; microstructures; quantum dots; thin films;

•Gold conical microneedle-array was prepared using the template synthesis method.•The microneedles can penetrate through the hard cell wall of C. reinhardtii.•C. reinhardtii expressed the recombinant genes delivered by the microneedle-array.In this paper, an array of conically shaped gold microneedles protruding from a substrate was prepared. We show for the first time, that such microneedles can penetrate through the intact cell wall of Chlamydomonas reinhardtii (C. reinhardtii), a unicellular plant organism. We demonstrate that this approach can be used to deliver a recombinant gene into the chloroplast of the C. reinhardtii. The microneedle array were coated with an orange fluorescence protein (OFP)—conferring gene, and the C. reinhardtii cells were deposited onto this array using centrifugal force. We show that the microneedle and the cells withstand the impact, and the gene is successfully delivered and expressed by the C. reinhardtii cells. The gene delivery method described here offers significant advantages relative to more conventional methods, which includes the ability to use microalgal cells with intact cell walls, and the ability to rapidly perform multiple transformations simultaneously through a simple centrifugal approach.

This paper demonstrates the first example of using generic Li-ion battery components (nickel, carboxymethylcellulose and styrene–butadiene rubber) to prepare piezoresistive materials (PRMs) which detect the strain of lithiating Sn in operando. The PRM was prepared by mixing the three components and molding it into a desired shape. Three different types of Ni microparticle arrangement strategies were investigated to study their effects on the piezoresistive performance: an alignment parallel to or perpendicular to the direction of strain, and no alignment (control and random dispersion). The alignment was directed by an external magnetic field during sample preparation and confirmed using cross-sectional SEM images. Significant differences were found between the different alignments, with the parallel alignment resulting in the lowest percolation threshold of 4 vol% Ni and perpendicular alignment the highest of 11 vol% Ni. For a fixed fraction of Ni microparticles at 4 vol%, the difference in alignment resulted in a difference in the gauge factor by three orders of magnitude. The stress–strain curve of the prepared PRMs showed a typical response seen for porous structures, which was consistent with the SEM images. The PRM samples are compatible with the low operating potential and the organic Li-ion electrolyte, and its porous structure allows electrolyte infusion that ensures the ionic conductivity of the material. Lithiation of Sn was successfully detected as a change in resistance using a parallelly aligned PRM with no additional treatment. The method described here offers significant merits over conventional approaches: the ability to directly monitor the strain without complex modelling, the simple low cost setup that does not require specialized equipment, and the ability to easily control the PRM performance by magnetically directed assembly.

•We report a simple bi-cell approach to synthesize polymer hydrogel thin films.•A heterogeneous reaction occurs at the surface of a nanoporous filter membrane.•No specialized instrumentation or intensive experimental steps are required.•Applying functional crosslinkers confers stimuli-responsiveness to synthesized film.•Exposure to glutathione and/or free amine groups degrades synthesized chitosan films.We report here a simple, versatile bi-cell-based platform for preparing crosslinked polymeric hydrogel thin films. Briefly, a nanoporous membrane is used to separate two solutions: one containing crosslinking molecules and the other containing oligomers. The crosslinking molecule diffuses through the membrane and reacts with the oligomer to form a polymeric film at the surface of the nanopore membrane. In this paper, a proof-of-concept experiment is described using crosslinkers with imidoester moieties (dimethyl 3,3′-dithiobispropionimidate (DTBP) or dimethyl suberimidate (DMS)) and chitosan oligomers. Crosslinking with DTBP or DMS also conferred degradability to the chitosan film. The film formation was confirmed and its morphology examined with electron microscopy. The chitosan film degradation was quantified by monitoring the transport of gold nanoparticles through the chitosan film after a degradation treatment. The film synthesis method presented here can potentially be used to prepare functional hydrogel thin films for biosensors, coatings and drug delivery systems in an inexpensive, high-throughput manner.

This paper demonstrates the first example of using generic Li-ion battery components (nickel, carboxymethylcellulose and styrene–butadiene rubber) to prepare piezoresistive materials (PRMs) which detect the strain of lithiating Sn in operando. The PRM was prepared by mixing the three components and molding it into a desired shape. Three different types of Ni microparticle arrangement strategies were investigated to study their effects on the piezoresistive performance: an alignment parallel to or perpendicular to the direction of strain, and no alignment (control and random dispersion). The alignment was directed by an external magnetic field during sample preparation and confirmed using cross-sectional SEM images. Significant differences were found between the different alignments, with the parallel alignment resulting in the lowest percolation threshold of 4 vol% Ni and perpendicular alignment the highest of 11 vol% Ni. For a fixed fraction of Ni microparticles at 4 vol%, the difference in alignment resulted in a difference in the gauge factor by three orders of magnitude. The stress–strain curve of the prepared PRMs showed a typical response seen for porous structures, which was consistent with the SEM images. The PRM samples are compatible with the low operating potential and the organic Li-ion electrolyte, and its porous structure allows electrolyte infusion that ensures the ionic conductivity of the material. Lithiation of Sn was successfully detected as a change in resistance using a parallelly aligned PRM with no additional treatment. The method described here offers significant merits over conventional approaches: the ability to directly monitor the strain without complex modelling, the simple low cost setup that does not require specialized equipment, and the ability to easily control the PRM performance by magnetically directed assembly.