Polydimethylsiloxane Microwell Array Research Articles

A sandwiched photoelectrochemical sensor for high-throughput single-cell analysis based on low-toxic and near-infrared AgInS2 microarray

High-throughput single-cell quantitative analysis is becoming increasingly important to elucidate cellular heterogeneity and further understand some related disease mechanisms. Various techniques including mass spectrometry, fluorescence detection, and electrochemiluminescence analysis have made significant progress in this area, but their dilemma is the destruction of cellular activity, the introduction of exogenetic probes and the resulting cellular metabolism perturbation, or the steric hindrance of the cells to the substrate. Here, we develop a non-destructive, probe-free, and hindrance-free photoelectrochemical (PEC) single-cell microsensor. First, a patterned PEC microelectrode with low-toxic and near-infrared AgInS2 microdots is simply fabricated by using a polydimethylsiloxane (PDMS) microstencil, exhibiting high photoelectric efficiency and low S2- detection limit (1.0 nM). Then, a PDMS microwell array is prepared for single cells trapping, matching the size of the microelectrode and with high single-cell occupancy (>93%). Finally, a sealed sandwiching platform is formed by aligning and clamping the two arrays, each microdot contacts with a single cell in one microwell and reacts with the secreted H2S, preventing the neighboring microwell’s cross-contamination, cellular analyte’s dilution, and cell’s steric effect. The different light-addressable recorded photocurrent signals of all single cells directly reflect the 55.6% cell-to-cell differences. This report provides a useful and powerful tool to study single-cell heterogeneity.

Vacuum-Induced Wrinkle Arrays of InGaAs Semiconductor Nanomembranes on Polydimethylsiloxane Microwell Arrays

Tunable surface morphology in III-V semiconductor nanomembranes provides opportunities to modulate electronic structures and light interactions of semiconductors. Here, we introduce a vacuum-induced wrinkling method for the formation of ordered wrinkles in InGaAs nanomembranes (thickness, 42 nm) on PDMS microwell arrays as a strategy for deterministic and multidirectional wrinkle engineering of semiconductor nanomembranes. In this approach, a vacuum-induced pressure difference between the outer and inner sides of the microwell patterns covered with nanomembranes leads to bulging of the nanomembranes at the predefined microwells, which, in turn, results in stretch-induced wrinkle formation of the nanomembranes between the microwells. The direction and geometry of the nanomembrane wrinkles are well controlled by varying the PDMS modulus, depth, and shape of microwells, and the temperature during the transfer printing of nanomembrane onto heterogeneous substrates. The wrinkling method shown here can be applied to other semiconductor nanomembranes and may create an important platform to realize unconventional electronic devices with tunable electronic properties.

Trapping cells on a stretchable microwell array for single-cell analysis.

There is a need for a technology that can be incorporated into routine laboratory procedures to obtain a continuous, quantitative, fluorescence-based measurement of the dynamic behaviors of numerous individual living cells in parallel, while allowing other manipulations, such as staining, rinsing, and even retrieval of targeted cells. Here, we report a simple, low-cost microarray platform that can trap cells for dynamic single-cell analysis of mammalian cells. The elasticity of polydimethylsiloxane (PDMS) was utilized to trap tens of thousands of cells on an array. The PDMS microwell array was stretched by a tube through which cells were loaded on the array. Cells were trapped on the array by removal of the tube and relaxation of the PDMS. Once that was accomplished, the cells remained trapped on the array without continuous application of an external force and permitted subsequent manipulations, such as staining, rinsing, imaging, and even isolation of targeted cells. We demonstrate the utility of this platform by multicolor analysis of trapped cells and monitoring in individual cells real-time calcium flux after exposure to the calcium ionophore ionomycin. Additionally, a proof of concept for target cell isolation was demonstrated by using a microneedle to locally deform the PDMS membrane in order to retrieve a particular cell from the array.

Modular plastic chip for one-shot human papillomavirus diagnostic analysis

In this article, we report the design and development of a plastic modular chip suitable for one-shot human papillomavirus (HPV) diagnostics, namely detection of the viral presence and relative genotyping, by two sequential steps performed directly on the same device. The device is composed of two modular and disposable plastic units that can be assembled or used separately. The first module is represented by a polydimethylsiloxane (PDMS) microreactor that is exploited for real-time polymerase chain reaction (PCR) and, thus, is suitable for detecting the presence of virus. The second unit is a PDMS microwell array that allows virus genotyping by a colorimetric assay, based on DNA hybridization technology developed on plastic, requiring simple inspection by the naked eye. The two modules can be easily coupled to reusable hardware, enabling the heating/cooling processes and the real-time detection of HPV. By coupling real-time assay and colorimetric genotyping on the same chip, the assembled device may provide a low-cost tool for HPV diagnostics, thereby favoring the prediction of cancer risk in patients.