Over the past decade, boron‐doped diamond tips have become the ultimate choice for electrically characterizing microelectronics devices using scanning probe methods such as scanning spreading resistance microscopy (SSRM). Although nanometer‐scale electrical resolution has been demonstrated, the development of a reliable probe process remained a challenge. Therefore, we did develop in this work solid diamond tips with sub‐nanometer electrical resolution and integrated them into metal cantilevers using a peel‐off approach. It is shown that the ultra‐high tip resolution is achieved by diamond nanocrystals protruding from the apex of the diamond pyramid. The yield for sub‐nanometer probes is 20–30% in air and 40–60% in vacuum. This paper describes the fabrication scheme, discusses probe characterization, and shows SSRM measurements obtained with these probes. Our probes are routinely used for SSRM measurements and current efforts are focusing on increasing the yield for sub‐nanometer tips further.

The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80,000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.

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In this paper, we present preliminary results showing the response of glucose-sensitive hydrogels, confined in micro-pressure sensors, to the changes in environmental glucose concentration. The glucose concentrations were incrementally varied between 20 and 0mM in 0.15M PBS solution at 7.4 pH and bovine serum at 7.4 pH at room temperature and response of the sensor was recorded. The micro sensors demonstrate a response time of 10 minutes in both PBS and serum. Tissue response after 55 days of subcutaneous implantation of a EtO sterilized sensor in mice is presented. The preliminary analysis of the surrounding tissue shows inflammation which is believed not to interfere with the sensor performance.

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