Fabrication and Testing of a Soft Shape Memory Alloy Actuator With an Integrated Liquid Metal Sensor

This paper introduces the fabrication and calibration of a soft shape memory alloy actuator with an integrated liquid metal sensor. The actuator is capable of transforming from an unactuated soft curled shape to an actuated rigid straight shape when it is electrically activated. The surface-bonded sensor is a capacitive strain gauge capable of tracking actuator curvature, which is composed of microfluidic channels of liquid metal alloy embedded in a soft silicone elastomer. The sensor has limited impact on the mechanical properties of the actuator due to being soft and lightweight. The fabrication procedure of the actuator is demonstrated in detail, and it is explained how the actuator can be easily fabricated using rapid prototyping techniques, such as laser cutting and stencil lithography. Then, the calibration procedure shows how the capacitance of the bonded strain gauge can be related to the actuator curvature by aligning capacitance data from the sensor with the actuator’s curvature captured by a fast camera. Finally, we implemented a closed-loop control strategy to show the effectiveness of the integrated sensor in improving the actuator performance. The used control scheme provides a method for optimizing actuation in a way that maximizes actuation amplitude. For optimal control, we use a learning-based approach with a covariant matrix adaptive evolutionary strategy (CMA-ES). It is shown that small change in either applied voltage or actuation time will lead to a large difference on the actuation performance.

Metal oxide QD based ultrasensitive microsphere fluorescent sensor for copper, chromium and iron ions in water

Herein we developed a rapid, cheap, and water-soluble ultra-sensitive ZnO quantum dot (QD) based metal sensor for detecting different hazardous metal ions up to the picomolar range in water.

Allosteric control of metal-responsive transcriptional regulators in bacteria

Many transition metals are essential trace nutrients for living organisms, but they are also cytotoxic in high concentrations. Bacteria maintain the delicate balance between metal starvation and toxicity through a complex network of metal homeostasis pathways. These systems are coordinated by the activities of metal-responsive transcription factors—also known as metal-sensor proteins or metalloregulators—that are tuned to sense the bioavailability of specific metals in the cell in order to regulate the expression of genes encoding proteins that contribute to metal homeostasis. Metal binding to a metalloregulator allosterically influences its ability to bind specific DNA sequences through a variety of intricate mechanisms that lie on a continuum between large conformational changes and subtle changes in internal dynamics. This review summarizes recent advances in our understanding of how metal sensor proteins respond to intracellular metal concentrations. In particular, we highlight the allosteric mechanisms used for metal-responsive regulation of several prokaryotic single-component metalloregulators, and we briefly discuss current open questions of how metalloregulators function in bacterial cells. Understanding the regulation and function of metal-responsive transcription factors is a fundamental aspect of metallobiochemistry and is important for gaining insights into bacterial growth and virulence.