In Case You Missed It

Adhesives

“Sustainably Sourced Components to Generate High-Strength Adhesives”

Authors: Clayton R. Westerman, et al.

Abstract: Nearly all adhesives are derived from petroleum, create permanent bonds, frustrate materials separation for recycling, and prevent degradation in landfills. When trying to shift from petroleum feedstocks to a sustainable materials ecosystem, available options suffer from low performance, high cost or lack of availability at the required scales. Here the authors present a sustainably sourced adhesive system, made from epoxidized soy oil, malic acid and tannic acid, with performance comparable to that of current industrial products. Joints can be cured under conditions ranging from use of a hair dryer for 5 min. to an oven at 180 °C for 24 hr. Adhesion between metal substrates up to around 18MPa is achieved, and, in the best cases, performance exceeds that of a classic epoxy, the strongest modern adhesive. All components are biomass derived, low cost and already available in large quantities. Manufacturing at scale can be a simple matter of mixing and heating, suggesting that this new adhesive may contribute towards the sustainable bonding of materials. (Nature, Sept. 13, 2023, https://www.nature.com/articles/s41586-023-06335-7)

Impedance Measurement

“Design, Implementation, and Characterization of a Compact Lock-in Add-on for Low-Frequency Impedance Measurements”

Authors: Sara Pettinato, et. al.

Abstract: The authors present a cost-effective compact solution for ultra-low-frequency impedance measurements, operating in a wide range, from 1mHz to 250kHz. Coupled to a lock-in amplifier, the designed circuit is based on a Howland current pump cascaded by a precision current divider to set the conversion factor at 100nA/V, 1µA/V, or 100µA/V. Therefore, it is possible to generate very low-current signals to measure resistive impedances up to 100MΩ. In addition, a feedback network is inserted to null the voltage drift induced by leakage currents and offset voltages, thus permitting measurement of low-capacitance loads, experimentally tested down to 10nF. Remarkably, the feedback network allows measurements in the presence of high voltage bias of the load, and experimental results performed up to 60V demonstrate the excellent stability of the designed system, thus a high voltage compliance. The proposed circuit is particularly interesting for the conditioning of both resistive and capacitive sensors and it is likely to be an effective solution for implementation of a portable instrument for measuring signals from biosensors. (Electronics, August 2023, https://doi.org/10.3390/electronics12163406)

Medical Electronics

“A System for Bioelectronic Delivery of Treatment Directed Toward Wound Healing”

Authors: Prabhat Baniya, et al.

Abstract: Researchers developed a wearable system for bioelectronic delivery of treatment directed toward wound healing. The system consisted of a 3-D printed custom polydimethylsiloxane (PDMS) delivery device integrated with a printed circuit board. Both the PCB and the PDMS had corresponding through-holes with metal connection pins covered in silver epoxy, permitting physical and electric integration. The modularly built system included solution-containing reservoirs, implanted electrodes, and capillary tubes filled with hydrogels.

The team demonstrated three designs for the PCB component: one wired and the other two powered by batteries with as well as without inbuilt memory. The PCB wired version used an externally located voltage controller to activate the device, whereas the one powered by batteries used a microcontroller unit (MCU) that enabled programmed voltages to be applied, as well as a deep sleep module to extend battery lifetime. The PCB powered by batteries with inbuilt memory was used to document delivered currents, enabling the verification of the therapeutic dosage delivered.

The devices were delivered hydrogen ions in C57B6 and wild-type murine models in vivo, and fluoxetine was delivered using simulated wound environments ex vivo. The PDMS was employed as a bridge between biological specimens such as a wound site and typical electrical components. Once a positive voltage was applied across the reference (RE) and working electrodes (WE), drug ions were pulled through the working electrode to the wound site as a substitute for indigenous sodium ions at the reference electrode. Each PCB included four actuation pathways wherein current could be measured by connecting resistors in parallel with voltages supplied via the MCU or an externally located controller. The wired system relied on connecting the PCB to an external voltage controller and included computer-aided design (CAD) assemblies of the PDMS and PCB subsystems. (Scientific Reports, Sept. 7, 2023, https://doi.org/10.1038/s41598-023-41572-w)

Soldering

“Lower Temperature Soldering Using Supercooled Liquid Metal”

Authors: Ian Tevis and Dipak Paramanik

Abstract: Lead-free solder metal alloys can be formed into supercooled liquid metal microcapsules and used to create solid full metal interconnects at dramatically lower processing temperatures. These alloys can be made with or without bismuth. The technology encapsulates known and established RoHS compliant solder alloys inside a thin oxide/organic shell nanofilm that keeps the metal in a metastable supercooled liquid state at ambient temperatures. The thin oxide/organic shell can be mechanically broken or chemically dissolved to release the liquid metal that then rapidly solidifies all without requiring heat. The novel solder interconnect technology avoids thermal damage to components and materials, or quality issues caused by coefficient of thermal expansion mismatch. (Journal of Surface Mount Technology, July 2023, https://doi.org/10.37665/smt.v36i2.36)