19 Matching Annotations
  1. Apr 2021
    1. After the temperature was raised to room temperature, the chip components were pick-and-placed on the predefined contact pads. The placement accuracy was ensured using an optical microscope. Pouring polyimine solution on top and curing at room temperature for 48 hours, the LM circuitry and chip components were encapsulated.

      After the polyimine film was heated up, the chips could be placed and almost fused with the polyimine to keep them in place.

    2. To synthesize polyimine, terephthalaldehyde (1.5 g, 11.18 mmol), 3,3′-diamino-N-methyldipropylamine (1.251 g, 8.61 mmol), and tris(2-aminoethyl)amine (0.252 g, 1.72 mmol) were mixed in methanol (20 ml), as shown in fig. S2A.

      The specific polymers that are used to make up this polyimine.

    3. This process represents totally six different configurations. Optical microscope images in fig. S1C prove robust connection between the LM circuitry and the rigid chip components under extreme deformation.

      The authors look at the connection between the circuitry and the electronic parts to make sure that under this stress the parts are still communicating with each other.

    4. amine in methanol, the excessive amine monomers can react with the imine bonds inside the polyimine network

      When the electronic circuit is coated in this acid, the polyimine separates from the parts of the circuit. This allows the author to repair or replace any part of the circuit board instead of replacing the whole thing.

    5. . To further demonstrate the self-healing performance, the cutting and self-healing process at the same location of a polyimine encapsulated LM conductor was repeated five times.

      The author's cut the electronic circuit 5 times to prove that it can self heal through even being cut. The electronic circuit will repair itself after being cut.

    6. From FEA simulation, the maximum strain in the chip components is below 0.004%.

      The authors use the software FEA to mathematically model the max amount of strain that the device can withstand before the seal-healable nature fails.

    7. LM circuitry does not have fatigue issues, encapsulation does not affect the mechanical performance, and there is no stress concentration in the conductor at the interfaces between the rigid chip components and the soft substrate (fig. S1C).

      The authors test to see if the electronic circuit can keep up with the mechanical stress that is placed on the polyimine.

    8. To test biocompatibility, fig. S4 shows optical images comparing the skin conditions before (top left) and after wearing a polyimine film for 12 hours (bottom left) and 24 hours (bottom right), respectively. No noticeable adverse effects on the skin can be observed.

      The authors took pictures before and after wearing the sensor to see if the skin was affected by the polymer.

    9. Screen printing method is adopted to brush EGaIn LM against the mask, and peeling off of the mask leaves patterned LM traces on the polyimine substrate.

      Screen printing is a technique in which a mesh is used to transfer ink onto a substrate. In this case EGaln LM is used to transfer LM onto the polyimine.

  2. Mar 2021
    1. As demonstrated in Fig. 4A, when the LM circuit is cut broken by a razor blade (top frame), the ECG signal is lost (Fig. 4B, top). The top inset in Fig. 4A illustrates a magnified view of the broken LM conductor. After slightly pressing the two sides of the cut location, the LM conductor is self-healed, and the ECG sensor regains sensing capability

      The authors physically cut the LM circuit to determine that the EKG signal would be lost. Afterwards the two cut regions were slightly pressed together, and the LM material was self-healed. This allowed the ECG sensor to regain its sensing capability.

    2. The polyimine and LM were modeled as Neo-Hookean hyperelastic material using three-dimensional (3D) hybrid stress elements (C3D8H), and the chip components were modeled using elastic isotropic material with 3D stress elements (C3D8).

      The Polyimine and LM were 3D modeled on the software Abaqus. This software allowed the authors to determine the young's modulus and the Poisson ratio for each of the materials. These are important mechanical properties that allow the authors to model the mechanical behavior further.

    3. By 2021, the total electric waste is estimated to reach 52.2 million metric tons, and the majority of the waste cannot be appropriately recycled

      With an increase of electronic equipment production, it is rapidly becoming the fastest growing waste stream in the world. If this electronic waste is not handled correctly it could result in many health problems. Most of this electronic waste cannot be recycled. This paper discusses the uses of pyrometallurgical, hydrometallurgical, and biohydrometallurgical means to separate metals from electronic waste.

  3. Feb 2021
    1. Figure S5B shows the loading and unloading stress-strain curves of polyimine under cyclic loading test, which exhibits good elasticity with slight hysteresis

      The cyclic loading test is the repeated application of stress and strain to determine fatigue stress. The cyclic test for this experiment test the self-healing capacitates of the material, can the material go back to its original shape when stretched out. In this case, the polyimine had good elasticity, but exhibited some hysteresis. Hysteresis, in this case, is when the polyimine was stretched, but then had a small lag when returning to its original shape.

    2. A model reaction as shown in fig. S2B indicates that the imine bond exchange reaction is efficient at both room temperature and 80°C.

      Bond exchanges often are affected by temperature, and often times when bonds are heated up they can denature. It was important to test if hotter temperatures would affect the imine bond exchange reaction. The bonds were tested at room temperature and then 80 °C, the temperature did not affect the nature and effectiveness of the bond exchange reaction.

    3. As schematically illustrated in Fig. 1D, the cross-linked polyimine functions are based on the dynamic covalent chemistry principle

      The dynamic covalent chemistry principle states that when a system is under constant entropy then the system will start to approach a minimum value of internal energy. In this case, polyimine is constantly having its covalent bonds broken, which is the constant entropy, and this makes the internal energy of the polyimine lower. With this lower energy, it is easier to break and reattach the covalent bonds within the polyimine, meaning that self-healing is easier.

    4. As shown in fig. S2C, the high similarity between the FTIR spectra of the original and recycled polyimine supports the notion that these two films are chemically identical.

      FTIR stands for Fourier-transformed infrared spectroscopy, this technique is used to obtain absorption or emission of infrared light. In this case FTIR was used to determine if the original and recycled polyimine was chemically identical. If the length of the infrared waves are significantly different then that is a clear indicator that the substances have different chemical components. In this case, the length of the infrared waves are similar, meaning that this is the first indicator that the two materials are chemically similar.

    5. Among all the exciting applications, wearable electronics represents one of the most important, as it is the most accessible to people, and can be integrated onto the surface of human body to provide many useful functions, including physical activity tracking

      Dr. Xu and associates have developed a soft microfluidic sensor that could accommodate the human skin. The result was a soft sensor that could sit on the surface of the skin and monitor physiological markers wirelessly.

    6. It can be applied in places that are not accessible by traditional rigid printed circuit boards

      Dr. Choi and associates developed a nanocomposite made of silver and gold that optimizes conductivity and stretchability. This nanocomposite was used to make implantable implants that could integrate into the human skin.

    7. Stretchable/flexible electronics has attracted tremendous attention in the past two to three decades due to the combination of its superior mechanical attributes and electrical performance

      Dr. Gao and associates have developed a flexible wearable sensor that provides real time signals for certain biomarkers. Gao's devices analyzes sweat to determine real time data for glucose, lactose, electrolytes, and also the temperature of the skin.