3D Printed Electronics: Processes, Materials and Future Trends

The latest developments in smart systems for improved human lives with advanced biomedical devices have evolved out of multi-disciplinary scientific studies, including medicine, biology, material sciences, design, manufacturing, artificial intelligence, microelectronics, and so forth. The growth of such intelligent systems is primarily possible with innovative materials, which demonstrate the response to various external stimuli like temperature, heat, moisture, light, electromagnetic field, and chemical alteration. Such materials have been recently fabricated using different additive manufacturing techniques to devise personalized unique, complex, and novel structures that can adjust to external conditions over time and are specifically attributed to 4D printing. Novel materials that can further improve such systems continued to be explored and employed. This review paper investigates the additive manufacturing of functional polymer nanocomposites, which offer compliant structures with flexible manufacturing processes with high strength, low cost, and long-term stability. This study aims to deliver a comprehensive and deep understanding of the latest developments in materials, design, manufacturing, fundamental mechanisms involved, and future possibilities in this area of research. 

Additive manufacturing of smart polymeric composites: Literature review and future perspectives

3D printing of dual cross-linked hydrogel for fingerprint-like iontronic pressure sensor

Flexible mechanical sensors (e.g., strain, pressure, and force) fabricated primarily by printing technologies have emerged and evolved promptly in the past several years. 2D and 3D printing approaches enabled rapid prototyping of various flexible mechanical sensors that have demonstrated their unique applications in fields including robotics, human-machine interfaces, and biomedicine. Research efforts have primarily been focused on experimenting with different materials, device configurations, and sensing mechanisms to achieve better sensing performance. While great progress has been made, this field is still in its infancy where most research is exploratory; and even the performance standards and long-term objective/vision of these sensors are not clear. In this review, the state-of-the-art of three types of printed flexible mechanical sensors will be discussed and analyzed in terms of their fabrication methods, types of sensing materials and mechanisms, and challenges for future development.

Printed flexible mechanical sensors.

Vat photopolymerization of low-titanium lunar regolith simulant for optimal mechanical performance

Previous studies on UV-curable elastomer for digital light processing (DLP) 3D printing flexible electronics mostly focused on higher stretchability and healability, thereby ignoring rapid recovera...

3D printing highly stretchable conductors for flexible electronics with low signal hysteresis

Ku70 protein and topoisomerase IIα (Topo IIα) are promising targets of anticancer drugs, which play critical roles in DNA repair and replication processes. Three platinum(II) complexes, [PtCl(NH3)2(9-(pyridin-2-ylmethyl)-9H-carbazole)]NO3 (OPPC), [PtCl(NH3)2(9-(pyridin-3-ylmethyl)-9H-carbazole)]NO3 (MPPC), and [PtCl(NH3)2(9-(pyridin-4-ylmethyl)-9H-carbazole)]NO3 (PPPC), were designed as inhibitors of Ku70 and Topo IIα. Their antitumor activity and inhibitory efficacy on Ku70 and Topo IIα were investigated on cellular and molecular levels. OPPC exhibited high antiproliferative activity against various cancer cell lines, with acute toxicity to mice being lower than that of cisplatin. Moreover, OPPC could enter cancer cells effectively and cause DNA damage, which was evidenced by the enhanced expression of γ-H2AX, Chk1/2 phosphorylation, p53 and cell cycle arrest. OPPC also downregulated the DNA damage repair protein Ku70 and inhibited the formation of Ku70 foci-the central points or loci of Ku70, which would suppress DNA repair and induce a nonhomologous end joining response in cancer cells. More importantly, these complexes showed inhibition towards Topo IIα; in particular, OPPC was more effective than MPPC and PPPC. In the Topo IIα knockdown cells, Ku70 and Topo IIα were directly associated with the DNA damage and apoptotic response. The molecular docking provided detailed structural insights into the interactions of the complexes with Topo IIα. This study demonstrates that the cytotoxicity of these complexes is associated with the DNA damage and repair pathways mediated by Ku70 and Topo IIα; OPPC is an effective inhibitor of Ku70 and Topo IIα and restrains cancer cells via a mechanism utterly distinct from that of cisplatin.

Platinum complexes as inhibitors of DNA repair protein Ku70 and topoisomerase IIα in cancer cells.

Lupus nephritis (LN) is a type of immune-complex nephritis caused by systemic lupus erythematosus and is a major contributor to mortality and morbidity. Honokiol (HNK) has been found to have a therapeutic effect on LN, but its action mechanism remains unclear. In this study, we first demonstrated that HNK attenuates kidney injury in MRL/lpr mice. Results from RNA sequencing combined with ingenuity pathway analysis suggested that HNK plays an anti-LN role through inhibition of the NLRP3 inflammasome and IL33. GEO chip data, single-cell data, and clinical samples from LN patients demonstrated that the pyroptosis and IL-33/ST2 pathways are abnormally activated during the stage of LN. In vivo, similar to the results of the AAV-mediated NLRP3 shRNA MRL/lpr model, HNK downregulated serum and renal IL-33 levels, and suppressed NLRP3 inflammasome and the IL-33/ST2 axis in the kidney. In vitro, co-culturing NLRP3-overexpressing or IL-33 knocked-down rat renal macrophages with NRK-52E cells confirmed that NLRP3 activation in resident macrophages directly upregulates IL-33, which in turn mediates the IL-33/ST2/NF-κB pathway to promote the inflammatory response of renal tubular epithelial cells. Furthermore, a molecular docking model and surface plasmon resonance analysis were utilized to demonstrate a direct interaction between HNK and NLRP3. In conclusion, this study provides a novel anti-LN treatment strategy in which HNK plays a preventive and therapeutic role against LN by suppressing the abnormal crosstalk between renal resident macrophages and renal tubular epithelial cells by inhibiting the activation of the NLRP3/IL-33/ST2 axis. 

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Honokiol suppresses the aberrant interactions between renal resident macrophages and tubular epithelial cells in lupus nephritis through the NLRP3/IL-33/ST2 axis

In recent years, we have seen efforts made to monitor respiration for multiple users. Existing approaches capture chest movement relying on signals directly reflected from chest or separate breath waves based on breath rate difference between subjects. However, several limitations exist: 1) they may fail when subjects face away from the transceiver or are blocked by obstacles or other subjects; 2) they may fail to separate subjects' breath waves with the same or similar rates (i.e., breath rate difference < 1 bpm); 3) they assume a priori knowledge of number of subjects and cannot adapt to dynamic change of subject number during monitoring. To overcome these limitations, in this paper we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MultiResp</i> , a multi-user respiration monitoring system using acoustic signal. By fully leveraging the abundant acoustic signals reflected indirectly from subjects' chest, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MultiResp</i> can robustly capture chest movement even when they face away from the transceiver or are blocked. By extracting fine-grained breath rate and phase difference between different subjects, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MultiResp</i> can separate the breath waves with the same or similar rates and adapt to dynamic change of subject number during monitoring. Extensive experiments show that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MultiResp</i> is able to accurately monitor the respiration of multiple users with a median error of 0.3 bpm in various indoor scenarios, however, it fails when the sound pressure is lower than 55 dB or body movement is happening. 

Honghao Yan

Papers

3D printing highly stretchable conductors for flexible electronics with low signal hysteresis

3D printing of dual cross-linked hydrogel for fingerprint-like iontronic pressure sensor

Platinum complexes as inhibitors of DNA repair protein Ku70 and topoisomerase IIα in cancer cells.

Honokiol suppresses the aberrant interactions between renal resident macrophages and tubular epithelial cells in lupus nephritis through the NLRP3/IL-33/ST2 axis

MultiResp: Robust Respiration Monitoring for Multiple Users using Acoustic Signal