Symposium SM03: Advanced Neural Materials and Devices

Jihwan Lee, University of California, San Diego

High Density, Individually Addressable Silicon-Based Nanowire Arrays Record Native Intracellular Activity from Primary Rodent Neurons without Electroporation

Written by Arun Kumar

Jihwan Lee from the University of California, San Diego says that many questions regarding neurons can be answered by looking at intracellular recordings from neurons and the neuronal networks. High spatiotemporal resolution and minimal invasiveness are essential requirements for understanding altered neuronal functions during diseased conditions and their response to drugs. The prevalently used method for probing intracellular potentials, the patch-clamp technique offers high signal fidelity but is limited in its throughput, scalability, and invasiveness. Planar microelectrode arrays can provide high throughput and a highly scalable process but are limited in their low signal fidelity. On the other hand, vertical nanowire arrays present an innovative nanoscale device providing high fidelity, throughput, and scalability.

Unlike prior nanoelectrode processes, Jihwan Lee states that their process does not involve any optoporation/electroporative technique to transiently permeate the cells and measure the intracellular potentials. This potentially helps reduce the damage caused to the cells. He states that their arrays can measure the native recording of graded potentials without attenuation of the signal amplitude during the experimentation. Increasing spike activity was recorded by the sensors during primary rat neuronal cell development and maturation. Lee also shows how the recorded spike activity and frequency of spikes vary during the addition of drugs. Apart from neurons, effective action potential measurements were also made from cultured cardiovascular progenitor cells. The non-electroporative, non-optoporative, sharp-nanowire array for intracellular sensing applications could be a cost-effective screening method for studying neuronal dynamics and neurological disease pathology.


Symposium SM08: Next-Generation Materials and Technologies for 3D Printing and Bioprinting

Jingjun Wu, Zhejiang University

Soft Hydrogels as Anti-Adhesion Interfaces for Rapid Digital Light 3D Printing

Written by Jessalyn Hui Ying Low

Bottom-up digital light processing (DLP) is a vat polymerization technique commonly used for three-dimensional (3D) printing applications; however, printing speed is limited by the adhesion between the cured part and curing window, limiting applications in large-scale manufacturing. In this talk, Jingjun Wu reports the use of soft and deformable hydrogels to achieve solid-solid, but soft interface between the two parts, which will allow for reduced separation force and high printing speeds.

Wu explains that this is achieved by adding the hydrogel interface between the liquid resin and bottom glass window. By decreasing the modulus and increasing the thickness of the hydrogel, separation force can be decreased. Using this hydrogel interface, lower separation forces were achieved as compared to using fluorinated ethylene propylene (FEP) interface, which is the technique commercially used. This lower separation force was attributed to the ability for localized deformation induced separation in the hydrogel interface, unlike in FEP. Furthermore, it was found that using a printer equipped with such hydrogel interface allowed for a high printing speed as fast as 400 mm/h. Wu shares that these hydrogels exhibited mechanical stability during printing as well as good compatibility with the resin. Importantly, printing resolution is not compromised, therefore making 3D printers with these soft hydrogels favorable for achieving rapid 3D printing.


Symposium NM07: Beyond Graphene 2D Materials—Synthesis, Properties and Device Applications

Ruifang Zhang, Purdue University

Late News: Atomically-Thin Tellurene Based Biosensor for Selective and Sensitive Electrochemical Detection of Dopamine

Written by Arun Kumar

Similar to Alzheimer’s or other neurodegenerative disorders, Parkinson’s is a chronic progressive disease where treatment options rely on a faster diagnosis. Parkinson’s affects an estimated 60,000 Americans every year. But unlike Alzheimer’s, Parkinson’s disease cannot be categorized with a single confirmatory test. The general practitioner is often required to look at the presented symptoms and rule out other disorders. But, Parkinson’s can be critically sensed by the altered release profile of the neurotransmitter dopamine in patients.

Ruifang Zhang from Purdue University presents a novel tellurene-based electrochemical biosensor that can be used as a cheap, highly selective, and sensitive alternative to quantitate dopamine levels in human plasma. For fabrication, first, a two-dimensional (2D) tellurene layer is placed over a glassy carbon electrode by a drop-casting method. Secondly, a quick in situ reduction is performed by immersing the material into a gold precursor solution to deposit gold nanoparticles over the surface. The fabricated biosensor is highly sensitive to dopamine levels through the effective interaction between nitrogen atoms on dopamine and the active tellurene surface. She says that an over-deposition of gold nanoparticles on the surface can negatively impact the device performance owing to the lower availability of active tellurene. So, the device optimization is based on several factors such as gold reaction time, tellurene width, and chloroauric acid concentration. A cheap and sensitive tool such as the tellurene-based biosensor can help in faster measurements of dopamine level changes for the clinical diagnosis of neurological disorders.


Symposium SM02: Next-Generation Antimicrobial Materials—Combating Multidrug Resistance and Biofilm Formation

Wanlin Xu, Université catholique de Louvain

Late News: Encapsulation of Bacteria in Membrane-Based Patches with Antibacterial Surface

Written by Jessalyn Hui Ying Low

Bacteria communities make up part of the skin microbiome, but bacteria imbalance could lead to various skin disorders. Therefore, exogenously delivering skin-beneficial bacteria is a favorable way to restore this balance. In this talk, Wanlin Xu reports the development of a membrane-based patch encapsulated with bacteria for this purpose.

Xu explains that to make these patches, bacteria, in this case staphylococcus epidermidis (S. epidermidis), is being encapsulated into the micropores of a porous membrane. This membrane is then coated with agarose gel, followed by surface modification for the purpose of controlling bacteria release. This surface modification is done by coating the gel with multilayer films containing antibacterial components through layer-by-layer (LbL) assembly. When the patch was coated with alginate/chitosan multilayer films, bacteria was released from the patch. However, when polyethylenimine/poly(styrenesulfonate) (PEI/PSS) polyelectrolyte multilayers were added, bacteria release was shown to be delayed, with lag time depending on the PEI/PSS thickness. Thus, this shows that by tuning the PEI/PSS surface modification of the membrane patch, bacteria metabolic activity and bacteria release can be controlled, making these patches promising for topical application of S. epidermidis.


Symposium EL07: Bioelectronics—Fundamentals and Applications

Anil Koklu, King Abdullah University Science and Technology

Late News: A Microfluidic and Nanoporous Membrane Integrated Organic Electrochemical Transistor for amyloid-β detection

Written by Arun Kumar

The underlying mechanisms behind Alzheimer’s are linked to the accumulated aggregates of a protein in the brain called amyloid-β (Aβ). Because Alzheimer’s disease is a chronic, progressive disease, a delayed diagnosis of the disease could lead to manifestations in the patient such as severe loss in thinking, learning, and fading memory. Anil Koklu suggests that the electronics field has an optimal solution for faster clinical diagnosis. Their group from the King Abdullah University Science and Technology have developed a microfluidic, nanoporous membrane integrated platform for efficient detection of Aβ peptide plaques in human serum.

Aβ has a high affinity toward congo red molecules. The detection system relies on the protein aggregates being captured in the nanoporous membranes and interacting with the congo red functionalized in the membranes. The organic electrochemical transistor (OECT) can then use this aggregate interaction to observe the modulating electric fields. Several semiconductive polymers were used to compare the efficiency and sensitivity of the OECT sensor to Aβ. Anil Koklu says that their microfluidic platform can detect protein aggregates at amounts as low as femtomolar concentrations, at a competitively higher sensitivity than previously mentioned literature. He expects that the study can be expanded to detect other proteins involved in the disease progression as well. Reinstating the introductory remark, as there is no approved cure for Alzheimer’s yet, a timely diagnosis of the disease often helps mitigate the late-stage symptoms. And this reason stimulates the interest in detection methods such as the OECT in the diagnostics market.


Symposium: EL01: Organic Semiconductors and Characterization Techniques for Emerging Electronic Devices

Chuanfei Wang, Linkoping University

Diluted Organic Semiconductor-Insulator Ternary Photovoltaics

Written by Victor A. Rodriguez-Toro

Typical in organic solar cells (OSCs) is the binary composition of the absorber of light: one of the semiconductors is typically named as the electron donor and the other as the electron acceptor. Ternary compositions have started being more explored with the synthesis of novel semiconductor materials (e.g., non-fullerene acceptors) with complementary absorption, usually in the near-infrared (NIR) region, as a strategy to increase the power conversion efficiency (PCE). In typical ternary absorbers, all the materials are semiconductors and the composition can be of either two donor materials and one acceptor materials or one donor material and two acceptor materials. 

Chuanfei Wang and co-workers present a variation of the ternary composition approach by using an insulator material instead of a semiconductor one as the third component of the absorber. They name this specific ternary material as a diluted organic semiconductor in which the polymer PBDB-T is used as the donor material, the polymer P(NDI20D-T2) as the acceptor material and the polymer PVK as the insulator material. The PCE of the ternary OSC is higher than the binary OSCs (in absence of the insulator material). Thermal and environmental stability is also enhanced in ternary OSCs, showing the potential of this approach.


Symposium SM07: Building Advanced Materials by Self-Assembly

Wenjie Zhou, Northwestern University

Colloidal Quasicrystals Engineered with DNA

Written by Jessalyn Hui Ying Low

Quasicrystals (QCs) are structures that are ordered but not periodic, and represent a class of materials that have gained significant experimental interest. However, many questions still remain in the field of colloidal quasicrystals, namely whether colloidal QCs can be formed from a single, uniformly-functionalized component. In this talk, Wenjie Zhou explains how by using DNA-mediated colloidal crystallization, he and his research team have formed the first known single-component colloidal dodecagonal quasicrystal (DDQC), which is also the first known colloidal QC from a uniformly-functionalized constituent.

To form these DDQCs, DNA-functionalized decahedral nanocrystals were used as building blocks. Despite the five-fold symmetry of decahedral nanocrystals which makes it difficult for periodic arrangement and close packing, it was found that through DNA-mediated colloidal crystallization, DDQCs could be formed. Interestingly, these QCs exhibited a 12-fold symmetry and not a ten-fold symmetry, which was validated through fast Fourier transformation (FFT) and small angle x-ray scattering profiles, and also corresponded to molecular dynamics (MD) simulation results to show a 12-fold axis.

Zhou also discusses the role of enthalpy and entropy in the formation of these DDQCs. When decahedral NCs underwent slow drying without DNA, DDQCs were not formed, but instead lattices of triclinic symmetry. As Zhou explains, QCs exhibit high facet contact, which is enthalpically favorable, since the maximization of DNA hybridization maximizes facet contact, while on the other hand, QCs exhibit low packing density, making it entropically unfavorable. This demonstrates how the enthalpy-driven nature of DNA crystal engineering is key to the formation of these DDQCs.


Symposium SM04: Beyond Nano-Challenges and Opportunities in Drug Delivery

Christine Jerome, University of Liege

Late News: Controlling Porosity and Protein Release Profile of Nanofibrillar Chitosan Scaffolds

Written by Jessalyn Hui Ying Low

Glioblastoma (GBM) is an aggressive form of brain cancer, where the first line of treatment is to surgically remove the tumor. However, this often leaves behind residual GBM cells, leading to a high tumor recurrence rate. In this talk, Christine Jerome reports the design of a nanofibrillar chitosan scaffold-based implant capable of trapping residual GBM cells. With this GBM cell trap, GBM cells will be recruited into the trap, where localized radiation can then be applied to kill the cells.

Jerome explains that this implant can be fabricated by electrospinning to form nanofibrillar mats out of chitosan. However, to serve its purpose as a cell trap, there are two key considerations. Firstly, porosity should be sufficiently high to allow cells to be recruited into the scaffold, while ensuring mechanical strength. Jerome reports that this can be achieved by using a metal honeycomb structure as collector for electrospinning rather than conventionally used aluminum foil. This allows for dense walls of fibers formed at the walls of the honeycomb structured nanofiber mat, thus preserving excellent mechanical properties, while having low fiber density in the alveolar, favorable for cell invasion. To enhance cell invasion, these mats can be further arranged into a multilayered scaffold.

The second consideration is to achieve controlled release of a chemoattractant from the scaffolds for cell recruitment. For this, SDF-1α, a chemokine, is encapsulated into poly(lactide-co-glycolide) (PLGA) nanoparticles, and introduced into the electrospinning solution. Nanoparticle encapsulation allowed for prolonged release of SDF-1α unlike free SDF-1α. Scanning electron micrographs also showed the successful dispersion of nanoparticles within the nanofiber mats. These nanofibrillar scaffolds are therefore promising implants as cell traps for GBM applications.  


Symposium: EL01: Organic Semiconductors and Characterization Techniques for Emerging Electronic Devices

Yongxi Li, University of Michigan

Color-Neutral, Semitransparent Organic Photovoltaics for Power Window Applications

Written by Victor A. Rodriguez-Toro

Power-generating window technologies would enable light in the visible range to be optically transmitted through the window, and light in the near-infrared (NIR) region to be absorbed by the window and transformed into electricity. Organic solar cells are promising candidates to enable this technology. However, organic materials, which can be very efficient absorbers in the NIR and transparent in the visible region, need to be found together with high conductivity transparent electrodes to attain semitransparent organic photovoltaic cells (ST-OPVs) with a high power conversion efficiency (PCE).

Yongxi Li and co-workers present an architecture which addresses all these challenges. This is achieved using (1) non-fullerene acceptor (NFA) derivatives as one of the absorbers; (2) a transparent electrode (top electrode) based on an alloy of copper (Cu) and silver (Ag); (3) an optical outcoupling (OC) structure, which increases the reflectivity of NIR light whereas it decreases the trapping of the light in the visible range. The OC structure is based on a small organic molecule (CBP) and magnesium fluoride (MgF2) and it is placed on top of the Cu-Ag transparent electrode; and (4) a bottom electrode based on glass, indium-tin oxide (ITO), and zinc oxide (ZnO), which is covered with an anti-reflective coating based on a bilayer of MgF2 and silicon dioxide (SO2). ST-OPVs with PCE up to 10.8% and a visible transparency of 50% approximately are demonstrated.


Symposium EL07: Bioelectronics—Fundamentals and Applications

Harika Dechiraju, University of California, Santa Cruz

A Microfluidic Ion Sensor Array

Written by Arun Kumar

Ion sensor applications are critical when monitoring and regulating cellular biological processes. Harika Dechiraju from the University of California, Santa Cruz demonstrates an Au/PEDOT:PSS-based microfluidic sensor array for ion-sensing applications. Current ion-selective membrane (ISM) patterning is performed by drop-casting onto the substrate because they are incompatible with the solvents used in the photolithographic technique. But with patterning emphasized with drop-casting, the feature size is limited to the area coated during the casting process. She states that the novelty of their microfluidic material arises from the way their nanosensor is fabricated. Their microfluidic-based method comprises a polydimethylsiloxane (PDMS) mold placed over the PEDOT:PSS electrode while the ISM solution is flown through the microfluidic channel. This enables patterning and miniaturization of nanosensing devices. Once the ISM is cured, the PDMS layer is removed and ion-sensitive applications can be performed. The selectivity of the sensor is tested with different electrolyte solutions containing sodium, potassium, and chloride ions. Different ion-selective membrane types are used with the sensor to obtain increased ion selectivity. The research group suggests that this microelectrode sensor array can be integrated with lab-on-a-chip models for easier monitoring of biological and physiological processes.