Rachel Saunders

Inkjet printing biomaterials for tissue engineering: bioprinting

Abstract Inkjet printing offers controlled placement of both biological and synthetic materials. The precision, control and small working volumes associated with inkjet printing are advantageous where biological materials such as proteins, enzymes and cells can incur high costs. This review is primarily technology focused and divides bioprinting into three categories of interest: proteins, cells and scaffolds and demonstrates that the logistical hurdles and material formulation requirements remain a common denominator to the advancement of the field into commercial applications and three-dimensional (3-D) constructs. A variety of cell types printed using thermal, piezoelectric and electrostatic actuation mechanisms yield 80–95% cell viability. Transient membrane damage is reported for cells printed using a thermal printer. Protein deposition by thermal and piezoelectric printing results in reversible deformation leading to an increased need for the addition of ink modifiers. The fluid characteristics and the drop substrate interactions are identified as crucial with regards to future applications. The current approaches to scaffold matrix selection with regards to the complex criterion require fluid and solid phases and a controlled phase change while maintaining the criterion for printing vary from chemical gelation, physical gelation mechanisms (e.g. thermo reversible gels) and tandem gelation.

Ink Jet printing of mammalian primary cells for tissue engineering applications

Abstract : A piezoelectric drop on demand printer has been used to print primary human osteoblast and bovine chondrocyte cells. After deposition the cells were incubated at 37 deg C and characterised using optical microscopy, SEM and cell viability assays. Cells showed a robust response to printing exhibiting signs of proliferation and spreading. Increasing the drop velocity results in a reduced cell survival and proliferation rates but both cell types grew to confluence after printing under all conditions studied.

Current concepts and advances in the application of tissue engineering in otorhinolaryngology and head and neck surgery

OBJECTIVE This paper reviews the progress in the rapidly expanding scientific discipline of tissue engineering, which may have an integral role in the future of otorhinolaryngology. This article seeks to inform on the current concepts and principles of tissue engineering, and describe the state of the art research and developments in this exciting field as applied to ENT and head and neck surgery. METHOD In order to carry out a comprehensive review of the literature spanning the past 30 years, a search of relevant publications was performed using the Web of Knowledge, Medline and PubMed databases. RESULTS This search identified 85 scholarly articles, which were utilised as the basis of this review. CONCLUSION Given the current rate of development of tissue engineering research, it is likely that tissue-engineered implants will be widely used in surgical practice, including ENT and head and neck surgery.

Significant Factors in the Inkjet Manufacture of Frequency-Selective Surfaces

Additive fabrication of electromagnetic structures by inkjet printing technology is both cost effective and compatible with a wide range of environmentally friendly substrates, enabling the fabrication of frequency-selective surface (FSS) arrays with line dimensions less than 0.1 mm, which is difficult to achieve with conventional subtractive techniques. Several approaches, such as savings in ink by depositing it at the edges of dipole elements where the surface current tends to maximize, have been investigated in order to produce low-cost frequency-selective panels with acceptable level of isolation. The FSS transmission characteristics were improved by jetting multiple ink layers on the whole elements and at the edges. The electrical resistance of various arrays have been measured and analyzed and has been used to assess the performances of the FSS.

Piezoelectric inkjet printing of cells and biomaterials

Tissue engineering is a rapidly expanding field which aims to repair damaged tissue using a more regenerative approach. Technology has advanced to provide complex scaffolds with controlled architecture and porosity however problems with incorporating cells into the scaffold structure still persist. Standard cell seeding techniques can result in a poor cell seeding density, pore occlusion and is limited with regards to cell penetration, scaffold size and cell placement. Drop-on-demand inkjet printing is a fabrication technique which is capable of depositing materials layer-by-layer to form complex constructs. This technique has the potential to be used as a tool for the deposition of living cells. If this could be achieved then the simultaneous deposition of multiple cell types and scaffold matrix could yield a reality whereby human tissue could be fabricated with a precision not only applicable to scaffold architecture but also to the placement of multiple cell types. This work presents an insight into the effect of printing parameters on cell viability, deposition characteristics and explores methods of immobilization with an aim to achieve three-dimensions.

Five Day Attachment ECG Electrodes for Longitudinal Bio-Sensing Using Conformal Tattoo Substrates

State-of-the-art ECG (electrocardiography) uses wet Silver/Silver-Chloride (Ag/AgCl) electrodes, where a conductive gel is used to provide a resistive, low impedance, connection to the skin. These electrodes are very easy to apply, but have a significant number of limitations for personalized and preventative healthcare. In particular, that the gel dries out giving a limited connection time. This paper presents ECG electrodes manufactured using the inkjet printing of Silver nanoparticles onto a conformal tattoo substrate. The substrate maintains a high quality connection to the body for many days at a time allowing ECG monitoring over periods not previously possible without electrode re-attachment. The design and manufacture of the conformal electrodes is presented, together with detailed characterization of the electrode performance in terms of the signal to noise ratio and baseline wander. The signal to noise ratio is shown to still be over 30 dB five days after the initial electrode attachment.

Deficiencies in printed FSS intended for application in smart buildings

Errors occur in the process of digital printing of frequency selective screens using conductive inks. This paper describes some of the defects observed during the printing process and investigates their effect on the resonance frequencies of arrays that might be fabricated in practice. The elements are simple linear dipoles. The presence of the classes of error described would be serious in the case of elements with complex geometries.