9 Laser-Induced Forward Transfer Towards Additive Manufacturing
291
conductivity upon testing with acetone, methane, and ethanol [83]. Chemoselective
polymers have been also printed with LIFT on SAW sensors for the detection of toxic
volatile organic compounds (sarin, GB) [79]. In this work, chemical sensors based on
FBARs, in the solidly mounted resonator (SMR) configuration have been reported,
exploiting three polymer sensitive layers (LIFT printed) namely, polyepichlorohydrin
(PECH), polyethyleneimine (PEI), and polyisobutylene (PIB), with a detection limit
of 9.24 ppb for the PECH coated sensor when exposed to GB. Recently, graphene
oxide ink has been laser printed on Au electrodes on SiO 2 substrates, using the 4rth
harmonic of a pulsed Nd:YAG laser source and the printed features subsequently
underwent a thermal reduction step to restore the electrical properties of the graphitic
material [82]. The resistive chemical sensor devices were tested upon exposure to
water, ethanol, and p-xylene vapors and showed good response with a sensitivity of
5000 ppm for water vapors and 700 ppm for p-xylene vapors.
Regarding the incorporation of LIFT into the fabrication of biosensor devices, the
first work was reported by Karaiskou et al. [93], where lambda phage DNA microarrays were printed on glass substrates using LIFT. The ultrafast laser pulses were
generated by a sub-ps laser source (λ = 248 nm, f = 500 fs) and the transferred
structures had a 100 µm × 100 µm size. One year earlier, Ringeisen and co-workers
[91], have demonstrated the transfer of active proteins, viable Escherichia coli and
mammalian Chinese hamster ovary cells using a laser direct-write technique that
combined the LIFT and MAPLE techniques. After its first demonstration in biosensors fabrication, LIFT has been often used for the printing of biomaterials as in
the case of [92], where a novel laser printing approach has been reported. More
specifically, proteins and DNA have been laser transferred using a diode-pumped
ytterbium femtosecond laser (λ = 1027 nm, τ = 450 fs) from a tank that contained
the biomaterial solution and not a donor substrate as in the case of traditional LIFT.
In this case, the receiver substrate was transparent to the wavelength used and the
laser pulse went through the receiver substrate and was subsequently focused in the
tank containing the liquid solution causing micro-droplets to be ejected back towards
the receiver substrate (printing direction is in the opposite direction with respect to
the initial beam direction) in an approach similar to LIBT (Fig. 9.9).
Furthermore, skin cell lines (fibroblasts/keratinocytes) and human mesenchymal
stem cells have been transferred using LIFT owing to their potential use in regeneration of human skin applications as well as stem cell therapy [107]. In another work
involving the laser printing of cells, high throughput laser printing has been demonstrated [97], for the transfer of the biopolymer (sodium alginate), and biomaterials
(nano-sized hydroxyapatite synthesized by wet precipitation) and human endothelial cells (EA.hy926). This study demonstrated the potential of BioLP for threedimensional tissue construction applications. For the experiments, a rapid prototyping workstation equipped with an IR pulsed laser (τ = 30 ns, λ = 1064 nm)
was used. The transferred structures were 70 µm in diameter, where each droplet
contained 5–7 living cells. Another application that LIFT has been used, is point-ofcare medical diagnostics [104], where antibodies were laser transferred on cellulose
paper substrates that is an ideal receiver because of its bio-compatibility and liquid
transport properties. A calibration curve that related to the intensity of the color
291
conductivity upon testing with acetone, methane, and ethanol [83]. Chemoselective
polymers have been also printed with LIFT on SAW sensors for the detection of toxic
volatile organic compounds (sarin, GB) [79]. In this work, chemical sensors based on
FBARs, in the solidly mounted resonator (SMR) configuration have been reported,
exploiting three polymer sensitive layers (LIFT printed) namely, polyepichlorohydrin
(PECH), polyethyleneimine (PEI), and polyisobutylene (PIB), with a detection limit
of 9.24 ppb for the PECH coated sensor when exposed to GB. Recently, graphene
oxide ink has been laser printed on Au electrodes on SiO 2 substrates, using the 4rth
harmonic of a pulsed Nd:YAG laser source and the printed features subsequently
underwent a thermal reduction step to restore the electrical properties of the graphitic
material [82]. The resistive chemical sensor devices were tested upon exposure to
water, ethanol, and p-xylene vapors and showed good response with a sensitivity of
5000 ppm for water vapors and 700 ppm for p-xylene vapors.
Regarding the incorporation of LIFT into the fabrication of biosensor devices, the
first work was reported by Karaiskou et al. [93], where lambda phage DNA microarrays were printed on glass substrates using LIFT. The ultrafast laser pulses were
generated by a sub-ps laser source (λ = 248 nm, f = 500 fs) and the transferred
structures had a 100 µm × 100 µm size. One year earlier, Ringeisen and co-workers
[91], have demonstrated the transfer of active proteins, viable Escherichia coli and
mammalian Chinese hamster ovary cells using a laser direct-write technique that
combined the LIFT and MAPLE techniques. After its first demonstration in biosensors fabrication, LIFT has been often used for the printing of biomaterials as in
the case of [92], where a novel laser printing approach has been reported. More
specifically, proteins and DNA have been laser transferred using a diode-pumped
ytterbium femtosecond laser (λ = 1027 nm, τ = 450 fs) from a tank that contained
the biomaterial solution and not a donor substrate as in the case of traditional LIFT.
In this case, the receiver substrate was transparent to the wavelength used and the
laser pulse went through the receiver substrate and was subsequently focused in the
tank containing the liquid solution causing micro-droplets to be ejected back towards
the receiver substrate (printing direction is in the opposite direction with respect to
the initial beam direction) in an approach similar to LIBT (Fig. 9.9).
Furthermore, skin cell lines (fibroblasts/keratinocytes) and human mesenchymal
stem cells have been transferred using LIFT owing to their potential use in regeneration of human skin applications as well as stem cell therapy [107]. In another work
involving the laser printing of cells, high throughput laser printing has been demonstrated [97], for the transfer of the biopolymer (sodium alginate), and biomaterials
(nano-sized hydroxyapatite synthesized by wet precipitation) and human endothelial cells (EA.hy926). This study demonstrated the potential of BioLP for threedimensional tissue construction applications. For the experiments, a rapid prototyping workstation equipped with an IR pulsed laser (τ = 30 ns, λ = 1064 nm)
was used. The transferred structures were 70 µm in diameter, where each droplet
contained 5–7 living cells. Another application that LIFT has been used, is point-ofcare medical diagnostics [104], where antibodies were laser transferred on cellulose
paper substrates that is an ideal receiver because of its bio-compatibility and liquid
transport properties. A calibration curve that related to the intensity of the color